X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Ftdb%2Ftools%2Freplay_trace.c;h=0e799a686158fef4bc8c6a8229285d1387cec95a;hp=e639dcdc6ce656e132230c2057003431daa76623;hb=100444225380d3f5ca29424ea54703d308c7c651;hpb=f2050233ad3b995baf239715457b53d64ebbf106

diff --git a/ccan/tdb/tools/replay_trace.c b/ccan/tdb/tools/replay_trace.c
index e639dcdc..0e799a68 100644
--- a/ccan/tdb/tools/replay_trace.c
+++ b/ccan/tdb/tools/replay_trace.c
@@ -15,14 +15,21 @@
 #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;
 
-#define DEBUG_DEPS 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
@@ -31,6 +38,7 @@ 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,
@@ -114,20 +122,23 @@ 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;
@@ -147,10 +158,16 @@ struct op {
 			TDB_DATA pre;
 			TDB_DATA post;
 		} append;
-		unsigned int group_len; /* transaction/traverse start */
+		/* 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);
@@ -187,90 +204,111 @@ 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->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, 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]);
 
 	op[op_num].append.post
-		= make_tdb_data(op, filename, op_num+1, words[5]);
+		= make_tdb_data(op, filename[file], 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;
@@ -279,50 +317,89 @@ static void op_add_append(const char *filename,
 	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].group_len = 0;
 }
 
-static void op_add_transaction(const char *filename, struct op op[],
-			       unsigned int op_num, char *words[])
+static void op_add_transaction(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].group_len = 0;
+}
+
+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");
 
+	/* 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;
 }
 
-static int op_transaction_start(struct op op[], unsigned int op_num)
+static void op_add_chainlock_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[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++;
+}
+
+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++;
+}
+
+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].op == OP_TDB_TRANSACTION_START && !op[i].group_len)
+		if (op[i].type == type && !op[i].group_len)
 			return i;
 	}
 	return 0;
 }
 
-static void op_analyze_transaction(const char *filename,
-				   struct op op[], unsigned int op_num,
+static void op_analyze_transaction(char *filename[], struct op op[],
+				   unsigned file, unsigned op_num,
 				   char *words[])
 {
 	unsigned int start, i;
@@ -330,11 +407,11 @@ static void op_analyze_transaction(const char *filename,
 	op[op_num].key = tdb_null;
 
 	if (words[2])
-		fail(filename, op_num+1, "Expect no arguments");
+		fail(filename[file], op_num+1, "Expect no arguments");
 
-	start = op_transaction_start(op, op_num);
+	start = op_find_start(op, op_num, OP_TDB_TRANSACTION_START);
 	if (!start)
-		fail(filename, op_num+1, "no transaction start found");
+		fail(filename[file], op_num+1, "no transaction start found");
 
 	op[start].group_len = op_num - start;
 
@@ -343,14 +420,37 @@ static void op_analyze_transaction(const char *filename,
 		op[i].group_start = start;
 }
 
-struct traverse_hash {
-	TDB_DATA key;
-	unsigned int index;
-};
+/* 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");
 
-static void op_analyze_traverse(const char *filename,
-				struct op op[], unsigned int op_num,
-				char *words[])
+	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;
 
@@ -359,28 +459,23 @@ static void op_analyze_traverse(const char *filename,
 	/* = %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;
 
-	for (i = op_num-1; i >= 0; i--) {
-		if (op[i].op != OP_TDB_TRAVERSE_READ_START
-		    && op[i].op != OP_TDB_TRAVERSE_START)
-			continue;
-		if (op[i].group_len)
-			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");
 
-	start = i;
 	op[start].group_len = op_num - start;
 
+	/* Don't roll in nested traverse/chainlock */
 	for (i = start; i <= op_num; i++)
-		op[i].group_start = start;
+		if (!op[i].group_start)
+			op[i].group_start = start;
 }
 
 /* Keep -Wmissing-declarations happy: */
@@ -393,10 +488,8 @@ struct depend {
 	/* We can have more than one */
 	struct list_node pre_list;
 	struct list_node post_list;
-	unsigned int needs_file;
-	unsigned int needs_opnum;
-	unsigned int satisfies_file;
-	unsigned int satisfies_opnum;
+	struct op_desc needs;
+	struct op_desc prereq;
 };
 
 static void check_deps(const char *filename, struct op op[], unsigned int num)
@@ -415,19 +508,22 @@ static void dump_pre(char *filename[], struct op *op[],
 {
 	struct depend *dep;
 
-	printf("%s:%u (%u) still waiting for:\n", filename[file], i+1,
-		op[file][i].serial);
-	list_for_each(&op[file][i].pre, dep, pre_list)
-		printf("    %s:%u (%u)\n",
-		       filename[dep->satisfies_file], dep->satisfies_opnum+1,
-		       op[dep->satisfies_file][dep->satisfies_opnum].serial);
+	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 void do_pre(struct tdb_context *tdb,
+static bool do_pre(struct tdb_context *tdb,
 		   char *filename[], struct op *op[],
-		   unsigned int file, int pre_fd, unsigned int i)
+		   unsigned int file, int pre_fd, unsigned int i,
+		   bool backoff)
 {
 	while (!list_empty(&op[file][i].pre)) {
 		struct depend *dep;
@@ -436,9 +532,21 @@ static void do_pre(struct tdb_context *tdb,
 		printf("%s:%u:waiting for pre\n", filename[file], i+1);
 		fflush(stdout);
 #endif
-		alarm(10);
+		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
@@ -448,13 +556,14 @@ static void do_pre(struct tdb_context *tdb,
 
 #if DEBUG_DEPS
 		printf("%s:%u:got pre %u from %s:%u\n", filename[file], i+1,
-		       dep->needs_opnum+1, filename[dep->satisfies_file],
-		       dep->satisfies_opnum+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[],
@@ -465,12 +574,12 @@ static void do_post(char *filename[], struct op *op[],
 	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_opnum+1);
+		       filename[dep->needs.file], dep->needs.op_num+1);
 #endif
-		if (write(pipes[dep->needs_file].fd[1], &dep, sizeof(dep))
+		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]);
+			    filename[file], i+1, filename[dep->needs.file]);
 	}
 }
 
@@ -484,7 +593,8 @@ static unsigned run_ops(struct tdb_context *tdb,
 			char *filename[],
 			struct op *op[],
 			unsigned int file,
-			unsigned int start, unsigned int stop);
+			unsigned int start, unsigned int stop,
+			bool backoff);
 
 struct traverse_info {
 	struct op **op;
@@ -502,6 +612,7 @@ static int nontrivial_traverse(struct tdb_context *tdb,
 {
 	struct traverse_info *tinfo = _tinfo;
 	unsigned int trav_len = tinfo->op[tinfo->file][tinfo->start].group_len;
+	bool avoid_deadlock = false;
 
 	if (tinfo->i == tinfo->start + trav_len) {
 		/* This can happen if traverse expects to be empty. */
@@ -511,15 +622,21 @@ static int nontrivial_traverse(struct tdb_context *tdb,
 		     "traverse did not terminate");
 	}
 
-	if (tinfo->op[tinfo->file][tinfo->i].op != OP_TDB_TRAVERSE)
+	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->file, tinfo->i+1, tinfo->start + trav_len);
+			   tinfo->file, tinfo->i+1, tinfo->start + trav_len,
+			   avoid_deadlock);
 
-	if (tinfo->i == tinfo->start + trav_len)
+	/* 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;
@@ -543,12 +660,14 @@ static unsigned op_traverse(struct tdb_context *tdb,
 	 * 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 != start + op[file][start].group_len) {
-		if (op[file][tinfo.i].op == OP_TDB_TRAVERSE)
+		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, file,
 					  tinfo.i,
-					  start + op[file][start].group_len);
+					  start + op[file][start].group_len,
+					  false);
 	}
 
 	return tinfo.i;
@@ -564,7 +683,8 @@ unsigned run_ops(struct tdb_context *tdb,
 		 char *filename[],
 		 struct op *op[],
 		 unsigned int file,
-		 unsigned int start, unsigned int stop)
+		 unsigned int start, unsigned int stop,
+		 bool backoff)
 {
 	unsigned int i;
 	struct sigaction sa;
@@ -574,9 +694,10 @@ unsigned run_ops(struct tdb_context *tdb,
 
 	sigaction(SIGALRM, &sa, NULL);
 	for (i = start; i < stop; i++) {
-		do_pre(tdb, filename, op, file, pre_fd, i);
+		if (!do_pre(tdb, filename, op, file, pre_fd, i, backoff))
+			return i;
 
-		switch (op[file][i].op) {
+		switch (op[file][i].type) {
 		case OP_TDB_LOCKALL:
 			try(tdb_lockall(tdb), op[file][i].ret);
 			break;
@@ -664,6 +785,10 @@ unsigned run_ops(struct tdb_context *tdb,
 		case OP_TDB_TRANSACTION_CANCEL:
 			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[file][i].ret);
 			break;
@@ -676,6 +801,7 @@ unsigned run_ops(struct tdb_context *tdb,
 					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;
@@ -701,6 +827,11 @@ unsigned run_ops(struct tdb_context *tdb,
 		case OP_TDB_DELETE:
 			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, file, i);
 	}
@@ -709,22 +840,24 @@ unsigned run_ops(struct tdb_context *tdb,
 
 /* tdbtorture, in particular, can do a tdb_close with a transaction in
  * progress. */
-static struct op *maybe_cancel_transaction(const char *filename,
+static struct op *maybe_cancel_transaction(char *filename[], unsigned int file,
 					   struct op *op, unsigned int *num)
 {
-	unsigned int start = op_transaction_start(op, *num);
+	unsigned int start = op_find_start(op, *num, OP_TDB_TRANSACTION_START);
 
 	if (start) {
 		char *words[] = { "<unknown>", "tdb_close", NULL };
-		add_op(filename, &op, *num, op[start].serial,
+		add_op(filename[file], &op, *num, op[start].seqnum,
 		       OP_TDB_TRANSACTION_CANCEL);
-		op_analyze_transaction(filename, op, *num, words);
+		op_analyze_transaction(filename, op, file, *num, words);
 		(*num)++;
 	}
 	return op;
 }
 
-static struct op *load_tracefile(const char *filename, unsigned int *num,
+static struct op *load_tracefile(char *filename[],
+				 unsigned int file,
+				 unsigned int *num,
 				 unsigned int *hashsize,
 				 unsigned int *tdb_flags,
 				 unsigned int *open_flags)
@@ -733,19 +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");
 	if (!lines[0])
-		errx(1, "%s is empty", filename);
+		errx(1, "%s is empty", filename[file]);
 
-	words = strsplit(lines, lines[0], " ", NULL);
+	words = strsplit(lines, lines[0], " ");
 	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);
@@ -754,47 +887,85 @@ static struct op *load_tracefile(const char *filename, unsigned int *num,
 	for (i = 1; lines[i]; i++) {
 		const struct op_table *opt;
 
-		words = strsplit(lines, lines[i], " ", NULL);
+		words = strsplit(lines, lines[i], " ");
 		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 maybe_cancel_transaction(filename,
+				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 maybe_cancel_transaction(filename, op, num);
+	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 starts_transaction(const struct op *op)
+{
+	return op->type == OP_TDB_TRANSACTION_START;
+}
+
+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;
@@ -802,9 +973,32 @@ 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 struct op *op)
+static const TDB_DATA *needs(const TDB_DATA *key, const struct op *op)
 {
-	switch (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:
@@ -868,32 +1062,29 @@ static const TDB_DATA *needs(const struct op *op)
 		return &must_exist;
 
 	default:
-		errx(1, "Unexpected op %i", op->op);
+		errx(1, "Unexpected op type %i", op->type);
 	}
 	
 }
 
-static bool is_transaction(const struct op *op)
-{
-	return op->op == OP_TDB_TRANSACTION_START;
-}
-
 /* 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 (is_transaction(op)) {
+	if (starts_transaction(op) || starts_chainlock(op)) {
 		unsigned int i;
 
 		/* Cancelled transactions don't change anything. */
-		if (op[op->group_len].op == OP_TDB_TRANSACTION_CANCEL)
+		if (op[op->group_len].type == OP_TDB_TRANSACTION_CANCEL)
 			return pre;
-		assert(op[op->group_len].op == OP_TDB_TRANSACTION_COMMIT);
+		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 (op[i].op != OP_TDB_TRAVERSE
-			    && key_eq(op[i].key, *key))
+			if (key_eq(op[i].key, *key)
+			    || op[i].type == OP_TDB_WIPE_ALL)
 				pre = gives(key, pre, &op[i]);
 		}
 		return pre;
@@ -903,26 +1094,45 @@ static const TDB_DATA *gives(const TDB_DATA *key, const TDB_DATA *pre,
 	if (op->ret < 0)
 		return pre;
 
-	if (op->op == OP_TDB_DELETE || op->op == OP_TDB_WIPE_ALL)
+	if (op->type == OP_TDB_DELETE || op->type == OP_TDB_WIPE_ALL)
 		return &tdb_null;
 
-	if (op->op == OP_TDB_APPEND)
+	if (op->type == OP_TDB_APPEND)
 		return &op->append.post;
 
-	if (op->op == OP_TDB_STORE)
+	if (op->type == OP_TDB_STORE)
 		return &op->data;
 
 	return pre;
 }
 
-static bool in_transaction(const struct op op[], unsigned int i)
+static void add_hash_user(struct keyinfo *hash,
+			  unsigned int h,
+			  struct op *op[],
+			  unsigned int file,
+			  unsigned int op_num)
 {
-	return op[i].group_start && is_transaction(&op[op[i].group_start]);
-}
+	hash[h].user = talloc_realloc(hash, hash[h].user,
+				      struct op_desc, hash[h].num_users+1);
 
-static bool in_traverse(const struct op op[], unsigned int i)
-{
-	return op[i].group_start && !is_transaction(&op[op[i].group_start]);
+	/* 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[],
@@ -941,11 +1151,6 @@ static struct keyinfo *hash_ops(struct op *op[], unsigned int num_ops[],
 			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) {
@@ -959,60 +1164,28 @@ 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);
-
-			/* If it's in a transaction, it's the transaction which
-			 * matters from an analysis POV. */
-			if (in_transaction(op[i], j)) {
-				unsigned start = op[i][j].group_start;
-
-				/* Don't include twice. */
-				if (hash[h].num_users
-				    && hash[h].user[hash[h].num_users-1].file
-					== i
-				    && hash[h].user[hash[h].num_users-1].op_num
-					== start)
-					continue;
 
-				hash[h].user[hash[h].num_users].op_num = start;
-			} else
-				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);
 		}
 	}
 
+	/* 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 bool satisfies(const TDB_DATA *key, const TDB_DATA *data,
 		      const struct op *op)
 {
-	const TDB_DATA *need = NULL;
-
-	if (is_transaction(op)) {
-		unsigned int i;
-
-		/* Look through for an op in this transaction which
-		 * needs this key. */
-		for (i = 1; i < op->group_len; i++) {
-			if (op[i].op != OP_TDB_TRAVERSE
-			    && key_eq(op[i].key, *key)) {
-				need = needs(&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].op != OP_TDB_EXISTS)
-					break;
-			}
-		}
-	} else
-		need = needs(op);
+	const TDB_DATA *need = needs(key, op);
 
 	/* Don't need anything?  Cool. */
 	if (!need)
@@ -1023,18 +1196,13 @@ static bool satisfies(const TDB_DATA *key, const TDB_DATA *data,
 	assert(data != &must_not_exist);
 	assert(data != &not_exists_or_empty);
 
-	/* must_not_exist == must_not_exist, must_exist == must_exist, or
-	   not_exists_or_empty == not_exists_or_empty. */
-	if (data->dsize == need->dsize && data->dptr == need->dptr)
-		return true;
-
 	/* Must not exist?  data must not exist. */
 	if (need == &must_not_exist)
-		return data->dptr == NULL;
+		return data == &tdb_null;
 
 	/* Must exist? */
 	if (need == &must_exist)
-		return data->dptr != NULL;
+		return data != &tdb_null;
 
 	/* Either noexist or empty. */
 	if (need == &not_exists_or_empty)
@@ -1044,26 +1212,26 @@ static bool satisfies(const TDB_DATA *key, const TDB_DATA *data,
 	return key_eq(*data, *need);
 }
 
-static void move_to_front(struct key_user res[], unsigned off, unsigned elem)
+static void move_to_front(struct op_desc res[], unsigned off, unsigned elem)
 {
 	if (elem != off) {
-		struct key_user tmp = res[elem];
+		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 key_user res[], unsigned off, unsigned elem)
+static void restore_to_pos(struct op_desc res[], unsigned off, unsigned elem)
 {
 	if (elem != off) {
-		struct key_user tmp = res[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 key_user res[],
+		      struct op_desc res[],
 		      unsigned off, unsigned num,
 		      const TDB_DATA *key, const TDB_DATA *data,
 		      unsigned num_files, unsigned fuzz)
@@ -1072,30 +1240,30 @@ static bool sort_deps(char *filename[], struct op *op[],
 	struct op *this_op;
 	bool done[num_files];
 
-	/* Does this make serial numbers go backwards?  Allow a little fuzz. */
+	/* 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 serial1 = op[res[off-1].file][res[off-1].op_num].serial;
-		int serial2 = op[res[off].file][res[off].op_num].serial;
+		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 (serial1 - serial2 > (int)fuzz) {
+		if (seqnum1 - seqnum2 > (int)fuzz) {
 #if DEBUG_DEPS
-			printf("Serial jump too far (%u -> %u)\n",
-			       serial1, serial2);
+			printf("Seqnum jump too far (%u -> %u)\n",
+			       seqnum1, seqnum2);
 #endif
 			return false;
 		}
 	}
 
-	/* One or none left?  We're sorted. */
-	if (off + 1 >= num)
-		return true;
-
 	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 serial 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;
@@ -1119,7 +1287,7 @@ static bool sort_deps(char *filename[], struct op *op[],
 	return false;
 }
 
-static void check_dep_sorting(struct key_user user[], unsigned num_users,
+static void check_dep_sorting(struct op_desc user[], unsigned num_users,
 			      unsigned num_files)
 {
 #if DEBUG_DEPS
@@ -1137,19 +1305,18 @@ static void check_dep_sorting(struct key_user user[], unsigned num_users,
 /* 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 serial number, and also due to race since we access the
+ * 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 void figure_deps(char *filename[], struct op *op[],
-			const TDB_DATA *key, struct key_user user[],
+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)
 {
-	/* We assume database starts empty. */
-	const struct TDB_DATA *data = &tdb_null;
 	unsigned int fuzz;
 
-	/* We prefer to keep strict serial order if possible: it's the
+	/* 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,
@@ -1158,38 +1325,86 @@ static void figure_deps(char *filename[], struct op *op[],
 	}
 
 	if (fuzz >= 100)
-		fail(filename[user[0].file], user[0].op_num+1,
-		     "Could not resolve inter-dependencies");
+		return false;
 
 	check_dep_sorting(user, num_users, num_files);
+	return true;
 }
 
-static void sort_ops(struct keyinfo hash[], char *filename[], struct op *op[],
+/* 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_serial(const void *_a, const void *_b)
+	int compare_seqnum(const void *_a, const void *_b)
 	{
-		const struct key_user *a = _a, *b = _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 serial order. */
-		return op[a->file][a->op_num].serial
-			- op[b->file][b->op_num].serial;
+		/* 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 serial order. */
+	/* Now sort into seqnum order. */
 	for (h = 0; h < total_keys * 2; h++) {
-		struct key_user *user = hash[h].user;
-
-		qsort(user, hash[h].num_users, sizeof(user[0]), compare_serial);
-		figure_deps(filename, op, &hash[h].key, user, hash[h].num_users,
-			    num);
+		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");
+		}
 	}
 }
 
@@ -1203,40 +1418,44 @@ static int destroy_depend(struct depend *dep)
 static void add_dependency(void *ctx,
 			   struct op *op[],
 			   char *filename[],
-			   unsigned int needs_file,
-			   unsigned int needs_opnum,
-			   unsigned int satisfies_file,
-			   unsigned int satisfies_opnum)
+			   const struct op_desc *needs,
+			   const struct op_desc *prereq)
 {
 	struct depend *dep;
 
 	/* We don't depend on ourselves. */
-	if (needs_file == satisfies_file) {
-		assert(satisfies_opnum < needs_opnum);
+	if (needs->file == prereq->file) {
+		assert(prereq->op_num < needs->op_num);
 		return;
 	}
 
 #if DEBUG_DEPS
 	printf("%s:%u: depends on %s:%u\n",
-	       filename[needs_file], needs_opnum+1,
-	       filename[satisfies_file], satisfies_opnum+1);
+	       filename[needs->file], needs->op_num+1,
+	       filename[prereq->file], prereq->op_num+1);
 #endif
 
+	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[satisfies_file], satisfies_opnum)
-	     && op[needs_file][needs_opnum].group_start)
-	    || (in_traverse(op[needs_file], needs_opnum)
-		&& op[satisfies_file][satisfies_opnum].group_start)) {
-		unsigned int sat;
+	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. */
-		sat = op[satisfies_file][satisfies_opnum].group_start;
-		satisfies_opnum = sat + op[satisfies_file][sat].group_len;
+		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. */
-		needs_opnum = op[needs_file][needs_opnum].group_start;
+		dep->needs.op_num = op[needs->file][needs->op_num].group_start;
 	}
 
 	/* There is also this case:
@@ -1248,42 +1467,38 @@ static void add_dependency(void *ctx,
 	 * 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_opnum)) {
-		struct op *need = &op[needs_file][needs_opnum];
-		if (op[needs_file][need->group_start].serial <
-		    op[satisfies_file][satisfies_opnum].serial) {
-			needs_opnum = need->group_start;
+	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, you actually depend on it ending. */
- 	if (is_transaction(&op[satisfies_file][satisfies_opnum])) {
- 		satisfies_opnum
- 			+= op[satisfies_file][satisfies_opnum].group_len;
+ 	/* 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[satisfies_file], satisfies_opnum+1);
+		       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[satisfies_file], satisfies_opnum)
-		       || op[satisfies_file][satisfies_opnum].op
+ 		assert(!in_transaction(op[prereq->file], dep->prereq.op_num)
+		       || op[prereq->file][dep->prereq.op_num].type
  		       == OP_TDB_TRANSACTION_COMMIT
- 		       || op[satisfies_file][satisfies_opnum].op
+ 		       || op[prereq->file][dep->prereq.op_num].type
  		       == OP_TDB_TRANSACTION_CANCEL);
 
-	assert(op[needs_file][needs_opnum].op != OP_TDB_TRAVERSE);
-	assert(op[satisfies_file][satisfies_opnum].op != OP_TDB_TRAVERSE);
-
-	dep = talloc(ctx, struct depend);
-	dep->needs_file = needs_file;
-	dep->needs_opnum = needs_opnum;
-	dep->satisfies_file = satisfies_file;
-	dep->satisfies_opnum = satisfies_opnum;
-	list_add(&op[satisfies_file][satisfies_opnum].post, &dep->post_list);
-	list_add(&op[needs_file][needs_opnum].pre, &dep->pre_list);
+	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);
 }
 
@@ -1295,7 +1510,7 @@ static bool changes_db(const TDB_DATA *key, const struct op *op)
 static void depend_on_previous(struct op *op[],
 			       char *filename[],
 			       unsigned int num,
-			       struct key_user user[],
+			       struct op_desc user[],
 			       unsigned int i,
 			       int prev)
 {
@@ -1307,9 +1522,7 @@ static void depend_on_previous(struct op *op[],
 
 	if (prev == i - 1) {
 		/* Just depend on previous. */
-		add_dependency(NULL, op, filename,
-			       user[i].file, user[i].op_num,
-			       user[prev].file, user[prev].op_num);
+		add_dependency(NULL, op, filename, &user[i], &user[prev]);
 		return;
 	}
 
@@ -1318,9 +1531,7 @@ static void depend_on_previous(struct op *op[],
 	deps[user[i].file] = true;
 	for (j = i - 1; j > prev; j--) {
 		if (!deps[user[j].file]) {
-			add_dependency(NULL, op, filename,
-				       user[i].file, user[i].op_num,
-				       user[j].file, user[j].op_num);
+			add_dependency(NULL, op, filename, &user[i], &user[j]);
 			deps[user[j].file] = true;
 		}
 	}
@@ -1342,14 +1553,14 @@ static void optimize_dependencies(struct op *op[], unsigned int num_ops[],
 			memset(prev, 0, sizeof(prev));
 
 			list_for_each_safe(&op[i][j].pre, dep, next, pre_list) {
-				if (!prev[dep->satisfies_file]) {
-					prev[dep->satisfies_file] = dep;
+				if (!prev[dep->prereq.file]) {
+					prev[dep->prereq.file] = dep;
 					continue;
 				}
-				if (prev[dep->satisfies_file]->satisfies_opnum
-				    < dep->satisfies_opnum) {
-					talloc_free(prev[dep->satisfies_file]);
-					prev[dep->satisfies_file] = dep;
+				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);
 			}
@@ -1366,18 +1577,132 @@ static void optimize_dependencies(struct op *op[], unsigned int num_ops[],
 			struct depend *dep, *next;
 
 			list_for_each_safe(&op[i][j].pre, dep, next, pre_list) {
-				if (deps[dep->satisfies_file]
-				    >= (int)dep->satisfies_opnum)
+				if (deps[dep->prereq.file]
+				    >= (int)dep->prereq.op_num)
 					talloc_free(dep);
 				else
-					deps[dep->satisfies_file]
-						= dep->satisfies_opnum;
+					deps[dep->prereq.file]
+						= dep->prereq.op_num;
 			}
 		}
 	}
 }
 
-static void derive_dependencies(char *filename[],
+#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)
 {
@@ -1387,8 +1712,8 @@ static void derive_dependencies(char *filename[],
 	/* Create hash table for faster key lookup. */
 	hash = hash_ops(op, num_ops, num);
 
-	/* Sort them by serial number. */
-	sort_ops(hash, filename, op, 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
@@ -1412,74 +1737,41 @@ static void derive_dependencies(char *filename[],
 				prev = i;
 			} else if (prev >= 0)
 				add_dependency(hash, op, filename,
-					       hash[h].user[i].file,
-					       hash[h].user[i].op_num,
-					       hash[h].user[prev].file,
-					       hash[h].user[prev].op_num);
+					       &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);
 }
 
-int main(int argc, char *argv[])
+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])
 {
-	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;
+	unsigned int i;
+	struct timeval start, end, diff;
 	bool ok = true;
 
-	if (argc < 3)
-		errx(1, "Usage: %s <tdbfile> <tracefile>...", argv[0]);
-
-	pipes = talloc_array(NULL, struct pipe, argc - 2);
-	for (i = 0; i < argc - 2; i++) {
-		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");
-		printf("done\n");
-	}
-
-	printf("Calculating inter-dependencies...");
-	fflush(stdout);
-	derive_dependencies(argv+2, op, num_ops, i);
-	printf("done\n");
-
-	/* 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);
-		printf("Single threaded run...");
-		fflush(stdout);
-
-		run_ops(tdb, pipes[0].fd[0], argv+2, op, 0, 1, num_ops[0]);
-		check_deps(argv[2], op[0], num_ops[0]);
-
-		printf("done\n");
-		exit(0);
-	}
-
-	if (pipe(fds) != 0)
-		err(1, "creating pipe");
-
-	for (i = 0; i < argc - 2; i++) {
+	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]);
 
@@ -1487,7 +1779,7 @@ int main(int argc, char *argv[])
 			if (read(fds[0], &c, 1) != 1)
 				exit(1);
 			run_ops(tdb, pipes[i].fd[0], argv+2, op, i, 1,
-				num_ops[i]);
+				num_ops[i], false);
 			check_deps(argv[2+i], op[i], num_ops[i]);
 			exit(0);
 		default:
@@ -1498,14 +1790,15 @@ int main(int argc, char *argv[])
 	/* Let everything settle. */
 	sleep(1);
 
-	printf("Starting run...");
+	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) != 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)) {
@@ -1519,11 +1812,144 @@ int main(int argc, char *argv[])
 		exit(1);
 
 	gettimeofday(&end, NULL);
-	printf("done\n");
+	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);
 }