/* Avoid mod by zero */
static unsigned int total_keys = 1;
-#define DEBUG_DEPS 1
+/* #define DEBUG_DEPS 1 */
/* Traversals block transactions in the current implementation. */
#define TRAVERSALS_TAKE_TRANSACTION_LOCK 1
}
/* 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;
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) {
+ warnx("%s:%u:avoiding deadlock",
+ filename[file], i+1);
+ return false;
+ }
dump_pre(filename, op, file, i);
exit(1);
} else
/* This could be any op, not just this one. */
talloc_free(dep);
}
+ return true;
}
static void do_post(char *filename[], struct op *op[],
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;
{
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. */
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. */
+ if (tinfo->op[tinfo->file][tinfo->i].op != OP_TDB_TRAVERSE)
return 1;
return 0;
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;
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;
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) {
case OP_TDB_LOCKALL:
}
+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 struct op *op, const TDB_DATA *pre)
+static const TDB_DATA *gives(const TDB_DATA *key, const TDB_DATA *pre,
+ const struct op *op)
{
+ if (is_transaction(op)) {
+ unsigned int i;
+
+ /* Cancelled transactions don't change anything. */
+ if (op[op->group_len].op == OP_TDB_TRANSACTION_CANCEL)
+ return pre;
+ assert(op[op->group_len].op == OP_TDB_TRANSACTION_COMMIT);
+
+ 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))
+ pre = gives(key, pre, &op[i]);
+ }
+ return pre;
+ }
+
/* Failed ops don't change state of db. */
if (op->ret < 0)
return pre;
return pre;
}
+static bool in_transaction(const struct op op[], unsigned int i)
+{
+ return op[i].group_start && is_transaction(&op[op[i].group_start]);
+}
+
+static bool in_traverse(const struct op op[], unsigned int i)
+{
+ return op[i].group_start && !is_transaction(&op[op[i].group_start]);
+}
+
static struct keyinfo *hash_ops(struct op *op[], unsigned int num_ops[],
unsigned int num)
{
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;
+
+ /* 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++;
}
return hash;
}
-static bool satisfies(const TDB_DATA *data, const TDB_DATA *need)
+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);
+
/* Don't need anything? Cool. */
if (!need)
return true;
assert(data != &must_not_exist);
assert(data != ¬_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 == ¬_exists_or_empty)
return key_eq(*data, *need);
}
-static void move_to_front(struct key_user res[], unsigned int elem)
+static void move_to_front(struct key_user res[], unsigned off, unsigned elem)
{
- if (elem != 0) {
+ if (elem != off) {
struct key_user tmp = res[elem];
- memmove(res + 1, res, elem*sizeof(res[0]));
- res[0] = tmp;
+ memmove(res + off + 1, res + off, (elem - off)*sizeof(res[0]));
+ res[off] = tmp;
}
}
-static void restore_to_pos(struct key_user res[], unsigned int elem)
+static void restore_to_pos(struct key_user res[], unsigned off, unsigned elem)
{
- if (elem != 0) {
- struct key_user tmp = res[0];
- memmove(res, res + 1, elem*sizeof(res[0]));
+ if (elem != off) {
+ struct key_user 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[], unsigned num,
- const TDB_DATA *data, unsigned num_files)
+ struct key_user 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];
- /* Nothing left? We're sorted. */
- if (num == 0)
+ /* Does this make serial numbers 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;
+
+ if (serial1 - serial2 > (int)fuzz) {
+#if DEBUG_DEPS
+ printf("Serial jump too far (%u -> %u)\n",
+ serial1, serial2);
+#endif
+ return false;
+ }
+ }
+
+ /* One or none left? We're sorted. */
+ if (off + 1 >= num)
return true;
memset(done, 0, sizeof(done));
* 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. */
- for (files_done = 0, i = 0; i < num && files_done < num_files; i++) {
+ 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(data, needs(this_op))) {
- move_to_front(res, i);
- if (sort_deps(filename, op, res+1, num-1,
- gives(this_op, data), num_files))
+ 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, i);
+ restore_to_pos(res, off, i);
}
done[res[i].file] = true;
files_done++;
* 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 num_users,
- unsigned num_files)
+ const TDB_DATA *key, struct key_user user[],
+ unsigned num_users, unsigned num_files)
{
/* We assume database starts empty. */
const struct TDB_DATA *data = &tdb_null;
+ unsigned int fuzz;
- if (!sort_deps(filename, op, user, num_users, data, num_files))
+ /* We prefer to keep strict serial 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)
fail(filename[user[0].file], user[0].op_num+1,
"Could not resolve inter-dependencies");
struct key_user *user = hash[h].user;
qsort(user, hash[h].num_users, sizeof(user[0]), compare_serial);
- figure_deps(filename, op, user, hash[h].num_users, num);
+ figure_deps(filename, op, &hash[h].key, user, hash[h].num_users,
+ num);
}
}
unsigned int satisfies_opnum)
{
struct depend *dep;
- unsigned int needs_start, sat_start;
/* We don't depend on ourselves. */
if (needs_file == satisfies_file) {
filename[satisfies_file], satisfies_opnum+1);
#endif
- needs_start = op[needs_file][needs_opnum].group_start;
- sat_start = op[satisfies_file][satisfies_opnum].group_start;
+#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;
+
+ /* We are satisfied by end of group. */
+ sat = op[satisfies_file][satisfies_opnum].group_start;
+ satisfies_opnum = sat + op[satisfies_file][sat].group_len;
+ /* And we need that done by start of our group. */
+ needs_opnum = op[needs_file][needs_opnum].group_start;
+ }
- /* If needs is in a transaction, we need it before start. */
- if (needs_start) {
- switch (op[needs_file][needs_start].op) {
- case OP_TDB_TRANSACTION_START:
- needs_opnum = needs_start;
-#ifdef DEBUG_DEPS
- printf(" -> Back to %u\n", needs_start+1);
- fflush(stdout);
-#endif
- break;
- default:
- break;
+ /* 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_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;
}
}
+#endif
- /* If satisfies is in a transaction, we wait until after commit. */
- /* FIXME: If transaction is cancelled, don't need dependency. */
- if (sat_start) {
- if (op[satisfies_file][sat_start].op
- == OP_TDB_TRANSACTION_START) {
- satisfies_opnum = sat_start
- + op[satisfies_file][sat_start].group_len;
-#ifdef DEBUG_DEPS
- printf(" -> Depends on %u\n", satisfies_opnum+1);
- fflush(stdout);
+ /* 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 DEBUG_DEPS
+ printf("-> Actually end of transaction %s:%u\n",
+ filename[satisfies_file], satisfies_opnum+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
+ == OP_TDB_TRANSACTION_COMMIT
+ || op[satisfies_file][satisfies_opnum].op
+ == OP_TDB_TRANSACTION_CANCEL);
assert(op[needs_file][needs_opnum].op != OP_TDB_TRAVERSE);
assert(op[satisfies_file][satisfies_opnum].op != OP_TDB_TRAVERSE);
talloc_set_destructor(dep, destroy_depend);
}
-#if TRAVERSALS_TAKE_TRANSACTION_LOCK
-struct traverse_dep {
- unsigned int file;
- unsigned int op_num;
-};
-
-/* Traversals can deadlock against each other, and transactions. Force
- * order. */
-static void make_traverse_depends(char *filename[],
- struct op *op[], unsigned int num_ops[],
- unsigned int num)
+static bool changes_db(const TDB_DATA *key, const struct op *op)
{
- unsigned int i, j, num_traversals = 0;
- struct traverse_dep *dep;
-
- /* Sort by which one runs first. */
- int compare_traverse_dep(const void *_a, const void *_b)
- {
- const struct traverse_dep *ta = _a, *tb = _b;
- const struct op *a = &op[ta->file][ta->op_num],
- *b = &op[tb->file][tb->op_num];
-
- if (a->serial != b->serial)
- return a->serial - b->serial;
-
- /* If they have same serial, it means one didn't make any
- * changes. Thus sort by end in that case. */
- return a[a->group_len].serial - b[b->group_len].serial;
- }
-
- dep = talloc_array(NULL, struct traverse_dep, 1);
-
- /* Count them. */
- for (i = 0; i < num; i++) {
- for (j = 1; j < num_ops[i]; j++) {
- /* Transaction or traverse start. */
- if (op[i][j].group_start == j) {
- dep = talloc_realloc(NULL, dep,
- struct traverse_dep,
- num_traversals+1);
- dep[num_traversals].file = i;
- dep[num_traversals].op_num = j;
- num_traversals++;
- }
- }
- }
- qsort(dep, num_traversals, sizeof(dep[0]), compare_traverse_dep);
- for (i = 1; i < num_traversals; i++) {
- /* i depends on end of traverse i-1. */
- add_dependency(NULL, op, filename, dep[i].file, dep[i].op_num,
- dep[i-1].file, dep[i-1].op_num
- + op[dep[i-1].file][dep[i-1].op_num].group_len);
- }
- talloc_free(dep);
-}
-#endif /* TRAVERSALS_TAKE_TRANSACTION_LOCK */
-
-static bool changes_db(const struct op *op)
-{
- return gives(op, NULL) != NULL;
+ return gives(key, NULL, op) != NULL;
}
static void depend_on_previous(struct op *op[],
continue;
for (i = 0; i < hash[h].num_users; i++) {
- if (changes_db(&op[hash[h].user[i].file]
+ 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);
}
}
-#if TRAVERSALS_TAKE_TRANSACTION_LOCK
- make_traverse_depends(filename, op, num_ops, num);
-#endif
-
optimize_dependencies(op, num_ops, num);
}
/* 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);
+ tdb = tdb_open_ex(argv[1], hashsize[0], tdb_flags[0]|TDB_NOSYNC,
+ 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]);
+ run_ops(tdb, pipes[0].fd[0], argv+2, op, 0, 1, num_ops[0],
+ false);
check_deps(argv[2], op[0], num_ops[0]);
printf("done\n");
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_ex(argv[1], hashsize[i],
+ tdb_flags[i]|TDB_NOSYNC,
+ open_flags[i], 0600, NULL, hash_key);
if (!tdb)
err(1, "Opening tdb %s", argv[1]);
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:
projects / ccan / blobdiff