Get more sophisticated with resolving duplicate serial numbers.
authorRusty Russell <rusty@rustcorp.com.au>
Sun, 12 Jul 2009 12:48:09 +0000 (22:18 +0930)
committerRusty Russell <rusty@rustcorp.com.au>
Sun, 12 Jul 2009 12:48:09 +0000 (22:18 +0930)
Still deadlocks in one case, due to spurious dependencies inside traversals.  See next commit.

ccan/tdb/tools/replay_trace.c

index 0bfaf6c5946ee7c50ed07c8cc7397a17eed3d8bd..f48c7d1f3474e56f0723606ef3a161cec577f813 100644 (file)
@@ -14,6 +14,7 @@
 #include <sys/time.h>
 #include <errno.h>
 #include <signal.h>
+#include <assert.h>
 
 #define STRINGIFY2(x) #x
 #define STRINGIFY(x) STRINGIFY2(x)
@@ -143,7 +144,10 @@ struct op {
        union {
                int flag; /* open and store */
                struct traverse *trav; /* traverse start */
-               TDB_DATA pre_append; /* append */
+               struct {  /* append */
+                       TDB_DATA pre;
+                       TDB_DATA post;
+               } append;
                unsigned int transaction_end; /* transaction start */
        };
 };
@@ -259,8 +263,6 @@ static void op_add_store(const char *filename,
 static void op_add_append(const char *filename,
                          struct op op[], unsigned int op_num, char *words[])
 {
-       TDB_DATA post_append;
-
        if (!words[2] || !words[3] || !words[4] || !words[5] || words[6]
            || !streq(words[4], "="))
                fail(filename, op_num+1, "Expect <key> <data> = <rec>");
@@ -268,11 +270,13 @@ static void op_add_append(const char *filename,
        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]);
 
-       post_append = make_tdb_data(op, filename, op_num+1, words[5]);
+       op[op_num].append.post
+               = make_tdb_data(op, filename, op_num+1, words[5]);
 
        /* By subtraction, figure out what previous data was. */
-       op[op_num].pre_append.dptr = post_append.dptr;
-       op[op_num].pre_append.dsize = post_append.dsize - op[op_num].data.dsize;
+       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++;
 }
 
@@ -737,11 +741,10 @@ unsigned run_ops(struct tdb_context *tdb,
                        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);
+                           op[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[i].key, op[i].data), op[i].ret);
                        break;
                case OP_TDB_GET_SEQNUM:
                        try(tdb_get_seqnum(tdb), op[i].ret);
@@ -888,9 +891,9 @@ static const TDB_DATA *needs(const struct op *op)
                return NULL;
 
        case OP_TDB_APPEND:
-               if (op->pre_append.dsize == 0)
+               if (op->append.pre.dsize == 0)
                        return &not_exists_or_empty;
-               return &op->pre_append;
+               return &op->append.pre;
 
        case OP_TDB_STORE:
                if (op->flag == TDB_INSERT) {
@@ -945,74 +948,23 @@ static const TDB_DATA *needs(const struct op *op)
        
 }
 
-enum satisfaction {
-       /* This op makes the other one possible. */
-       SATISFIES,
-       /* This op makes the other one impossible. */
-       DISSATISFIES,
-       /* This op makes no difference. */
-       NO_CHANGE
-};
-
-static enum satisfaction satisfies(const struct op *op, const TDB_DATA *need)
+/* What's the data after this op?  pre if nothing changed. */
+static const TDB_DATA *gives(const struct op *op, const TDB_DATA *pre)
 {
-       bool deletes, creates;
-
        /* Failed ops don't change state of db. */
        if (op->ret < 0)
-               return NO_CHANGE;
-
-       deletes = (op->op == OP_TDB_DELETE || op->op == OP_TDB_WIPE_ALL);
-       /* Append/store is creating the record if ret == 0 (1 means replaced) */
-       if (op->op == OP_TDB_APPEND || op->op == OP_TDB_STORE)
-               creates = (op->ret == 0);
-       else
-               creates = false;
-
-       if (need == &must_not_exist) {
-               if (deletes)
-                       return SATISFIES;
-               if (creates)
-                       return DISSATISFIES;
-               return NO_CHANGE;
-       }
+               return pre;
 
-       if (need == &must_exist) {
-               if (deletes)
-                       return DISSATISFIES;
-               if (creates) 
-                       return SATISFIES;
-               return NO_CHANGE;
-       }
+       if (op->op == OP_TDB_DELETE || op->op == OP_TDB_WIPE_ALL)
+               return &tdb_null;
 
-       if (need == &not_exists_or_empty) {
-               if (deletes)
-                       return SATISFIES;
-               if (!creates)
-                       return NO_CHANGE;
-       }
+       if (op->op == OP_TDB_APPEND)
+               return &op->append.post;
 
-       /* OK, we need an exact match. */
-       if (deletes)
-               return DISSATISFIES;
-
-       /* An append which results in the wrong data dissatisfies. */
-       if (op->op == OP_TDB_APPEND) {
-               if (op->pre_append.dsize + op->data.dsize != need->dsize)
-                       return DISSATISFIES;
-               if (memcmp(op->pre_append.dptr, need->dptr,
-                          op->pre_append.dsize) != 0)
-                       return DISSATISFIES;
-               if (memcmp(op->data.dptr, need->dptr + op->pre_append.dsize,
-                          op->data.dsize) != 0)
-                       return DISSATISFIES;
-               return SATISFIES;
-       } else if (op->op == OP_TDB_STORE) {
-               if (key_eq(op->data, *need))
-                       return SATISFIES;
-               return DISSATISFIES;
-       }
-       return NO_CHANGE;
+       if (op->op == OP_TDB_STORE)
+               return &op->data;
+
+       return pre;
 }
 
 static struct keyinfo *hash_ops(struct op *op[], unsigned int num_ops[],
@@ -1021,46 +973,6 @@ 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;
-
-               /* Serial is not completely reliable.  First, fetches don't
-                * inc serial, second we don't lock to get seq number.
-                * This smooths things a little for simple cases. */
-               if (ret == 0) {
-                       const TDB_DATA *a_needs, *b_needs;
-
-                       b_needs = needs(&op[b->file][b->op_num]);
-                       switch (satisfies(&op[a->file][a->op_num], b_needs)) {
-                       case SATISFIES:
-                               /* A comes first: it satisfies B. */
-                               return -1;
-                       case DISSATISFIES:
-                               /* A doesn't come first: it messes up B. */
-                               return 1;
-                       default:
-                               break;
-                       }
-
-                       a_needs = needs(&op[a->file][a->op_num]);
-                       switch (satisfies(&op[b->file][b->op_num], a_needs)) {
-                       case SATISFIES:
-                               /* B comes first: it satisfies A. */
-                               return 1;
-                       case DISSATISFIES:
-                               /* B doesn't come first: it messes up A. */
-                               return -1;
-                       default:
-                               break;
-                       }
-               }
-               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++) {
@@ -1098,12 +1010,127 @@ static struct keyinfo *hash_ops(struct op *op[], unsigned int num_ops[],
                }
        }
 
+       return hash;
+}
+
+static bool satisfies(const TDB_DATA *data, const TDB_DATA *need)
+{
+       /* 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 == 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;
+
+       /* Must exist? */
+       if (need == &must_exist)
+               return data->dptr != NULL;
+
+       /* Either noexist or empty. */
+       if (need == &not_exists_or_empty)
+               return data->dsize == 0;
+
+       /* Needs something specific. */
+       return key_eq(*data, *need);
+}
+
+static bool sort_deps(char *filename[], struct op *op[],
+                     struct key_user res[], unsigned num,
+                     const TDB_DATA *data)
+{
+       unsigned int i;
+
+       /* Nothing left?  We're sorted. */
+       if (num == 0)
+               return true;
+
+       for (i = 0; i < num; i++) {
+               struct op *this_op = &op[res[i].file][res[i].op_num];
+
+               /* Is what we have good enough for this op? */
+               if (satisfies(data, needs(this_op))) {
+                       /* Try this one next. */
+                       struct key_user tmp = res[0];
+                       res[0] = res[i];
+                       res[i] = tmp;
+                       if (sort_deps(filename, op, res+1, num-1,
+                                     gives(this_op, data)))
+                               return true;
+               }
+       }
+       /* No combination worked. */
+       return false;
+}
+
+/* All these ops have the same serial number.  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
+ * 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[],
+                       struct key_user user[], unsigned start, unsigned end)
+{
+       unsigned int i;
+       /* We assume database starts empty. */
+       const struct TDB_DATA *data = &tdb_null;
+
+       /* What do we have to start with? */
+       for (i = 0; i < start; i++)
+               data = gives(&op[user[i].file][user[i].op_num], data);
+
+       if (!sort_deps(filename, op, user + start, end - start, data))
+               fail(filename[user[start].file], user[start].op_num+1,
+                    "Could not resolve inter-dependencies");
+}
+
+static void sort_ops(struct keyinfo hash[], char *filename[], struct op *op[])
+{
+       unsigned int h;
+
+       /* Gcc nexted function extension.  How cool is this? */
+       int compare_serial(const void *_a, const void *_b)
+       {
+               const struct key_user *a = _a, *b = _b;
+               return op[a->file][a->op_num].serial
+                       - op[b->file][b->op_num].serial;
+       }
+
        /* 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);
+       for (h = 0; h < total_keys * 2; h++) {
+               unsigned int i, same;
+               struct key_user *user = hash[h].user;
 
-       return hash;
+               qsort(user, hash[h].num_users, sizeof(user[0]), compare_serial);
+
+               /* Try to deal with same serial numbers. */
+               for (i = 1, same = 0; i < hash[h].num_users; i++) {
+                       if (op[user[i].file][user[i].op_num].serial
+                           == op[user[i-1].file][user[i-1].op_num].serial) {
+                               same++;
+                               continue;
+                       }
+
+                       if (same) {
+                               figure_deps(filename, op, user, i-same-1, i);
+                               same = 0;
+                       }
+               }
+               if (same)
+                       figure_deps(filename, op, user, i-same-1, i);
+       }
 }
 
 static void add_dependency(void *ctx,