#include "btree_locking.h"
#include "btree_types.h"
-struct lock_class_key bch2_btree_node_lock_key;
+static struct lock_class_key bch2_btree_node_lock_key;
+
+void bch2_btree_lock_init(struct btree_bkey_cached_common *b)
+{
+ __six_lock_init(&b->lock, "b->c.lock", &bch2_btree_node_lock_key);
+}
+
+#ifdef CONFIG_LOCKDEP
+void bch2_assert_btree_nodes_not_locked(void)
+{
+ BUG_ON(lock_class_is_held(&bch2_btree_node_lock_key));
+}
+#endif
/* Btree node locking: */
unsigned nr;
};
-static void lock_graph_pop(struct lock_graph *g)
-{
- closure_put(&g->g[--g->nr].trans->ref);
-}
-
static noinline void print_cycle(struct printbuf *out, struct lock_graph *g)
{
struct trans_waiting_for_lock *i;
bch2_btree_trans_to_text(out, i->trans);
}
-static int abort_lock(struct lock_graph *g, struct trans_waiting_for_lock *i)
+static noinline void print_chain(struct printbuf *out, struct lock_graph *g)
{
- int ret;
+ struct trans_waiting_for_lock *i;
+
+ for (i = g->g; i != g->g + g->nr; i++) {
+ if (i != g->g)
+ prt_str(out, "<- ");
+ prt_printf(out, "%u ", i->trans->locking_wait.task->pid);
+ }
+ prt_newline(out);
+}
+
+static void lock_graph_up(struct lock_graph *g)
+{
+ closure_put(&g->g[--g->nr].trans->ref);
+}
+
+static noinline void lock_graph_pop_all(struct lock_graph *g)
+{
+ while (g->nr)
+ lock_graph_up(g);
+}
+
+static void lock_graph_down(struct lock_graph *g, struct btree_trans *trans)
+{
+ closure_get(&trans->ref);
+
+ g->g[g->nr++] = (struct trans_waiting_for_lock) {
+ .trans = trans,
+ .node_want = trans->locking,
+ .lock_want = trans->locking_wait.lock_want,
+ };
+}
+
+static bool lock_graph_remove_non_waiters(struct lock_graph *g)
+{
+ struct trans_waiting_for_lock *i;
+
+ for (i = g->g + 1; i < g->g + g->nr; i++)
+ if (i->trans->locking != i->node_want ||
+ i->trans->locking_wait.start_time != i[-1].lock_start_time) {
+ while (g->g + g->nr > i)
+ lock_graph_up(g);
+ return true;
+ }
+
+ return false;
+}
+static int abort_lock(struct lock_graph *g, struct trans_waiting_for_lock *i)
+{
if (i == g->g) {
trace_and_count(i->trans->c, trans_restart_would_deadlock, i->trans, _RET_IP_);
- ret = btree_trans_restart(i->trans, BCH_ERR_transaction_restart_would_deadlock);
+ return btree_trans_restart(i->trans, BCH_ERR_transaction_restart_would_deadlock);
} else {
i->trans->lock_must_abort = true;
- ret = 0;
+ wake_up_process(i->trans->locking_wait.task);
+ return 0;
}
+}
- for (i = g->g + 1; i < g->g + g->nr; i++)
- wake_up_process(i->trans->locking_wait.task);
- return ret;
+static int btree_trans_abort_preference(struct btree_trans *trans)
+{
+ if (trans->lock_may_not_fail)
+ return 0;
+ if (trans->locking_wait.lock_want == SIX_LOCK_write)
+ return 1;
+ if (!trans->in_traverse_all)
+ return 2;
+ return 3;
}
-static noinline int break_cycle(struct lock_graph *g)
+static noinline int break_cycle(struct lock_graph *g, struct printbuf *cycle)
{
- struct trans_waiting_for_lock *i;
+ struct trans_waiting_for_lock *i, *abort = NULL;
+ unsigned best = 0, pref;
+ int ret;
- for (i = g->g; i < g->g + g->nr; i++) {
- if (i->trans->lock_may_not_fail ||
- i->trans->locking_wait.lock_want == SIX_LOCK_write)
- continue;
+ if (lock_graph_remove_non_waiters(g))
+ return 0;
- return abort_lock(g, i);
+ /* Only checking, for debugfs: */
+ if (cycle) {
+ print_cycle(cycle, g);
+ ret = -1;
+ goto out;
}
for (i = g->g; i < g->g + g->nr; i++) {
- if (i->trans->lock_may_not_fail ||
- !i->trans->in_traverse_all)
- continue;
-
- return abort_lock(g, i);
+ pref = btree_trans_abort_preference(i->trans);
+ if (pref > best) {
+ abort = i;
+ best = pref;
+ }
}
- for (i = g->g; i < g->g + g->nr; i++) {
- if (i->trans->lock_may_not_fail)
- continue;
+ if (unlikely(!best)) {
+ struct printbuf buf = PRINTBUF;
+
+ prt_printf(&buf, bch2_fmt(g->g->trans->c, "cycle of nofail locks"));
+
+ for (i = g->g; i < g->g + g->nr; i++) {
+ struct btree_trans *trans = i->trans;
+
+ bch2_btree_trans_to_text(&buf, trans);
- return abort_lock(g, i);
+ prt_printf(&buf, "backtrace:");
+ prt_newline(&buf);
+ printbuf_indent_add(&buf, 2);
+ bch2_prt_task_backtrace(&buf, trans->locking_wait.task);
+ printbuf_indent_sub(&buf, 2);
+ prt_newline(&buf);
+ }
+
+ bch2_print_string_as_lines(KERN_ERR, buf.buf);
+ printbuf_exit(&buf);
+ BUG();
}
- BUG();
+ ret = abort_lock(g, abort);
+out:
+ if (ret)
+ while (g->nr)
+ lock_graph_up(g);
+ return ret;
}
static int lock_graph_descend(struct lock_graph *g, struct btree_trans *trans,
{
struct btree_trans *orig_trans = g->g->trans;
struct trans_waiting_for_lock *i;
- int ret = 0;
-
- for (i = g->g; i < g->g + g->nr; i++) {
- if (i->trans->locking != i->node_want)
- while (g->g + g->nr >= i) {
- lock_graph_pop(g);
- return 0;
- }
-
- if (i->trans == trans) {
- if (cycle) {
- /* Only checking: */
- print_cycle(cycle, g);
- ret = -1;
- } else {
- ret = break_cycle(g);
- }
- if (ret)
- goto deadlock;
- /*
- * If we didn't abort (instead telling another
- * transaction to abort), keep checking:
- */
- }
- }
+ for (i = g->g; i < g->g + g->nr; i++)
+ if (i->trans == trans)
+ return break_cycle(g, cycle);
if (g->nr == ARRAY_SIZE(g->g)) {
if (orig_trans->lock_may_not_fail)
return 0;
- trace_and_count(trans->c, trans_restart_would_deadlock_recursion_limit, trans, _RET_IP_);
- ret = btree_trans_restart(orig_trans, BCH_ERR_transaction_restart_deadlock_recursion_limit);
- goto deadlock;
- }
+ while (g->nr)
+ lock_graph_up(g);
- closure_get(&trans->ref);
+ if (cycle)
+ return 0;
- g->g[g->nr++] = (struct trans_waiting_for_lock) {
- .trans = trans,
- .node_want = trans->locking,
- .lock_want = trans->locking_wait.lock_want,
- };
+ trace_and_count(trans->c, trans_restart_would_deadlock_recursion_limit, trans, _RET_IP_);
+ return btree_trans_restart(orig_trans, BCH_ERR_transaction_restart_deadlock_recursion_limit);
+ }
+ lock_graph_down(g, trans);
return 0;
-deadlock:
- while (g->nr)
- lock_graph_pop(g);
- return ret;
-}
-
-static noinline void lock_graph_remove_non_waiters(struct lock_graph *g)
-{
- struct trans_waiting_for_lock *i;
-
- for (i = g->g + 1; i < g->g + g->nr; i++)
- if (i->trans->locking != i->node_want ||
- i->trans->locking_wait.start_time != i[-1].lock_start_time) {
- while (g->g + g->nr >= i)
- lock_graph_pop(g);
- return;
- }
- BUG();
}
static bool lock_type_conflicts(enum six_lock_type t1, enum six_lock_type t2)
int ret;
if (trans->lock_must_abort) {
+ if (cycle)
+ return -1;
+
trace_and_count(trans->c, trans_restart_would_deadlock, trans, _RET_IP_);
return btree_trans_restart(trans, BCH_ERR_transaction_restart_would_deadlock);
}
g.nr = 0;
- ret = lock_graph_descend(&g, trans, cycle);
- BUG_ON(ret);
+ lock_graph_down(&g, trans);
next:
if (!g.nr)
return 0;
b = &READ_ONCE(path->l[top->level].b)->c;
- if (unlikely(IS_ERR_OR_NULL(b))) {
- lock_graph_remove_non_waiters(&g);
+ if (IS_ERR_OR_NULL(b)) {
+ /*
+ * If we get here, it means we raced with the
+ * other thread updating its btree_path
+ * structures - which means it can't be blocked
+ * waiting on a lock:
+ */
+ if (!lock_graph_remove_non_waiters(&g)) {
+ /*
+ * If lock_graph_remove_non_waiters()
+ * didn't do anything, it must be
+ * because we're being called by debugfs
+ * checking for lock cycles, which
+ * invokes us on btree_transactions that
+ * aren't actually waiting on anything.
+ * Just bail out:
+ */
+ lock_graph_pop_all(&g);
+ }
+
goto next;
}
raw_spin_unlock(&b->lock.wait_lock);
if (ret)
- return ret < 0 ? ret : 0;
+ return ret;
goto next;
}
}
}
- lock_graph_pop(&g);
+ if (g.nr > 1 && cycle)
+ print_chain(cycle, &g);
+ lock_graph_up(&g);
goto next;
}
* locked:
*/
six_lock_readers_add(&b->lock, -readers);
- ret = __btree_node_lock_nopath(trans, b, SIX_LOCK_write, lock_may_not_fail);
+ ret = __btree_node_lock_nopath(trans, b, SIX_LOCK_write,
+ lock_may_not_fail, _RET_IP_);
six_lock_readers_add(&b->lock, readers);
if (ret)
return ret;
}
+void bch2_btree_node_lock_write_nofail(struct btree_trans *trans,
+ struct btree_path *path,
+ struct btree_bkey_cached_common *b)
+{
+ struct btree_path *linked;
+ unsigned i;
+ int ret;
+
+ /*
+ * XXX BIG FAT NOTICE
+ *
+ * Drop all read locks before taking a write lock:
+ *
+ * This is a hack, because bch2_btree_node_lock_write_nofail() is a
+ * hack - but by dropping read locks first, this should never fail, and
+ * we only use this in code paths where whatever read locks we've
+ * already taken are no longer needed:
+ */
+
+ trans_for_each_path(trans, linked) {
+ if (!linked->nodes_locked)
+ continue;
+
+ for (i = 0; i < BTREE_MAX_DEPTH; i++)
+ if (btree_node_read_locked(linked, i)) {
+ btree_node_unlock(trans, linked, i);
+ btree_path_set_dirty(linked, BTREE_ITER_NEED_RELOCK);
+ }
+ }
+
+ ret = __btree_node_lock_write(trans, path, b, true);
+ BUG_ON(ret);
+}
+
/* relock */
static inline bool btree_path_get_locks(struct btree_trans *trans,
return true;
}
fail:
- if (trace)
+ if (trace && !trans->notrace_relock_fail)
trace_and_count(trans->c, btree_path_relock_fail, trans, _RET_IP_, path, level);
return false;
}
return btree_path_get_locks(trans, path, false);
}
+int __bch2_btree_path_relock(struct btree_trans *trans,
+ struct btree_path *path, unsigned long trace_ip)
+{
+ if (!bch2_btree_path_relock_norestart(trans, path, trace_ip)) {
+ trace_and_count(trans->c, trans_restart_relock_path, trans, trace_ip, path);
+ return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock_path);
+ }
+
+ return 0;
+}
+
__flatten
bool bch2_btree_path_upgrade_norestart(struct btree_trans *trans,
struct btree_path *path, unsigned long trace_ip)
struct btree_path *path;
if (unlikely(trans->restarted))
- return - ((int) trans->restarted);
+ return -((int) trans->restarted);
trans_for_each_path(trans, path)
if (path->should_be_locked &&
return 0;
}
+int bch2_trans_relock_notrace(struct btree_trans *trans)
+{
+ struct btree_path *path;
+
+ if (unlikely(trans->restarted))
+ return -((int) trans->restarted);
+
+ trans_for_each_path(trans, path)
+ if (path->should_be_locked &&
+ !bch2_btree_path_relock_norestart(trans, path, _RET_IP_)) {
+ return btree_trans_restart(trans, BCH_ERR_transaction_restart_relock);
+ }
+ return 0;
+}
+
void bch2_trans_unlock(struct btree_trans *trans)
{
struct btree_path *path;
* bch2_gc_btree_init_recurse() doesn't use btree iterators for walking
* btree nodes, it implements its own walking:
*/
- BUG_ON(!trans->is_initial_gc &&
- lock_class_is_held(&bch2_btree_node_lock_key));
+ if (!trans->is_initial_gc)
+ bch2_assert_btree_nodes_not_locked();
+}
+
+bool bch2_trans_locked(struct btree_trans *trans)
+{
+ struct btree_path *path;
+
+ trans_for_each_path(trans, path)
+ if (path->nodes_locked)
+ return true;
+ return false;
+}
+
+int __bch2_trans_mutex_lock(struct btree_trans *trans,
+ struct mutex *lock)
+{
+ int ret;
+
+ bch2_trans_unlock(trans);
+ mutex_lock(lock);
+ ret = bch2_trans_relock(trans);
+ if (ret)
+ mutex_unlock(lock);
+ return ret;
}
/* Debug */
projects / bcachefs-tools-debian / blobdiff