Get more sophisticated with resolving duplicate serial numbers.

Still deadlocks in one case, due to spurious dependencies inside traversals.  See next commit.

ccan/tdb/tools/replay_trace.c

@@ -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,