]> git.ozlabs.org Git - ccan/blobdiff - ccan/tdb/tools/replay_trace.c
tdb: fix test helper to include own header, fix function definition.
[ccan] / ccan / tdb / tools / replay_trace.c
index f697a13787995395df869c2c742c46857ce5f13e..b42fb7b1b5e61e43858679a0b21e64f2ac66122f 100644 (file)
 #include <sys/types.h>
 #include <sys/wait.h>
 #include <sys/time.h>
+#include <errno.h>
+#include <signal.h>
+#include <assert.h>
+#include <fcntl.h>
 
 #define STRINGIFY2(x) #x
 #define STRINGIFY(x) STRINGIFY2(x)
 
+static bool quiet = false;
+
 /* Avoid mod by zero */
 static unsigned int total_keys = 1;
 
+/* All the wipe_all ops. */
+static struct op_desc *wipe_alls = NULL;
+static unsigned int num_wipe_alls = 0;
+
 /* #define DEBUG_DEPS 1 */
 
+/* Traversals block transactions in the current implementation. */
+#define TRAVERSALS_TAKE_TRANSACTION_LOCK 1
+
 struct pipe {
        int fd[2];
 };
 static struct pipe *pipes;
+static int backoff_fd = -1;
 
 static void __attribute__((noreturn)) fail(const char *filename,
                                           unsigned int line,
@@ -45,7 +59,8 @@ static void __attribute__((noreturn)) fail(const char *filename,
        do {                                                            \
                int ret = (expr);                                       \
                if (ret != (expect))                                    \
-                       fail(filename, i+1, STRINGIFY(expr) "= %i", ret); \
+                       fail(filename[file], i+1,                       \
+                            STRINGIFY(expr) "= %i", ret);              \
        } while (0)
 
 /* Try or imitate results. */
@@ -54,7 +69,8 @@ static void __attribute__((noreturn)) fail(const char *filename,
                int ret = expr;                                         \
                if (ret != expect) {                                    \
                        fprintf(stderr, "%s:%u: %s gave %i not %i",     \
-                             filename, i+1, STRINGIFY(expr), ret, expect); \
+                               filename[file], i+1, STRINGIFY(expr),   \
+                               ret, expect);                           \
                        if (expect == 0)                                \
                                force;                                  \
                        else                                            \
@@ -98,7 +114,6 @@ enum op_type {
        OP_TDB_CHAINUNLOCK,
        OP_TDB_CHAINLOCK_READ,
        OP_TDB_CHAINUNLOCK_READ,
-       OP_TDB_INCREMENT_SEQNUM_NONBLOCK,
        OP_TDB_PARSE_RECORD,
        OP_TDB_EXISTS,
        OP_TDB_STORE,
@@ -107,35 +122,52 @@ enum op_type {
        OP_TDB_WIPE_ALL,
        OP_TDB_TRANSACTION_START,
        OP_TDB_TRANSACTION_CANCEL,
+       OP_TDB_TRANSACTION_PREPARE_COMMIT,
        OP_TDB_TRANSACTION_COMMIT,
        OP_TDB_TRAVERSE_READ_START,
        OP_TDB_TRAVERSE_START,
        OP_TDB_TRAVERSE_END,
        OP_TDB_TRAVERSE,
+       OP_TDB_TRAVERSE_END_EARLY,
        OP_TDB_FIRSTKEY,
        OP_TDB_NEXTKEY,
        OP_TDB_FETCH,
        OP_TDB_DELETE,
+       OP_TDB_REPACK,
 };
 
 struct op {
-       unsigned int serial;
-       enum op_type op;
+       unsigned int seqnum;
+       enum op_type type;
        TDB_DATA key;
        TDB_DATA data;
        int ret;
+
        /* Who is waiting for us? */
        struct list_head post;
-       /* How many are we waiting for? */
-       unsigned int pre;
+       /* What are we waiting for? */
+       struct list_head pre;
+
+       /* If I'm part of a group (traverse/transaction) where is
+        * start?  (Otherwise, 0) */
+       unsigned int group_start;
 
        union {
                int flag; /* open and store */
-               struct traverse *trav; /* traverse start */
-               TDB_DATA post_append; /* append */
+               struct {  /* append */
+                       TDB_DATA pre;
+                       TDB_DATA post;
+               } append;
+               /* transaction/traverse start/chainlock */
+               unsigned int group_len;
        };
 };
 
+struct op_desc {
+       unsigned int file;
+       unsigned int op_num;
+};
+
 static unsigned char hex_char(const char *filename, unsigned int line, char c)
 {
        c = toupper(c);
@@ -172,206 +204,278 @@ static TDB_DATA make_tdb_data(const void *ctx,
 }
 
 static void add_op(const char *filename, struct op **op, unsigned int i,
-                  unsigned int serial, enum op_type type)
+                  unsigned int seqnum, enum op_type type)
 {
        struct op *new;
        *op = talloc_realloc(NULL, *op, struct op, i+1);
        new = (*op) + i;
-       new->op = type;
-       new->serial = serial;
-       new->pre = 0;
+       new->type = type;
+       new->seqnum = seqnum;
        new->ret = 0;
+       new->group_start = 0;
 }
 
-static void op_add_nothing(const char *filename,
-                          struct op op[], unsigned int op_num, char *words[])
+static void op_add_nothing(char *filename[], struct op op[],
+                          unsigned file, unsigned op_num, char *words[])
 {
        if (words[2])
-               fail(filename, op_num+1, "Expected no arguments");
+               fail(filename[file], op_num+1, "Expected no arguments");
        op[op_num].key = tdb_null;
 }
 
-static void op_add_key(const char *filename,
-                      struct op op[], unsigned int op_num, char *words[])
+static void op_add_key(char *filename[], struct op op[],
+                      unsigned file, unsigned op_num, char *words[])
 {
        if (words[2] == NULL || words[3])
-               fail(filename, op_num+1, "Expected just a key");
+               fail(filename[file], op_num+1, "Expected just a key");
 
-       op[op_num].key = make_tdb_data(op, filename, op_num+1, words[2]);
-       if (op[op_num].op != OP_TDB_TRAVERSE)
-               total_keys++;
+       op[op_num].key = make_tdb_data(op, filename[file], op_num+1, words[2]);
+       total_keys++;
 }
 
-static void op_add_key_ret(const char *filename,
-                          struct op op[], unsigned int op_num, char *words[])
+static void op_add_key_ret(char *filename[], struct op op[],
+                          unsigned file, unsigned op_num, char *words[])
 {
        if (!words[2] || !words[3] || !words[4] || words[5]
            || !streq(words[3], "="))
-               fail(filename, op_num+1, "Expected <key> = <ret>");
+               fail(filename[file], op_num+1, "Expected <key> = <ret>");
        op[op_num].ret = atoi(words[4]);
-       op[op_num].key = make_tdb_data(op, filename, op_num+1, words[2]);
+       op[op_num].key = make_tdb_data(op, filename[file], op_num+1, words[2]);
        /* May only be a unique key if it fails */
        if (op[op_num].ret != 0)
                total_keys++;
 }
 
-static void op_add_key_data(const char *filename,
-                           struct op op[], unsigned int op_num, char *words[])
+static void op_add_key_data(char *filename[], struct op op[],
+                           unsigned file, unsigned op_num, char *words[])
 {
        if (!words[2] || !words[3] || !words[4] || words[5]
            || !streq(words[3], "="))
-               fail(filename, op_num+1, "Expected <key> = <data>");
-       op[op_num].key = make_tdb_data(op, filename, op_num+1, words[2]);
-       op[op_num].data = make_tdb_data(op, filename, op_num+1, words[4]);
-       /* May only be a unique key if it fails */
+               fail(filename[file], op_num+1, "Expected <key> = <data>");
+       op[op_num].key = make_tdb_data(op, filename[file], op_num+1, words[2]);
+       op[op_num].data = make_tdb_data(op, filename[file], op_num+1, words[4]);
+       /* Likely only be a unique key if it fails */
        if (!op[op_num].data.dptr)
                total_keys++;
+       else if (random() % 2)
+               total_keys++;
 }
 
-/* <serial> tdb_store <rec> <rec> <flag> = <ret> */
-static void op_add_store(const char *filename,
-                        struct op op[], unsigned int op_num, char *words[])
+/* We don't record the keys or data for a traverse, as we don't use them. */
+static void op_add_traverse(char *filename[], struct op op[],
+                           unsigned file, unsigned op_num, char *words[])
+{
+       if (!words[2] || !words[3] || !words[4] || words[5]
+           || !streq(words[3], "="))
+               fail(filename[file], op_num+1, "Expected <key> = <data>");
+       op[op_num].key = tdb_null;
+}
+
+/* Full traverse info is useful for debugging, but changing it to
+ * "traversefn" without the data makes the traces *much* smaller! */
+static void op_add_traversefn(char *filename[], struct op op[],
+                           unsigned file, unsigned op_num, char *words[])
+{
+       if (words[2])
+               fail(filename[file], op_num+1, "Expected no values");
+       op[op_num].key = tdb_null;
+}
+
+/* <seqnum> tdb_store <rec> <rec> <flag> = <ret> */
+static void op_add_store(char *filename[], struct op op[],
+                        unsigned file, unsigned op_num, char *words[])
 {
        if (!words[2] || !words[3] || !words[4] || !words[5] || !words[6]
            || words[7] || !streq(words[5], "="))
-               fail(filename, op_num+1, "Expect <key> <data> <flag> = <ret>");
+               fail(filename[file], op_num+1, "Expect <key> <data> <flag> = <ret>");
 
        op[op_num].flag = strtoul(words[4], NULL, 0);
        op[op_num].ret = atoi(words[6]);
-       op[op_num].key = make_tdb_data(op, filename, op_num+1, words[2]);
-       op[op_num].data = make_tdb_data(op, filename, op_num+1, words[3]);
+       op[op_num].key = make_tdb_data(op, filename[file], op_num+1, words[2]);
+       op[op_num].data = make_tdb_data(op, filename[file], op_num+1, words[3]);
        total_keys++;
 }
 
-/* <serial> tdb_append <rec> <rec> = <rec> */
-static void op_add_append(const char *filename,
-                         struct op op[], unsigned int op_num, char *words[])
+/* <seqnum> tdb_append <rec> <rec> = <rec> */
+static void op_add_append(char *filename[], struct op op[],
+                         unsigned file, unsigned op_num, char *words[])
 {
        if (!words[2] || !words[3] || !words[4] || !words[5] || words[6]
            || !streq(words[4], "="))
-               fail(filename, op_num+1, "Expect <key> <data> = <rec>");
+               fail(filename[file], op_num+1, "Expect <key> <data> = <rec>");
+
+       op[op_num].key = make_tdb_data(op, filename[file], op_num+1, words[2]);
+       op[op_num].data = make_tdb_data(op, filename[file], op_num+1, words[3]);
+
+       op[op_num].append.post
+               = make_tdb_data(op, filename[file], op_num+1, words[5]);
 
-       op[op_num].key = make_tdb_data(op, filename, op_num+1, words[2]);
-       op[op_num].data = make_tdb_data(op, filename, op_num+1, words[3]);
-       op[op_num].post_append
-               = make_tdb_data(op, filename, op_num+1, words[5]);
+       /* By subtraction, figure out what previous data was. */
+       op[op_num].append.pre.dptr = op[op_num].append.post.dptr;
+       op[op_num].append.pre.dsize
+               = op[op_num].append.post.dsize - op[op_num].data.dsize;
        total_keys++;
 }
 
-/* <serial> tdb_get_seqnum = <ret> */
-static void op_add_seqnum(const char *filename,
-                         struct op op[], unsigned int op_num, char *words[])
+/* <seqnum> tdb_get_seqnum = <ret> */
+static void op_add_seqnum(char *filename[], struct op op[],
+                         unsigned file, unsigned op_num, char *words[])
 {
        if (!words[2] || !words[3] || words[4] || !streq(words[2], "="))
-               fail(filename, op_num+1, "Expect = <ret>");
+               fail(filename[file], op_num+1, "Expect = <ret>");
 
        op[op_num].key = tdb_null;
        op[op_num].ret = atoi(words[3]);
 }
 
-static void op_add_traverse(const char *filename,
-                           struct op op[], unsigned int op_num, char *words[])
+static void op_add_traverse_start(char *filename[], struct op op[],
+                                 unsigned file, unsigned op_num, char *words[])
 {
        if (words[2])
-               fail(filename, op_num+1, "Expect no arguments");
+               fail(filename[file], op_num+1, "Expect no arguments");
 
        op[op_num].key = tdb_null;
-       op[op_num].trav = NULL;
+       op[op_num].group_len = 0;
 }
 
-struct traverse_hash {
-       TDB_DATA key;
-       unsigned int index;
-};
+static void op_add_transaction(char *filename[], struct op op[],
+                              unsigned file, unsigned op_num, char *words[])
+{
+       if (words[2])
+               fail(filename[file], op_num+1, "Expect no arguments");
 
-/* A traverse is a hash of keys, each one associated with ops. */
-struct traverse {
-       /* How many traversal callouts should I do? */
-       unsigned int num;
+       op[op_num].key = tdb_null;
+       op[op_num].group_len = 0;
+}
 
-       /* Where is traversal end op? */
-       unsigned int end;
+static void op_add_chainlock(char *filename[], struct op op[],
+                            unsigned file, unsigned op_num, char *words[])
+{
+       if (words[2] == NULL || words[3])
+               fail(filename[file], op_num+1, "Expected just a key");
 
-       /* For trivial traversals. */
-       struct traverse_hash *hash;
-};
+       /* A chainlock key isn't a key in the normal sense; it doesn't
+        * have to be in the db at all.  Also, we don't want to hash this op. */
+       op[op_num].data = make_tdb_data(op, filename[file], op_num+1, words[2]);
+       op[op_num].key = tdb_null;
+       op[op_num].group_len = 0;
+}
 
-/* A trivial traversal is one which doesn't terminate early and only
- * plays with its own record.  We can reliably replay these even if
- * traverse order changes. */
-static bool is_trivial_traverse(struct op op[], unsigned int end)
+static void op_add_chainlock_ret(char *filename[], struct op op[],
+                                unsigned file, unsigned op_num, char *words[])
 {
-#if 0
-       unsigned int i;
-       TDB_DATA cur = tdb_null;
+       if (!words[2] || !words[3] || !words[4] || words[5]
+           || !streq(words[3], "="))
+               fail(filename[file], op_num+1, "Expected <key> = <ret>");
+       op[op_num].ret = atoi(words[4]);
+       op[op_num].data = make_tdb_data(op, filename[file], op_num+1, words[2]);
+       op[op_num].key = tdb_null;
+       op[op_num].group_len = 0;
+       total_keys++;
+}
 
-       if (op[end].ret != 0)
-               return false;
+static void op_add_wipe_all(char *filename[], struct op op[],
+                           unsigned file, unsigned op_num, char *words[])
+{
+       if (words[2])
+               fail(filename[file], op_num+1, "Expected no arguments");
+       op[op_num].key = tdb_null;
+       wipe_alls = talloc_realloc(NULL, wipe_alls, struct op_desc,
+                                  num_wipe_alls+1);
+       wipe_alls[num_wipe_alls].file = file;
+       wipe_alls[num_wipe_alls].op_num = op_num;
+       num_wipe_alls++;
+}
 
-       for (i = 0; i < end; i++) {
-               if (!op[i].key.dptr)
-                       continue;
-               if (op[i].op == OP_TDB_TRAVERSE)
-                       cur = op[i].key;
-               if (!key_eq(cur, op[i].key))
-                       return false;
+static int op_find_start(struct op op[], unsigned int op_num, enum op_type type)
+{
+       unsigned int i;
+
+       for (i = op_num-1; i > 0; i--) {
+               if (op[i].type == type && !op[i].group_len)
+                       return i;
        }
-       return true;
-#endif
-       /* With multiple things happening at once, no traverse is trivial. */
-       return false;
+       return 0;
 }
 
-static void op_analyze_traverse(const char *filename,
-                               struct op op[], unsigned int op_num,
-                               char *words[])
+static void op_analyze_transaction(char *filename[], struct op op[],
+                                  unsigned file, unsigned op_num,
+                                  char *words[])
 {
-       int i;
-       struct traverse *trav = talloc(op, struct traverse);
+       unsigned int start, i;
+
+       op[op_num].key = tdb_null;
+
+       if (words[2])
+               fail(filename[file], op_num+1, "Expect no arguments");
+
+       start = op_find_start(op, op_num, OP_TDB_TRANSACTION_START);
+       if (!start)
+               fail(filename[file], op_num+1, "no transaction start found");
+
+       op[start].group_len = op_num - start;
+
+       /* This rolls in nested transactions.  I think that's right. */
+       for (i = start; i <= op_num; i++)
+               op[i].group_start = start;
+}
+
+/* We treat chainlocks a lot like transactions, even though that's overkill */
+static void op_analyze_chainlock(char *filename[], struct op op[],
+                                unsigned file, unsigned op_num, char *words[])
+{
+       unsigned int i, start;
+
+       if (words[2] == NULL || words[3])
+               fail(filename[file], op_num+1, "Expected just a key");
+
+       op[op_num].data = make_tdb_data(op, filename[file], op_num+1, words[2]);
+       op[op_num].key = tdb_null;
+       total_keys++;
+
+       start = op_find_start(op, op_num, OP_TDB_CHAINLOCK);
+       if (!start)
+               start = op_find_start(op, op_num, OP_TDB_CHAINLOCK_READ);
+       if (!start)
+               fail(filename[file], op_num+1, "no initial chainlock found");
+
+       /* FIXME: We'd have to do something clever to make this work
+        * vs. deadlock. */
+       if (!key_eq(op[start].data, op[op_num].data))
+               fail(filename[file], op_num+1, "nested chainlock calls?");
+
+       op[start].group_len = op_num - start;
+       for (i = start; i <= op_num; i++)
+               op[i].group_start = start;
+}
+
+static void op_analyze_traverse(char *filename[], struct op op[],
+                               unsigned file, unsigned op_num, char *words[])
+{
+       int i, start;
+
+       op[op_num].key = tdb_null;
 
        /* = %u means traverse function terminated. */
        if (words[2]) {
                if (!streq(words[2], "=") || !words[3] || words[4])
-                       fail(filename, op_num+1, "expect = <num>");
+                       fail(filename[file], op_num+1, "expect = <num>");
                op[op_num].ret = atoi(words[3]);
        } else
                op[op_num].ret = 0;
 
-       trav->num = 0;
-       trav->end = op_num;
-       for (i = op_num-1; i >= 0; i--) {
-               if (op[i].op == OP_TDB_TRAVERSE)
-                       trav->num++;
-               if (op[i].op != OP_TDB_TRAVERSE_READ_START
-                   && op[i].op != OP_TDB_TRAVERSE_START)
-                       continue;
-               if (op[i].trav)
-                       continue;
-               break;
-       }
-
-       if (i < 0)
-               fail(filename, op_num+1, "no traversal start found");
+       start = op_find_start(op, op_num, OP_TDB_TRAVERSE_START);
+       if (!start)
+               start = op_find_start(op, op_num, OP_TDB_TRAVERSE_READ_START);
+       if (!start)
+               fail(filename[file], op_num+1, "no traversal start found");
 
-       op[i].trav = trav;
+       op[start].group_len = op_num - start;
 
-       if (is_trivial_traverse(op+i, op_num-i)) {
-               /* Fill in a plentiful hash table. */
-               op[i].trav->hash = talloc_zero_array(op[i].trav,
-                                                    struct traverse_hash,
-                                                    trav->num * 2);
-               for (; i < op_num; i++) {
-                       unsigned int h;
-                       if (op[i].op != OP_TDB_TRAVERSE)
-                               continue;
-                       h = hash_key(&op[i].key) % (trav->num * 2);
-                       while (trav->hash[h].index)
-                               h = (h + 1) % (trav->num * 2);
-                       trav->hash[h].index = i+1;
-                       trav->hash[h].key = op[i].key;
-               }
-       } else
-               trav->hash = NULL;
+       /* Don't roll in nested traverse/chainlock */
+       for (i = start; i <= op_num; i++)
+               if (!op[i].group_start)
+                       op[i].group_start = start;
 }
 
 /* Keep -Wmissing-declarations happy: */
@@ -380,6 +484,105 @@ find_keyword (register const char *str, register unsigned int len);
 
 #include "keywords.c"
 
+struct depend {
+       /* We can have more than one */
+       struct list_node pre_list;
+       struct list_node post_list;
+       struct op_desc needs;
+       struct op_desc prereq;
+};
+
+static void check_deps(const char *filename, struct op op[], unsigned int num)
+{
+#ifdef DEBUG_DEPS
+       unsigned int i;
+
+       for (i = 1; i < num; i++)
+               if (!list_empty(&op[i].pre))
+                       fail(filename, i+1, "Still has dependencies");
+#endif
+}
+
+static void dump_pre(char *filename[], struct op *op[],
+                    unsigned int file, unsigned int i)
+{
+       struct depend *dep;
+
+       if (!quiet) {
+               printf("%s:%u (%u) still waiting for:\n", filename[file], i+1,
+                      op[file][i].seqnum);
+               list_for_each(&op[file][i].pre, dep, pre_list)
+                       printf("    %s:%u (%u)\n",
+                              filename[dep->prereq.file], dep->prereq.op_num+1,
+                              op[dep->prereq.file][dep->prereq.op_num].seqnum);
+       }
+       check_deps(filename[file], op[file], i);
+}
+
+/* We simply read/write pointers, since we all are children. */
+static bool do_pre(struct tdb_context *tdb,
+                  char *filename[], struct op *op[],
+                  unsigned int file, int pre_fd, unsigned int i,
+                  bool backoff)
+{
+       while (!list_empty(&op[file][i].pre)) {
+               struct depend *dep;
+
+#if DEBUG_DEPS
+               printf("%s:%u:waiting for pre\n", filename[file], i+1);
+               fflush(stdout);
+#endif
+               if (backoff)
+                       alarm(2);
+               else
+                       alarm(10);
+               while (read(pre_fd, &dep, sizeof(dep)) != sizeof(dep)) {
+                       if (errno == EINTR) {
+                               if (backoff) {
+                                       struct op_desc desc = { file,i };
+                                       warnx("%s:%u:avoiding deadlock",
+                                             filename[file], i+1);
+                                       if (write(backoff_fd, &desc,
+                                                 sizeof(desc)) != sizeof(desc))
+                                               err(1, "writing backoff_fd");
+                                       return false;
+                               }
+                               dump_pre(filename, op, file, i);
+                               exit(1);
+                       } else
+                               errx(1, "Reading from pipe");
+               }
+               alarm(0);
+
+#if DEBUG_DEPS
+               printf("%s:%u:got pre %u from %s:%u\n", filename[file], i+1,
+                      dep->needs.op_num+1, filename[dep->prereq.file],
+                      dep->prereq.op_num+1);
+               fflush(stdout);
+#endif
+               /* This could be any op, not just this one. */
+               talloc_free(dep);
+       }
+       return true;
+}
+
+static void do_post(char *filename[], struct op *op[],
+                   unsigned int file, unsigned int i)
+{
+       struct depend *dep;
+
+       list_for_each(&op[file][i].post, dep, post_list) {
+#if DEBUG_DEPS
+               printf("%s:%u:sending to file %s:%u\n", filename[file], i+1,
+                      filename[dep->needs.file], dep->needs.op_num+1);
+#endif
+               if (write(pipes[dep->needs.file].fd[1], &dep, sizeof(dep))
+                   != sizeof(dep))
+                       err(1, "%s:%u failed to tell file %s",
+                           filename[file], i+1, filename[dep->needs.file]);
+       }
+}
+
 static int get_len(TDB_DATA key, TDB_DATA data, void *private_data)
 {
        return data.dsize;
@@ -387,64 +590,53 @@ static int get_len(TDB_DATA key, TDB_DATA data, void *private_data)
 
 static unsigned run_ops(struct tdb_context *tdb,
                        int pre_fd,
-                       const char *filename,
-                       struct op op[],
-                       unsigned int start, unsigned int stop);
+                       char *filename[],
+                       struct op *op[],
+                       unsigned int file,
+                       unsigned int start, unsigned int stop,
+                       bool backoff);
 
 struct traverse_info {
-       struct op *op;
-       const char *filename;
+       struct op **op;
+       char **filename;
+       unsigned file;
        int pre_fd;
        unsigned int start;
        unsigned int i;
 };
 
-/* Trivial case: do whatever they did for this key. */
-static int trivial_traverse(struct tdb_context *tdb,
-                           TDB_DATA key, TDB_DATA data,
-                           void *_tinfo)
-{
-       struct traverse_info *tinfo = _tinfo;
-       struct traverse *trav = tinfo->op[tinfo->start].trav;
-       unsigned int h = hash_key(&key) % (trav->num * 2);
-
-       while (trav->hash[h].index) {
-               if (key_eq(trav->hash[h].key, key)) {
-                       run_ops(tdb, tinfo->pre_fd, tinfo->filename, tinfo->op,
-                               trav->hash[h].index, trav->end);
-                       tinfo->i++;
-                       return 0;
-               }
-               h = (h + 1) % (trav->num * 2);
-       }
-       fail(tinfo->filename, tinfo->start + 1, "unexpected traverse key");
-}
-
 /* More complex.  Just do whatever's they did at the n'th entry. */
 static int nontrivial_traverse(struct tdb_context *tdb,
                               TDB_DATA key, TDB_DATA data,
                               void *_tinfo)
 {
        struct traverse_info *tinfo = _tinfo;
-       struct traverse *trav = tinfo->op[tinfo->start].trav;
+       unsigned int trav_len = tinfo->op[tinfo->file][tinfo->start].group_len;
+       bool avoid_deadlock = false;
 
-       if (tinfo->i == trav->end) {
+       if (tinfo->i == tinfo->start + trav_len) {
                /* This can happen if traverse expects to be empty. */
-               if (tinfo->start + 1 == trav->end)
+               if (trav_len == 1)
                        return 1;
-               fail(tinfo->filename, tinfo->start + 1,
+               fail(tinfo->filename[tinfo->file], tinfo->start + 1,
                     "traverse did not terminate");
        }
 
-       if (tinfo->op[tinfo->i].op != OP_TDB_TRAVERSE)
-               fail(tinfo->filename, tinfo->start + 1,
+       if (tinfo->op[tinfo->file][tinfo->i].type != OP_TDB_TRAVERSE)
+               fail(tinfo->filename[tinfo->file], tinfo->start + 1,
                     "%s:%u:traverse terminated early");
 
+#if TRAVERSALS_TAKE_TRANSACTION_LOCK
+       avoid_deadlock = true;
+#endif
+
        /* Run any normal ops. */
        tinfo->i = run_ops(tdb, tinfo->pre_fd, tinfo->filename, tinfo->op,
-                          tinfo->i+1, trav->end);
+                          tinfo->file, tinfo->i+1, tinfo->start + trav_len,
+                          avoid_deadlock);
 
-       if (tinfo->i == trav->end)
+       /* We backed off, or we hit OP_TDB_TRAVERSE_END/EARLY. */
+       if (tinfo->op[tinfo->file][tinfo->i].type != OP_TDB_TRAVERSE)
                return 1;
 
        return 0;
@@ -452,219 +644,220 @@ static int nontrivial_traverse(struct tdb_context *tdb,
 
 static unsigned op_traverse(struct tdb_context *tdb,
                            int pre_fd,
-                           const char *filename,
+                           char *filename[],
+                           unsigned int file,
                            int (*traversefn)(struct tdb_context *,
                                              tdb_traverse_func, void *),
-                           struct op op[],
+                           struct op *op[],
                            unsigned int start)
 {
-       struct traverse *trav = op[start].trav;
-       struct traverse_info tinfo = { op, filename, pre_fd, start, start+1 };
-
-       /* Trivial case. */
-       if (trav->hash) {
-               int ret = traversefn(tdb, trivial_traverse, &tinfo);
-               if (ret != trav->num)
-                       fail(filename, start+1, "short traversal %i", ret);
-               return trav->end;
-       }
+       struct traverse_info tinfo = { op, filename, file, pre_fd,
+                                      start, start+1 };
 
        traversefn(tdb, nontrivial_traverse, &tinfo);
 
        /* Traversing in wrong order can have strange effects: eg. if
         * original traverse went A (delete A), B, we might do B
         * (delete A).  So if we have ops left over, we do it now. */
-       while (tinfo.i != trav->end) {
-               if (op[tinfo.i].op == OP_TDB_TRAVERSE)
+       while (tinfo.i != start + op[file][start].group_len) {
+               if (op[file][tinfo.i].type == OP_TDB_TRAVERSE
+                   || op[file][tinfo.i].type == OP_TDB_TRAVERSE_END_EARLY)
                        tinfo.i++;
                else
-                       tinfo.i = run_ops(tdb, pre_fd, filename, op,
-                                         tinfo.i, trav->end);
+                       tinfo.i = run_ops(tdb, pre_fd, filename, op, file,
+                                         tinfo.i,
+                                         start + op[file][start].group_len,
+                                         false);
        }
-       return trav->end;
-}
 
-struct depend {
-       /* We can have more than one */
-       struct list_node list;
-       unsigned int file;
-       unsigned int op;
-};
-
-static void do_pre(const char *filename, int pre_fd,
-                  struct op op[], unsigned int i)
-{
-       while (op[i].pre != 0) {
-               unsigned int opnum;
-
-#if DEBUG_DEPS
-               printf("%s:%u:waiting for pre\n", filename, i+1);
-#endif
-               if (read(pre_fd, &opnum, sizeof(opnum)) != sizeof(opnum))
-                       errx(1, "Reading from pipe");
-
-#if DEBUG_DEPS
-               printf("%s:%u:got pre %u\n",
-                      filename, i+1, opnum);
-#endif
-               /* This could be any op, not just this one. */
-               if (op[opnum].pre == 0)
-                       errx(1, "Got unexpected notification for op line %u",
-                            opnum + 1);
-               op[opnum].pre--;
-       }
+       return tinfo.i;
 }
 
-static void do_post(const char *filename, const struct op op[], unsigned int i)
+static void break_out(int sig)
 {
-       struct depend *dep;
-
-       list_for_each(&op[i].post, dep, list) {
-#if DEBUG_DEPS
-               printf("%s:%u:sending %u to file %u\n", filename, i+1,
-                      dep->op, dep->file);
-#endif
-               if (write(pipes[dep->file].fd[1], &dep->op, sizeof(dep->op))
-                   != sizeof(dep->op))
-                       err(1, "Failed to tell file %u", dep->file);
-       }
 }
 
 static __attribute__((noinline))
 unsigned run_ops(struct tdb_context *tdb,
                 int pre_fd,
-                const char *filename,
-                struct op op[], unsigned int start, unsigned int stop)
+                char *filename[],
+                struct op *op[],
+                unsigned int file,
+                unsigned int start, unsigned int stop,
+                bool backoff)
 {
        unsigned int i;
+       struct sigaction sa;
 
+       sa.sa_handler = break_out;
+       sa.sa_flags = 0;
+
+       sigaction(SIGALRM, &sa, NULL);
        for (i = start; i < stop; i++) {
-               do_pre(filename, pre_fd, op, i);
+               if (!do_pre(tdb, filename, op, file, pre_fd, i, backoff))
+                       return i;
 
-               switch (op[i].op) {
+               switch (op[file][i].type) {
                case OP_TDB_LOCKALL:
-                       try(tdb_lockall(tdb), op[i].ret);
+                       try(tdb_lockall(tdb), op[file][i].ret);
                        break;
                case OP_TDB_LOCKALL_MARK:
-                       try(tdb_lockall_mark(tdb), op[i].ret);
+                       try(tdb_lockall_mark(tdb), op[file][i].ret);
                        break;
                case OP_TDB_LOCKALL_UNMARK:
-                       try(tdb_lockall_unmark(tdb), op[i].ret);
+                       try(tdb_lockall_unmark(tdb), op[file][i].ret);
                        break;
                case OP_TDB_LOCKALL_NONBLOCK:
-                       unreliable(tdb_lockall_nonblock(tdb), op[i].ret,
+                       unreliable(tdb_lockall_nonblock(tdb), op[file][i].ret,
                                   tdb_lockall(tdb), tdb_unlockall(tdb));
                        break;
                case OP_TDB_UNLOCKALL:
-                       try(tdb_unlockall(tdb), op[i].ret);
+                       try(tdb_unlockall(tdb), op[file][i].ret);
                        break;
                case OP_TDB_LOCKALL_READ:
-                       try(tdb_lockall_read(tdb), op[i].ret);
+                       try(tdb_lockall_read(tdb), op[file][i].ret);
                        break;
                case OP_TDB_LOCKALL_READ_NONBLOCK:
-                       unreliable(tdb_lockall_read_nonblock(tdb), op[i].ret,
+                       unreliable(tdb_lockall_read_nonblock(tdb),
+                                  op[file][i].ret,
                                   tdb_lockall_read(tdb),
                                   tdb_unlockall_read(tdb));
                        break;
                case OP_TDB_UNLOCKALL_READ:
-                       try(tdb_unlockall_read(tdb), op[i].ret);
+                       try(tdb_unlockall_read(tdb), op[file][i].ret);
                        break;
                case OP_TDB_CHAINLOCK:
-                       try(tdb_chainlock(tdb, op[i].key), op[i].ret);
+                       try(tdb_chainlock(tdb, op[file][i].key),
+                           op[file][i].ret);
                        break;
                case OP_TDB_CHAINLOCK_NONBLOCK:
-                       unreliable(tdb_chainlock_nonblock(tdb, op[i].key),
-                                  op[i].ret,
-                                  tdb_chainlock(tdb, op[i].key),
-                                  tdb_chainunlock(tdb, op[i].key));
+                       unreliable(tdb_chainlock_nonblock(tdb, op[file][i].key),
+                                  op[file][i].ret,
+                                  tdb_chainlock(tdb, op[file][i].key),
+                                  tdb_chainunlock(tdb, op[file][i].key));
                        break;
                case OP_TDB_CHAINLOCK_MARK:
-                       try(tdb_chainlock_mark(tdb, op[i].key), op[i].ret);
+                       try(tdb_chainlock_mark(tdb, op[file][i].key),
+                           op[file][i].ret);
                        break;
                case OP_TDB_CHAINLOCK_UNMARK:
-                       try(tdb_chainlock_unmark(tdb, op[i].key), op[i].ret);
+                       try(tdb_chainlock_unmark(tdb, op[file][i].key),
+                           op[file][i].ret);
                        break;
                case OP_TDB_CHAINUNLOCK:
-                       try(tdb_chainunlock(tdb, op[i].key), op[i].ret);
+                       try(tdb_chainunlock(tdb, op[file][i].key),
+                           op[file][i].ret);
                        break;
                case OP_TDB_CHAINLOCK_READ:
-                       try(tdb_chainlock_read(tdb, op[i].key), op[i].ret);
+                       try(tdb_chainlock_read(tdb, op[file][i].key),
+                           op[file][i].ret);
                        break;
                case OP_TDB_CHAINUNLOCK_READ:
-                       try(tdb_chainunlock_read(tdb, op[i].key), op[i].ret);
-                       break;
-               case OP_TDB_INCREMENT_SEQNUM_NONBLOCK:
-                       tdb_increment_seqnum_nonblock(tdb);
+                       try(tdb_chainunlock_read(tdb, op[file][i].key),
+                           op[file][i].ret);
                        break;
                case OP_TDB_PARSE_RECORD:
-                       try(tdb_parse_record(tdb, op[i].key, get_len, NULL),
-                           op[i].ret);
+                       try(tdb_parse_record(tdb, op[file][i].key, get_len,
+                                            NULL),
+                           op[file][i].ret);
                        break;
                case OP_TDB_EXISTS:
-                       try(tdb_exists(tdb, op[i].key), op[i].ret);
+                       try(tdb_exists(tdb, op[file][i].key), op[file][i].ret);
                        break;
                case OP_TDB_STORE:
-                       try(tdb_store(tdb, op[i].key, op[i].data, op[i].flag),
-                           op[i].ret < 0 ? op[i].ret : 0);
+                       try(tdb_store(tdb, op[file][i].key, op[file][i].data,
+                                     op[file][i].flag),
+                           op[file][i].ret);
                        break;
                case OP_TDB_APPEND:
-                       try(tdb_append(tdb, op[i].key, op[i].data),
-                           op[i].ret < 0 ? op[i].ret : 0);
+                       try(tdb_append(tdb, op[file][i].key, op[file][i].data),
+                           op[file][i].ret);
                        break;
                case OP_TDB_GET_SEQNUM:
-                       try(tdb_get_seqnum(tdb), op[i].ret);
+                       try(tdb_get_seqnum(tdb), op[file][i].ret);
                        break;
                case OP_TDB_WIPE_ALL:
-                       try(tdb_wipe_all(tdb), op[i].ret);
+                       try(tdb_wipe_all(tdb), op[file][i].ret);
                        break;
                case OP_TDB_TRANSACTION_START:
-                       try(tdb_transaction_start(tdb), op[i].ret);
+                       try(tdb_transaction_start(tdb), op[file][i].ret);
                        break;
                case OP_TDB_TRANSACTION_CANCEL:
-                       try(tdb_transaction_cancel(tdb), op[i].ret);
+                       try(tdb_transaction_cancel(tdb), op[file][i].ret);
+                       break;
+               case OP_TDB_TRANSACTION_PREPARE_COMMIT:
+                       try(tdb_transaction_prepare_commit(tdb),
+                           op[file][i].ret);
                        break;
                case OP_TDB_TRANSACTION_COMMIT:
-                       try(tdb_transaction_commit(tdb), op[i].ret);
+                       try(tdb_transaction_commit(tdb), op[file][i].ret);
                        break;
                case OP_TDB_TRAVERSE_READ_START:
-                       i = op_traverse(tdb, pre_fd, filename,
+                       i = op_traverse(tdb, pre_fd, filename, file,
                                        tdb_traverse_read, op, i);
                        break;
                case OP_TDB_TRAVERSE_START:
-                       i = op_traverse(tdb, pre_fd, filename,
+                       i = op_traverse(tdb, pre_fd, filename, file,
                                        tdb_traverse, op, i);
                        break;
                case OP_TDB_TRAVERSE:
+               case OP_TDB_TRAVERSE_END_EARLY:
                        /* Terminate: we're in a traverse, and we've
                         * done our ops. */
                        return i;
                case OP_TDB_TRAVERSE_END:
-                       fail(filename, i+1, "unepxected end traverse");
+                       fail(filename[file], i+1, "unexpected end traverse");
                /* FIXME: These must be treated like traverse. */
                case OP_TDB_FIRSTKEY:
-                       if (!key_eq(tdb_firstkey(tdb), op[i].data))
-                               fail(filename, i+1, "bad firstkey");
+                       if (!key_eq(tdb_firstkey(tdb), op[file][i].data))
+                               fail(filename[file], i+1, "bad firstkey");
                        break;
                case OP_TDB_NEXTKEY:
-                       if (!key_eq(tdb_nextkey(tdb, op[i].key), op[i].data))
-                               fail(filename, i+1, "bad nextkey");
+                       if (!key_eq(tdb_nextkey(tdb, op[file][i].key),
+                                   op[file][i].data))
+                               fail(filename[file], i+1, "bad nextkey");
                        break;
                case OP_TDB_FETCH: {
-                       TDB_DATA f = tdb_fetch(tdb, op[i].key);
-                       if (!key_eq(f, op[i].data))
-                               fail(filename, i+1, "bad fetch %u", f.dsize);
+                       TDB_DATA f = tdb_fetch(tdb, op[file][i].key);
+                       if (!key_eq(f, op[file][i].data))
+                               fail(filename[file], i+1, "bad fetch %u",
+                                    f.dsize);
                        break;
                }
                case OP_TDB_DELETE:
-                       try(tdb_delete(tdb, op[i].key), op[i].ret);
+                       try(tdb_delete(tdb, op[file][i].key), op[file][i].ret);
+                       break;
+               case OP_TDB_REPACK:
+                       /* We do nothing here: the transaction and traverse are
+                        * traced.  It's in the trace to mark it, since it
+                        * may become unnecessary in future. */
                        break;
                }
-               do_post(filename, op, i);
+               do_post(filename, op, file, i);
        }
        return i;
 }
 
-static struct op *load_tracefile(const char *filename, unsigned int *num,
+/* tdbtorture, in particular, can do a tdb_close with a transaction in
+ * progress. */
+static struct op *maybe_cancel_transaction(char *filename[], unsigned int file,
+                                          struct op *op, unsigned int *num)
+{
+       unsigned int start = op_find_start(op, *num, OP_TDB_TRANSACTION_START);
+
+       if (start) {
+               char *words[] = { "<unknown>", "tdb_close", NULL };
+               add_op(filename[file], &op, *num, op[start].seqnum,
+                      OP_TDB_TRANSACTION_CANCEL);
+               op_analyze_transaction(filename, op, file, *num, words);
+               (*num)++;
+       }
+       return op;
+}
+
+static struct op *load_tracefile(char *filename[],
+                                unsigned int file,
+                                unsigned int *num,
                                 unsigned int *hashsize,
                                 unsigned int *tdb_flags,
                                 unsigned int *open_flags)
@@ -673,19 +866,19 @@ static struct op *load_tracefile(const char *filename, unsigned int *num,
        struct op *op = talloc_array(NULL, struct op, 1);
        char **words;
        char **lines;
-       char *file;
+       char *contents;
 
-       file = grab_file(NULL, filename, NULL);
-       if (!file)
-               err(1, "Reading %s", filename);
+       contents = grab_file(NULL, filename[file], NULL);
+       if (!contents)
+               err(1, "Reading %s", filename[file]);
 
-       lines = strsplit(file, file, "\n", NULL);
+       lines = strsplit(contents, contents, "\n", NULL);
        if (!lines[0])
-               errx(1, "%s is empty", filename);
+               errx(1, "%s is empty", filename[file]);
 
        words = strsplit(lines, lines[0], " ", NULL);
        if (!streq(words[1], "tdb_open"))
-               fail(filename, 1, "does not start with tdb_open");
+               fail(filename[file], 1, "does not start with tdb_open");
 
        *hashsize = atoi(words[2]);
        *tdb_flags = strtoul(words[3], NULL, 0);
@@ -696,54 +889,250 @@ static struct op *load_tracefile(const char *filename, unsigned int *num,
 
                words = strsplit(lines, lines[i], " ", NULL);
                if (!words[0] || !words[1])
-                       fail(filename, i+1, "Expected serial number and op");
+                       fail(filename[file], i+1,
+                            "Expected seqnum number and op");
               
                opt = find_keyword(words[1], strlen(words[1]));
                if (!opt) {
                        if (streq(words[1], "tdb_close")) {
                                if (lines[i+1])
-                                       fail(filename, i+2,
+                                       fail(filename[file], i+2,
                                             "lines after tdb_close");
                                *num = i;
                                talloc_free(lines);
-                               return op;
+                               return maybe_cancel_transaction(filename, file,
+                                                               op, num);
                        }
-                       fail(filename, i+1, "Unknown operation '%s'", words[1]);
+                       fail(filename[file], i+1,
+                            "Unknown operation '%s'", words[1]);
                }
 
-               add_op(filename, &op, i, atoi(words[0]), opt->type);
-               opt->enhance_op(filename, op, i, words);
+               add_op(filename[file], &op, i, atoi(words[0]), opt->type);
+               opt->enhance_op(filename, op, file, i, words);
        }
 
-       fprintf(stderr, "%s:%u:last operation is not tdb_close: incomplete?",
-             filename, i);
-       talloc_free(lines);
+       if (!quiet)
+               fprintf(stderr,
+                       "%s:%u:last operation is not tdb_close: incomplete?",
+                       filename[file], i);
+
+       talloc_free(contents);
        *num = i - 1;
-       return op;
+       return maybe_cancel_transaction(filename, file, op, num);
 }
 
 /* We remember all the keys we've ever seen, and who has them. */
-struct key_user {
-       unsigned int file;
-       unsigned int op_num;
-};
-
 struct keyinfo {
        TDB_DATA key;
        unsigned int num_users;
-       struct key_user *user;
+       struct op_desc *user;
 };
 
-static bool changes_db(const struct op *op)
+static bool starts_transaction(const struct op *op)
 {
-       if (op->ret != 0)
-               return false;
+       return op->type == OP_TDB_TRANSACTION_START;
+}
 
-       return op->op == OP_TDB_STORE
-               || op->op == OP_TDB_APPEND
-               || op->op == OP_TDB_WIPE_ALL
-               || op->op == OP_TDB_TRANSACTION_COMMIT
-               || op->op == OP_TDB_DELETE;
+static bool in_transaction(const struct op op[], unsigned int i)
+{
+       return op[i].group_start && starts_transaction(&op[op[i].group_start]);
+}
+
+static bool successful_transaction(const struct op *op)
+{
+       return starts_transaction(op)
+               && op[op->group_len].type == OP_TDB_TRANSACTION_COMMIT;
+}
+
+static bool starts_traverse(const struct op *op)
+{
+       return op->type == OP_TDB_TRAVERSE_START
+               || op->type == OP_TDB_TRAVERSE_READ_START;
+}
+
+static bool in_traverse(const struct op op[], unsigned int i)
+{
+       return op[i].group_start && starts_traverse(&op[op[i].group_start]);
+}
+
+static bool starts_chainlock(const struct op *op)
+{
+       return op->type == OP_TDB_CHAINLOCK_READ
+               || op->type == OP_TDB_CHAINLOCK;
+}
+
+static bool in_chainlock(const struct op op[], unsigned int i)
+{
+       return op[i].group_start && starts_chainlock(&op[op[i].group_start]);
+}
+
+static const TDB_DATA must_not_exist;
+static const TDB_DATA must_exist;
+static const TDB_DATA not_exists_or_empty;
+
+/* NULL means doesn't care if it exists or not, &must_exist means
+ * it must exist but we don't care what, &must_not_exist means it must
+ * not exist, otherwise the data it needs. */
+static const TDB_DATA *needs(const TDB_DATA *key, const struct op *op)
+{
+       /* Look through for an op in this transaction which needs this key. */
+       if (starts_transaction(op) || starts_chainlock(op)) {
+               unsigned int i;
+               const TDB_DATA *need = NULL;
+
+               for (i = 1; i < op->group_len; i++) {
+                       if (key_eq(op[i].key, *key)
+                           || op[i].type == OP_TDB_WIPE_ALL) {
+                               need = needs(key, &op[i]);
+                               /* tdb_exists() is special: there might be
+                                * something in the transaction with more
+                                * specific requirements.  Other ops don't have
+                                * specific requirements (eg. store or delete),
+                                * but they change the value so we can't get
+                                * more information from future ops. */
+                               if (op[i].type != OP_TDB_EXISTS)
+                                       break;
+                       }
+               }
+
+               return need;
+       }
+
+       switch (op->type) {
+       /* FIXME: Pull forward deps, since we can deadlock */
+       case OP_TDB_CHAINLOCK:
+       case OP_TDB_CHAINLOCK_NONBLOCK:
+       case OP_TDB_CHAINLOCK_MARK:
+       case OP_TDB_CHAINLOCK_UNMARK:
+       case OP_TDB_CHAINUNLOCK:
+       case OP_TDB_CHAINLOCK_READ:
+       case OP_TDB_CHAINUNLOCK_READ:
+               return NULL;
+
+       case OP_TDB_APPEND:
+               if (op->append.pre.dsize == 0)
+                       return &not_exists_or_empty;
+               return &op->append.pre;
+
+       case OP_TDB_STORE:
+               if (op->flag == TDB_INSERT) {
+                       if (op->ret < 0)
+                               return &must_exist;
+                       else
+                               return &must_not_exist;
+               } else if (op->flag == TDB_MODIFY) {
+                       if (op->ret < 0)
+                               return &must_not_exist;
+                       else
+                               return &must_exist;
+               }
+               /* No flags?  Don't care */
+               return NULL;
+
+       case OP_TDB_EXISTS:
+               if (op->ret == 1)
+                       return &must_exist;
+               else
+                       return &must_not_exist;
+
+       case OP_TDB_PARSE_RECORD:
+               if (op->ret < 0)
+                       return &must_not_exist;
+               return &must_exist;
+
+       /* FIXME: handle these. */
+       case OP_TDB_WIPE_ALL:
+       case OP_TDB_FIRSTKEY:
+       case OP_TDB_NEXTKEY:
+       case OP_TDB_GET_SEQNUM:
+       case OP_TDB_TRAVERSE:
+       case OP_TDB_TRANSACTION_COMMIT:
+       case OP_TDB_TRANSACTION_CANCEL:
+       case OP_TDB_TRANSACTION_START:
+               return NULL;
+
+       case OP_TDB_FETCH:
+               if (!op->data.dptr)
+                       return &must_not_exist;
+               return &op->data;
+
+       case OP_TDB_DELETE:
+               if (op->ret < 0)
+                       return &must_not_exist;
+               return &must_exist;
+
+       default:
+               errx(1, "Unexpected op type %i", op->type);
+       }
+       
+}
+
+/* What's the data after this op?  pre if nothing changed. */
+static const TDB_DATA *gives(const TDB_DATA *key, const TDB_DATA *pre,
+                            const struct op *op)
+{
+       if (starts_transaction(op) || starts_chainlock(op)) {
+               unsigned int i;
+
+               /* Cancelled transactions don't change anything. */
+               if (op[op->group_len].type == OP_TDB_TRANSACTION_CANCEL)
+                       return pre;
+               assert(op[op->group_len].type == OP_TDB_TRANSACTION_COMMIT
+                      || op[op->group_len].type == OP_TDB_CHAINUNLOCK_READ
+                      || op[op->group_len].type == OP_TDB_CHAINUNLOCK);
+
+               for (i = 1; i < op->group_len; i++) {
+                       /* This skips nested transactions, too */
+                       if (key_eq(op[i].key, *key)
+                           || op[i].type == OP_TDB_WIPE_ALL)
+                               pre = gives(key, pre, &op[i]);
+               }
+               return pre;
+       }
+
+       /* Failed ops don't change state of db. */
+       if (op->ret < 0)
+               return pre;
+
+       if (op->type == OP_TDB_DELETE || op->type == OP_TDB_WIPE_ALL)
+               return &tdb_null;
+
+       if (op->type == OP_TDB_APPEND)
+               return &op->append.post;
+
+       if (op->type == OP_TDB_STORE)
+               return &op->data;
+
+       return pre;
+}
+
+static void add_hash_user(struct keyinfo *hash,
+                         unsigned int h,
+                         struct op *op[],
+                         unsigned int file,
+                         unsigned int op_num)
+{
+       hash[h].user = talloc_realloc(hash, hash[h].user,
+                                     struct op_desc, hash[h].num_users+1);
+
+       /* If it's in a transaction, it's the transaction which
+        * matters from an analysis POV. */
+       if (in_transaction(op[file], op_num)
+           || in_chainlock(op[file], op_num)) {
+               unsigned i;
+
+               op_num = op[file][op_num].group_start;
+
+               /* Don't include twice. */
+               for (i = 0; i < hash[h].num_users; i++) {
+                       if (hash[h].user[i].file == file
+                           && hash[h].user[i].op_num == op_num)
+                               return;
+               }
+       }
+       hash[h].user[hash[h].num_users].op_num = op_num;
+       hash[h].user[hash[h].num_users].file = file;
+       hash[h].num_users++;
 }
 
 static struct keyinfo *hash_ops(struct op *op[], unsigned int num_ops[],
@@ -752,39 +1141,16 @@ static struct keyinfo *hash_ops(struct op *op[], unsigned int num_ops[],
        unsigned int i, j, h;
        struct keyinfo *hash;
 
-       /* Gcc nexted function extension.  How cool is this? */
-       int compare_user_serial(const void *_a, const void *_b)
-       {
-               const struct key_user *a = _a, *b = _b;
-               int ret = op[a->file][a->op_num].serial
-                       - op[b->file][b->op_num].serial;
-
-               /* Fetches don't inc serial, so we put changes first. */
-               if (ret == 0) {
-                       if (changes_db(&op[a->file][a->op_num])
-                           && !changes_db(&op[b->file][b->op_num]))
-                               return -1;
-                       if (changes_db(&op[b->file][b->op_num])
-                           && !changes_db(&op[a->file][a->op_num]))
-                               return 1;
-               }
-               return ret;
-       }
-
        hash = talloc_zero_array(op[0], struct keyinfo, total_keys*2);
        for (i = 0; i < num; i++) {
                for (j = 1; j < num_ops[i]; j++) {
                        /* We can't do this on allocation, due to realloc. */
                        list_head_init(&op[i][j].post);
+                       list_head_init(&op[i][j].pre);
 
                        if (!op[i][j].key.dptr)
                                continue;
 
-                       /* We don't wait for traverse keys */
-                       /* FIXME: We should, for trivial traversals. */
-                       if (op[i][j].op == OP_TDB_TRAVERSE)
-                               continue;
-
                        h = hash_key(&op[i][j].key) % (total_keys * 2);
                        while (!key_eq(hash[h].key, op[i][j].key)) {
                                if (!hash[h].key.dptr) {
@@ -798,129 +1164,623 @@ static struct keyinfo *hash_ops(struct op *op[], unsigned int num_ops[],
                                talloc_free(op[i][j].key.dptr);
                                op[i][j].key.dptr = hash[h].key.dptr;
                        }
-                       hash[h].user = talloc_realloc(hash, hash[h].user,
-                                                    struct key_user,
-                                                    hash[h].num_users+1);
-                       hash[h].user[hash[h].num_users].op_num = j;
-                       hash[h].user[hash[h].num_users].file = i;
-                       hash[h].num_users++;
+
+                       add_hash_user(hash, h, op, i, j);
                }
        }
 
-       /* Now sort into seqnum order. */
-       for (h = 0; h < total_keys * 2; h++)
-               qsort(hash[h].user, hash[h].num_users, sizeof(hash[h].user[0]),
-                     compare_user_serial);
+       /* Any wipe all entries need adding to all hash entries. */
+       for (h = 0; h < total_keys*2; h++) {
+               if (!hash[h].num_users)
+                       continue;
+
+               for (i = 0; i < num_wipe_alls; i++)
+                       add_hash_user(hash, h, op,
+                                     wipe_alls[i].file, wipe_alls[i].op_num);
+       }
 
        return hash;
 }
 
-static void add_dependency(void *ctx,
-                          struct op *op[],
-                          unsigned int needs_file,
-                          unsigned int needs_opnum,
-                          unsigned int satisfies_file,
-                          unsigned int satisfies_opnum)
+static bool satisfies(const TDB_DATA *key, const TDB_DATA *data,
+                     const struct op *op)
 {
-       struct depend *post;
+       const TDB_DATA *need = needs(key, op);
+
+       /* Don't need anything?  Cool. */
+       if (!need)
+               return true;
+
+       /* This should be tdb_null or a real value. */
+       assert(data != &must_exist);
+       assert(data != &must_not_exist);
+       assert(data != &not_exists_or_empty);
+
+       /* Must not exist?  data must not exist. */
+       if (need == &must_not_exist)
+               return data == &tdb_null;
 
-       post = talloc(ctx, struct depend);
-       post->file = needs_file;
-       post->op = needs_opnum;
-       list_add(&op[satisfies_file][satisfies_opnum].post, &post->list);
+       /* Must exist? */
+       if (need == &must_exist)
+               return data != &tdb_null;
 
-       op[needs_file][needs_opnum].pre++;
+       /* Either noexist or empty. */
+       if (need == &not_exists_or_empty)
+               return data->dsize == 0;
+
+       /* Needs something specific. */
+       return key_eq(*data, *need);
 }
 
-static void derive_dependencies(char *filename[],
-                               struct op *op[], unsigned int num_ops[],
-                               unsigned int num)
+static void move_to_front(struct op_desc res[], unsigned off, unsigned elem)
 {
-       struct keyinfo *hash;
+       if (elem != off) {
+               struct op_desc tmp = res[elem];
+               memmove(res + off + 1, res + off, (elem - off)*sizeof(res[0]));
+               res[off] = tmp;
+       }
+}
+
+static void restore_to_pos(struct op_desc res[], unsigned off, unsigned elem)
+{
+       if (elem != off) {
+               struct op_desc tmp = res[off];
+               memmove(res + off, res + off + 1, (elem - off)*sizeof(res[0]));
+               res[elem] = tmp;
+       }
+}
+
+static bool sort_deps(char *filename[], struct op *op[],
+                     struct op_desc res[],
+                     unsigned off, unsigned num,
+                     const TDB_DATA *key, const TDB_DATA *data,
+                     unsigned num_files, unsigned fuzz)
+{
+       unsigned int i, files_done;
+       struct op *this_op;
+       bool done[num_files];
+
+       /* None left?  We're sorted. */
+       if (off == num)
+               return true;
+
+       /* Does this make sequence number go backwards?  Allow a little fuzz. */
+       if (off > 0) {
+               int seqnum1 = op[res[off-1].file][res[off-1].op_num].seqnum;
+               int seqnum2 = op[res[off].file][res[off].op_num].seqnum;
+
+               if (seqnum1 - seqnum2 > (int)fuzz) {
+#if DEBUG_DEPS
+                       printf("Seqnum jump too far (%u -> %u)\n",
+                              seqnum1, seqnum2);
+#endif
+                       return false;
+               }
+       }
+
+       memset(done, 0, sizeof(done));
+
+       /* Since ops within a trace file are ordered, we just need to figure
+        * out which file to try next.  Since we don't take into account
+        * inter-key relationships (which exist by virtue of trace file order),
+        * we minimize the chance of harm by trying to keep in seqnum order. */
+       for (files_done = 0, i = off; i < num && files_done < num_files; i++) {
+               if (done[res[i].file])
+                       continue;
+
+               this_op = &op[res[i].file][res[i].op_num];
+
+               /* Is what we have good enough for this op? */
+               if (satisfies(key, data, this_op)) {
+                       move_to_front(res, off, i);
+                       if (sort_deps(filename, op, res, off+1, num,
+                                     key, gives(key, data, this_op),
+                                     num_files, fuzz))
+                               return true;
+                       restore_to_pos(res, off, i);
+               }
+               done[res[i].file] = true;
+               files_done++;
+       }
+
+       /* No combination worked. */
+       return false;
+}
+
+static void check_dep_sorting(struct op_desc user[], unsigned num_users,
+                             unsigned num_files)
+{
+#if DEBUG_DEPS
        unsigned int i;
+       unsigned minima[num_files];
 
-       /* Create hash table for faster key lookup. */
-       hash = hash_ops(op, num_ops, num);
+       memset(minima, 0, sizeof(minima));
+       for (i = 0; i < num_users; i++) {
+               assert(minima[user[i].file] < user[i].op_num);
+               minima[user[i].file] = user[i].op_num;
+       }
+#endif
+}
 
-       /* We make the naive assumption that two ops on the same key
-        * have to be ordered; it's overkill. */
-       for (i = 0; i < total_keys * 2; i++) {
-               unsigned int j;
+/* All these ops happen on the same key.  Which comes first?
+ *
+ * This can happen both because read ops or failed write ops don't
+ * change sequence number, and also due to race since we access the
+ * number unlocked (the race can cause less detectable ordering problems,
+ * in which case we'll deadlock and report: fix manually in that case).
+ */
+static bool figure_deps(char *filename[], struct op *op[],
+                       const TDB_DATA *key, const TDB_DATA *data,
+                       struct op_desc user[],
+                       unsigned num_users, unsigned num_files)
+{
+       unsigned int fuzz;
+
+       /* We prefer to keep strict seqnum order if possible: it's the
+        * most likely.  We get more lax if that fails. */
+       for (fuzz = 0; fuzz < 100; fuzz = (fuzz + 1)*2) {
+               if (sort_deps(filename, op, user, 0, num_users, key, data,
+                             num_files, fuzz))
+                       break;
+       }
+
+       if (fuzz >= 100)
+               return false;
+
+       check_dep_sorting(user, num_users, num_files);
+       return true;
+}
+
+/* We're having trouble sorting out dependencies for this key.  Assume that it's
+ * a pre-existing record in the db, so determine a likely value. */
+static const TDB_DATA *preexisting_data(char *filename[], struct op *op[],
+                                       const TDB_DATA *key,
+                                       struct op_desc *user,
+                                       unsigned int num_users)
+{
+       unsigned int i;
+       const TDB_DATA *data;
+
+       for (i = 0; i < num_users; i++) {
+               data = needs(key, &op[user->file][user->op_num]);
+               if (data && data != &must_not_exist) {
+                       if (!quiet)
+                               printf("%s:%u: needs pre-existing record\n",
+                                      filename[user->file], user->op_num+1);
+                       return data;
+               }
+       }
+       return &tdb_null;
+}
+
+static void sort_ops(struct tdb_context *tdb,
+                    struct keyinfo hash[], char *filename[], struct op *op[],
+                    unsigned int num)
+{
+       unsigned int h;
+
+       /* Gcc nexted function extension.  How cool is this? */
+       int compare_seqnum(const void *_a, const void *_b)
+       {
+               const struct op_desc *a = _a, *b = _b;
+
+               /* First, maintain order within any trace file. */
+               if (a->file == b->file)
+                       return a->op_num - b->op_num;
+
+               /* Otherwise, arrange by seqnum order. */
+               if (op[a->file][a->op_num].seqnum !=
+                   op[b->file][b->op_num].seqnum)
+                       return op[a->file][a->op_num].seqnum
+                               - op[b->file][b->op_num].seqnum;
+
+               /* Cancelled transactions are assumed to happen first. */
+               if (starts_transaction(&op[a->file][a->op_num])
+                   && !successful_transaction(&op[a->file][a->op_num]))
+                       return -1;
+               if (starts_transaction(&op[b->file][b->op_num])
+                   && !successful_transaction(&op[b->file][b->op_num]))
+                       return 1;
+
+               /* No idea. */
+               return 0;
+       }
+
+       /* Now sort into seqnum order. */
+       for (h = 0; h < total_keys * 2; h++) {
+               struct op_desc *user = hash[h].user;
+
+               qsort(user, hash[h].num_users, sizeof(user[0]), compare_seqnum);
+               if (!figure_deps(filename, op, &hash[h].key, &tdb_null, user,
+                                hash[h].num_users, num)) {
+                       const TDB_DATA *data;
+
+                       data = preexisting_data(filename, op, &hash[h].key,
+                                               user, hash[h].num_users);
+                       /* Give the first op what it wants: does that help? */
+                       if (!figure_deps(filename, op, &hash[h].key, data, user,
+                                        hash[h].num_users, num))
+                               fail(filename[user[0].file], user[0].op_num+1,
+                                    "Could not resolve inter-dependencies");
+                       if (tdb_store(tdb, hash[h].key, *data, TDB_INSERT) != 0)
+                               errx(1, "Could not store initial value");
+               }
+       }
+}
+
+static int destroy_depend(struct depend *dep)
+{
+       list_del(&dep->pre_list);
+       list_del(&dep->post_list);
+       return 0;
+}
+
+static void add_dependency(void *ctx,
+                          struct op *op[],
+                          char *filename[],
+                          const struct op_desc *needs,
+                          const struct op_desc *prereq)
+{
+       struct depend *dep;
+
+       /* We don't depend on ourselves. */
+       if (needs->file == prereq->file) {
+               assert(prereq->op_num < needs->op_num);
+               return;
+       }
 
-               for (j = 1; j < hash[i].num_users; j++) {
-                       /* We don't depend on ourselves. */
-                       if (hash[i].user[j].file == hash[i].user[j-1].file)
-                               continue;
 #if DEBUG_DEPS
-                       printf("%s:%u: depends on %s:%u\n",
-                              filename[hash[i].user[j].file],
-                              hash[i].user[j].op_num+1,
-                              filename[hash[i].user[j-1].file],
-                              hash[i].user[j-1].op_num+1);
+       printf("%s:%u: depends on %s:%u\n",
+              filename[needs->file], needs->op_num+1,
+              filename[prereq->file], prereq->op_num+1);
 #endif
-                       add_dependency(hash, op,
-                                      hash[i].user[j].file,
-                                      hash[i].user[j].op_num,
-                                      hash[i].user[j-1].file,
-                                      hash[i].user[j-1].op_num);
+
+       dep = talloc(ctx, struct depend);
+       dep->needs = *needs;
+       dep->prereq = *prereq;
+
+#if TRAVERSALS_TAKE_TRANSACTION_LOCK
+       /* If something in a traverse depends on something in another
+        * traverse/transaction, it creates a dependency between the
+        * two groups. */
+       if ((in_traverse(op[prereq->file], prereq->op_num)
+            && (starts_transaction(&op[needs->file][needs->op_num])
+                || starts_traverse(&op[needs->file][needs->op_num])))
+           || (in_traverse(op[needs->file], needs->op_num)
+               && (starts_transaction(&op[prereq->file][prereq->op_num])
+                   || starts_traverse(&op[prereq->file][prereq->op_num])))) {
+               unsigned int start;
+
+               /* We are satisfied by end of group. */
+               start = op[prereq->file][prereq->op_num].group_start;
+               dep->prereq.op_num = start + op[prereq->file][start].group_len;
+               /* And we need that done by start of our group. */
+               dep->needs.op_num = op[needs->file][needs->op_num].group_start;
+       }
+
+       /* There is also this case:
+        *  <traverse> <read foo> ...
+        *  <transaction> ... </transaction> <create foo>
+        * Where if we start the traverse then wait, we could block
+        * the transaction and deadlock.
+        *
+        * We try to address this by ensuring that where seqnum indicates it's
+        * possible, we wait for <create foo> before *starting* traverse.
+        */
+       else if (in_traverse(op[needs->file], needs->op_num)) {
+               struct op *need = &op[needs->file][needs->op_num];
+               if (op[needs->file][need->group_start].seqnum >
+                   op[prereq->file][prereq->op_num].seqnum) {
+                       dep->needs.op_num = need->group_start;
                }
        }
+#endif
+
+       /* If you depend on a transaction or chainlock, you actually
+        * depend on it ending. */
+       if (starts_transaction(&op[prereq->file][dep->prereq.op_num])
+           || starts_chainlock(&op[prereq->file][dep->prereq.op_num])) {
+               dep->prereq.op_num
+                       += op[dep->prereq.file][dep->prereq.op_num].group_len;
+#if DEBUG_DEPS
+               printf("-> Actually end of transaction %s:%u\n",
+                      filename[dep->prereq->file], dep->prereq->op_num+1);
+#endif
+       } else
+               /* We should never create a dependency from middle of
+                * a transaction. */
+               assert(!in_transaction(op[prereq->file], dep->prereq.op_num)
+                      || op[prereq->file][dep->prereq.op_num].type
+                      == OP_TDB_TRANSACTION_COMMIT
+                      || op[prereq->file][dep->prereq.op_num].type
+                      == OP_TDB_TRANSACTION_CANCEL);
+
+       list_add(&op[dep->prereq.file][dep->prereq.op_num].post,
+                &dep->post_list);
+       list_add(&op[dep->needs.file][dep->needs.op_num].pre,
+                &dep->pre_list);
+       talloc_set_destructor(dep, destroy_depend);
 }
 
-int main(int argc, char *argv[])
+static bool changes_db(const TDB_DATA *key, const struct op *op)
 {
-       struct timeval start, end;
-       unsigned int i, num_ops[argc], hashsize[argc], tdb_flags[argc], open_flags[argc];
-       struct op *op[argc];
-       int fds[2];
-       char c;
+       return gives(key, NULL, op) != NULL;
+}
 
-       if (argc < 3)
-               errx(1, "Usage: %s <tdbfile> <tracefile>...", argv[0]);
+static void depend_on_previous(struct op *op[],
+                              char *filename[],
+                              unsigned int num,
+                              struct op_desc user[],
+                              unsigned int i,
+                              int prev)
+{
+       bool deps[num];
+       int j;
 
-       pipes = talloc_array(NULL, struct pipe, argc - 2);
-       for (i = 0; i < argc - 2; i++) {
-               op[i] = load_tracefile(argv[2+i], &num_ops[i], &hashsize[i],
-                                      &tdb_flags[i], &open_flags[i]);
-               if (pipe(pipes[i].fd) != 0)
-                       err(1, "creating pipe");
+       if (i == 0)
+               return;
+
+       if (prev == i - 1) {
+               /* Just depend on previous. */
+               add_dependency(NULL, op, filename, &user[i], &user[prev]);
+               return;
        }
 
-       derive_dependencies(argv+2, op, num_ops, i);
+       /* We have to wait for the readers.  Find last one in *each* file. */
+       memset(deps, 0, sizeof(deps));
+       deps[user[i].file] = true;
+       for (j = i - 1; j > prev; j--) {
+               if (!deps[user[j].file]) {
+                       add_dependency(NULL, op, filename, &user[i], &user[j]);
+                       deps[user[j].file] = true;
+               }
+       }
+}
 
-       /* Don't fork for single arg case: simple debugging. */
-       if (argc == 3) {
-               struct tdb_context *tdb;
-               tdb = tdb_open_ex(argv[1], hashsize[0], tdb_flags[0],
-                                 open_flags[0], 0600,
-                                 NULL, hash_key);
-               run_ops(tdb, pipes[0].fd[0], argv[2],
-                       op[0], 1, num_ops[0]);
-               exit(0);
+/* This is simple, but not complete.  We don't take into account
+ * indirect dependencies. */
+static void optimize_dependencies(struct op *op[], unsigned int num_ops[],
+                                 unsigned int num)
+{
+       unsigned int i, j;
+
+       /* There can only be one real dependency on each file */
+       for (i = 0; i < num; i++) {
+               for (j = 1; j < num_ops[i]; j++) {
+                       struct depend *dep, *next;
+                       struct depend *prev[num];
+
+                       memset(prev, 0, sizeof(prev));
+
+                       list_for_each_safe(&op[i][j].pre, dep, next, pre_list) {
+                               if (!prev[dep->prereq.file]) {
+                                       prev[dep->prereq.file] = dep;
+                                       continue;
+                               }
+                               if (prev[dep->prereq.file]->prereq.op_num
+                                   < dep->prereq.op_num) {
+                                       talloc_free(prev[dep->prereq.file]);
+                                       prev[dep->prereq.file] = dep;
+                               } else
+                                       talloc_free(dep);
+                       }
+               }
        }
 
-       if (pipe(fds) != 0)
-               err(1, "creating pipe");
+       for (i = 0; i < num; i++) {
+               int deps[num];
 
-       for (i = 0; i < argc - 2; i++) {
+               for (j = 0; j < num; j++)
+                       deps[j] = -1;
+
+               for (j = 1; j < num_ops[i]; j++) {
+                       struct depend *dep, *next;
+
+                       list_for_each_safe(&op[i][j].pre, dep, next, pre_list) {
+                               if (deps[dep->prereq.file]
+                                   >= (int)dep->prereq.op_num)
+                                       talloc_free(dep);
+                               else
+                                       deps[dep->prereq.file]
+                                               = dep->prereq.op_num;
+                       }
+               }
+       }
+}
+
+#if TRAVERSALS_TAKE_TRANSACTION_LOCK
+/* Force an order among the traversals, so they don't deadlock (as much) */
+static void make_traverse_depends(char *filename[],
+                                 struct op *op[], unsigned int num_ops[],
+                                 unsigned int num)
+{
+       unsigned int i, num_traversals = 0;
+       int j;
+       struct op_desc *desc;
+
+       /* Sort by which one runs first. */
+       int compare_traverse_desc(const void *_a, const void *_b)
+       {
+               const struct op_desc *da = _a, *db = _b;
+               const struct op *a = &op[da->file][da->op_num],
+                       *b = &op[db->file][db->op_num];
+
+               if (a->seqnum != b->seqnum)
+                       return a->seqnum - b->seqnum;
+
+               /* If they have same seqnum, it means one didn't make any
+                * changes.  Thus sort by end in that case. */
+               return a[a->group_len].seqnum - b[b->group_len].seqnum;
+       }
+
+       desc = talloc_array(NULL, struct op_desc, 1);
+
+       /* Count them. */
+       for (i = 0; i < num; i++) {
+               for (j = 1; j < num_ops[i]; j++) {
+                       /* Traverse start (ignore those in
+                        * transactions; they're already covered by
+                        * transaction dependencies). */
+                       if (starts_traverse(&op[i][j])
+                           && !in_transaction(op[i], j)) {
+                               desc = talloc_realloc(NULL, desc,
+                                                     struct op_desc,
+                                                     num_traversals+1);
+                               desc[num_traversals].file = i;
+                               desc[num_traversals].op_num = j;
+                               num_traversals++;
+                       }
+               }
+       }
+       qsort(desc, num_traversals, sizeof(desc[0]), compare_traverse_desc);
+
+       for (i = 1; i < num_traversals; i++) {
+               const struct op *prev = &op[desc[i-1].file][desc[i-1].op_num];
+               const struct op *curr = &op[desc[i].file][desc[i].op_num];
+
+               /* Read traverses don't depend on each other (read lock). */
+               if (prev->type == OP_TDB_TRAVERSE_READ_START
+                   && curr->type == OP_TDB_TRAVERSE_READ_START)
+                       continue;
+
+               /* Only make dependency if it's clear. */
+               if (compare_traverse_desc(&desc[i], &desc[i-1])) {
+                       /* i depends on end of traverse i-1. */
+                       struct op_desc end = desc[i-1];
+                       end.op_num += prev->group_len;
+                       add_dependency(NULL, op, filename, &desc[i], &end);
+               }
+       }
+       talloc_free(desc);
+}
+
+static void set_nonblock(int fd)
+{
+       if (fcntl(fd, F_SETFL, fcntl(fd, F_GETFL)|O_NONBLOCK) != 0)
+               err(1, "Setting pipe nonblocking");
+}
+
+static bool handle_backoff(struct op *op[], int fd)
+{
+       struct op_desc desc;
+       bool handled = false;
+
+       /* Sloppy coding: we assume PIPEBUF never fills. */
+       while (read(fd, &desc, sizeof(desc)) != -1) {
+               unsigned int i;
+               handled = true;
+               for (i = desc.op_num; i > 0; i--) {
+                       if (op[desc.file][i].type == OP_TDB_TRAVERSE) {
+                               /* We insert a fake end here. */
+                               op[desc.file][i].type
+                                       = OP_TDB_TRAVERSE_END_EARLY;
+                               break;
+                       } else if (starts_traverse(&op[desc.file][i])) {
+                               unsigned int start = i;
+                               struct op tmp = op[desc.file][i];
+                               /* Move the ops outside traverse. */
+                               memmove(&op[desc.file][i],
+                                       &op[desc.file][i+1],
+                                       (desc.op_num-i-1) * sizeof(op[0][0]));
+                               op[desc.file][desc.op_num] = tmp;
+                               while (op[desc.file][i].group_start == start) {
+                                       op[desc.file][i++].group_start
+                                               = desc.op_num;
+                               }
+                               break;
+                       }
+               }
+       }
+       return handled;
+}
+
+#else /* !TRAVERSALS_TAKE_TRANSACTION_LOCK */
+static bool handle_backoff(struct op *op[], int fd)
+{
+       return false;
+}
+#endif
+
+static void derive_dependencies(struct tdb_context *tdb,
+                               char *filename[],
+                               struct op *op[], unsigned int num_ops[],
+                               unsigned int num)
+{
+       struct keyinfo *hash;
+       unsigned int h, i;
+
+       /* Create hash table for faster key lookup. */
+       hash = hash_ops(op, num_ops, num);
+
+       /* Sort them by sequence number. */
+       sort_ops(tdb, hash, filename, op, num);
+
+       /* Create dependencies back to the last change, rather than
+        * creating false dependencies by naively making each one
+        * depend on the previous.  This has two purposes: it makes
+        * later optimization simpler, and it also avoids deadlock with
+        * same sequence number ops inside traversals (if one
+        * traversal doesn't write anything, two ops can have the same
+        * sequence number yet we can create a traversal dependency
+        * the other way). */
+       for (h = 0; h < total_keys * 2; h++) {
+               int prev = -1;
+
+               if (hash[h].num_users < 2)
+                       continue;
+
+               for (i = 0; i < hash[h].num_users; i++) {
+                       if (changes_db(&hash[h].key, &op[hash[h].user[i].file]
+                                      [hash[h].user[i].op_num])) {
+                               depend_on_previous(op, filename, num,
+                                                  hash[h].user, i, prev);
+                               prev = i;
+                       } else if (prev >= 0)
+                               add_dependency(hash, op, filename,
+                                              &hash[h].user[i],
+                                              &hash[h].user[prev]);
+               }
+       }
+
+#if TRAVERSALS_TAKE_TRANSACTION_LOCK
+       make_traverse_depends(filename, op, num_ops, num);
+#endif
+
+       optimize_dependencies(op, num_ops, num);
+}
+
+static struct timeval run_test(char *argv[],
+                              unsigned int num_ops[],
+                              unsigned int hashsize[],
+                              unsigned int tdb_flags[],
+                              unsigned int open_flags[],
+                              struct op *op[],
+                              int fds[2])
+{
+       unsigned int i;
+       struct timeval start, end, diff;
+       bool ok = true;
+
+       for (i = 0; argv[i+2]; i++) {
                struct tdb_context *tdb;
+               char c;
 
                switch (fork()) {
                case -1:
                        err(1, "fork failed");
                case 0:
                        close(fds[1]);
-                       tdb = tdb_open_ex(argv[1], hashsize[i], tdb_flags[i],
-                                         open_flags[i], 0600,
-                                         NULL, hash_key);
+                       tdb = tdb_open(argv[1], hashsize[i],
+                                      tdb_flags[i], open_flags[i], 0600);
                        if (!tdb)
                                err(1, "Opening tdb %s", argv[1]);
 
                        /* This catches parent exiting. */
                        if (read(fds[0], &c, 1) != 1)
                                exit(1);
-                       run_ops(tdb, pipes[i].fd[0], argv[2+i],
-                               op[i], 1, num_ops[i]);
+                       run_ops(tdb, pipes[i].fd[0], argv+2, op, i, 1,
+                               num_ops[i], false);
+                       check_deps(argv[2+i], op[i], num_ops[i]);
                        exit(0);
                default:
                        break;
@@ -930,24 +1790,166 @@ int main(int argc, char *argv[])
        /* Let everything settle. */
        sleep(1);
 
+       if (!quiet)
+               printf("Starting run...");
+       fflush(stdout);
        gettimeofday(&start, NULL);
        /* Tell them all to go!  Any write of sufficient length will do. */
-       if (write(fds[1], hashsize, i) != 1)
+       if (write(fds[1], hashsize, i) != i)
                err(1, "Writing to wakeup pipe");
 
-       for (i = 0; i < argc - 2; i++) {
+       for (i = 0; argv[i + 2]; i++) {
                int status;
                wait(&status);
-               if (!WIFEXITED(status))
-                       errx(1, "Child died with signal");
-               if (WEXITSTATUS(status) != 0)
-                       errx(1, "Child died with error code");
+               if (!WIFEXITED(status)) {
+                       warnx("Child died with signal %i", WTERMSIG(status));
+                       ok = false;
+               } else if (WEXITSTATUS(status) != 0)
+                       /* Assume child spat out error. */
+                       ok = false;
        }
+       if (!ok)
+               exit(1);
+
        gettimeofday(&end, NULL);
+       if (!quiet)
+               printf("done\n");
+
+       if (end.tv_usec < start.tv_usec) {
+               end.tv_usec += 1000000;
+               end.tv_sec--;
+       }
+       diff.tv_sec = end.tv_sec - start.tv_sec;
+       diff.tv_usec = end.tv_usec - start.tv_usec;
+       return diff;
+}
+
+static void init_tdb(struct tdb_context *master_tdb,
+                    const char *name, unsigned int hashsize)
+{
+       TDB_DATA key, data;
+       struct tdb_context *tdb;
+
+       tdb = tdb_open(name, hashsize, TDB_CLEAR_IF_FIRST|TDB_NOSYNC,
+                      O_CREAT|O_TRUNC|O_RDWR, 0600);
+       if (!tdb)
+               errx(1, "opening tdb %s", name);
+
+       for (key = tdb_firstkey(master_tdb);
+            key.dptr;
+            key = tdb_nextkey(master_tdb, key)) {
+               data = tdb_fetch(master_tdb, key);
+               if (tdb_store(tdb, key, data, TDB_INSERT) != 0)
+                       errx(1, "Failed to store initial key");
+       }
+       tdb_close(tdb);
+}
+
+int main(int argc, char *argv[])
+{
+       struct timeval diff;
+       unsigned int i, num_ops[argc], hashsize[argc], tdb_flags[argc], open_flags[argc];
+       struct op *op[argc];
+       int fds[2];
+       struct tdb_context *master;
+       unsigned int runs = 1;
+
+       if (argc < 3)
+               errx(1, "Usage: %s [--quiet] [-n <number>] <tdbfile> <tracefile>...", argv[0]);
+
+       if (streq(argv[1], "--quiet")) {
+               quiet = true;
+               argv++;
+               argc--;
+       }
+       if (streq(argv[1], "-n")) {
+               runs = atoi(argv[2]);
+               argv += 2;
+               argc -= 2;
+       }
+
+       pipes = talloc_array(NULL, struct pipe, argc - 1);
+       for (i = 0; i < argc - 2; i++) {
+               if (!quiet)
+                       printf("Loading tracefile %s...", argv[2+i]);
+               fflush(stdout);
+               op[i] = load_tracefile(argv+2, i, &num_ops[i], &hashsize[i],
+                                      &tdb_flags[i], &open_flags[i]);
+               if (pipe(pipes[i].fd) != 0)
+                       err(1, "creating pipe");
+               /* Don't truncate, or clear if first: we do that. */
+               open_flags[i] &= ~(O_TRUNC);
+               tdb_flags[i] &= ~(TDB_CLEAR_IF_FIRST);
+               /* Open NOSYNC, to save time. */
+               tdb_flags[i] |= TDB_NOSYNC;
+               if (!quiet)
+                       printf("done\n");
+       }
+
+       /* Dependency may figure we need to create seed records. */
+       master = tdb_open(NULL, 0, TDB_INTERNAL, O_RDWR, 0);
+       if (!quiet) {
+               printf("Calculating inter-dependencies...");
+               fflush(stdout);
+       }
+       derive_dependencies(master, argv+2, op, num_ops, i);
+       if (!quiet)
+               printf("done\n");
+
+       for (i = 0; i < runs; i++) {
+               init_tdb(master, argv[1], hashsize[0]);
+
+               /* Don't fork for single arg case: simple debugging. */
+               if (argc == 3) {
+                       struct timeval start, end;
+                       struct tdb_context *tdb;
+
+                       tdb = tdb_open(argv[1], hashsize[0], tdb_flags[0],
+                                      open_flags[0], 0600);
+                       if (!quiet) {
+                               printf("Single threaded run...");
+                               fflush(stdout);
+                       }
+                       gettimeofday(&start, NULL);
+
+                       run_ops(tdb, pipes[0].fd[0], argv+2, op, 0, 1,
+                               num_ops[0], false);
+                       gettimeofday(&end, NULL);
+                       if (!quiet)
+                               printf("done\n");
+                       tdb_close(tdb);
+
+                       check_deps(argv[2], op[0], num_ops[0]);
+                       if (end.tv_usec < start.tv_usec) {
+                               end.tv_usec += 1000000;
+                               end.tv_sec--;
+                       }
+                       diff.tv_sec = end.tv_sec - start.tv_sec;
+                       diff.tv_usec = end.tv_usec - start.tv_usec;
+                       goto print_time;
+               }
+
+               if (pipe(fds) != 0)
+                       err(1, "creating pipe");
+
+#if TRAVERSALS_TAKE_TRANSACTION_LOCK
+               if (pipe(pipes[argc-2].fd) != 0)
+                       err(1, "creating pipe");
+               backoff_fd = pipes[argc-2].fd[1];
+               set_nonblock(pipes[argc-2].fd[1]);
+               set_nonblock(pipes[argc-2].fd[0]);
+#endif
+
+               do {
+                       diff = run_test(argv, num_ops, hashsize, tdb_flags,
+                                       open_flags, op, fds);
+               } while (handle_backoff(op, pipes[argc-2].fd[0]));
+
+       print_time:
+               if (!quiet)
+                       printf("Time replaying: ");
+               printf("%lu usec\n", diff.tv_sec * 1000000UL + diff.tv_usec);
+       }
 
-       end.tv_sec -= start.tv_sec;
-       printf("Time replaying: %lu usec\n",
-              end.tv_sec * 1000000UL + (end.tv_usec - start.tv_usec));
-       
        exit(0);
 }