diff --git a/src/core/lib/iomgr/timer_generic.c b/src/core/lib/iomgr/timer_generic.c
index e9a7236c8c2..2472cf26be3 100644
--- a/src/core/lib/iomgr/timer_generic.c
+++ b/src/core/lib/iomgr/timer_generic.c
@@ -79,6 +79,125 @@ static timer_shard g_shards[NUM_SHARDS];
* Access to this is protected by g_shared_mutables.mu */
static timer_shard *g_shard_queue[NUM_SHARDS];
+#ifndef NDEBUG
+
+/* == Hash table for duplicate timer detection == */
+
+#define NUM_HASH_BUCKETS 1009 /* Prime number close to 1000 */
+
+static gpr_mu g_hash_mu[NUM_HASH_BUCKETS]; /* One mutex per bucket */
+static grpc_timer *g_timer_ht[NUM_HASH_BUCKETS] = {NULL};
+
+static void init_timer_ht() {
+ for (int i = 0; i < NUM_HASH_BUCKETS; i++) {
+ gpr_mu_init(&g_hash_mu[i]);
+ }
+}
+
+static bool is_in_ht(grpc_timer *t) {
+ size_t i = GPR_HASH_POINTER(t, NUM_HASH_BUCKETS);
+
+ gpr_mu_lock(&g_hash_mu[i]);
+ grpc_timer *p = g_timer_ht[i];
+ while (p != NULL && p != t) {
+ p = p->hash_table_next;
+ }
+ gpr_mu_unlock(&g_hash_mu[i]);
+
+ return (p == t);
+}
+
+static void add_to_ht(grpc_timer *t) {
+ GPR_ASSERT(!t->hash_table_next);
+ size_t i = GPR_HASH_POINTER(t, NUM_HASH_BUCKETS);
+
+ gpr_mu_lock(&g_hash_mu[i]);
+ grpc_timer *p = g_timer_ht[i];
+ while (p != NULL && p != t) {
+ p = p->hash_table_next;
+ }
+
+ if (p == t) {
+ grpc_closure *c = t->closure;
+ gpr_log(GPR_ERROR,
+ "** Duplicate timer (%p) being added. Closure: (%p), created at: "
+ "(%s:%d), scheduled at: (%s:%d) **",
+ t, c, c->file_created, c->line_created, c->file_initiated,
+ c->line_initiated);
+ abort();
+ }
+
+ /* Timer not present in the bucket. Insert at head of the list */
+ t->hash_table_next = g_timer_ht[i];
+ g_timer_ht[i] = t;
+ gpr_mu_unlock(&g_hash_mu[i]);
+}
+
+static void remove_from_ht(grpc_timer *t) {
+ size_t i = GPR_HASH_POINTER(t, NUM_HASH_BUCKETS);
+ bool removed = false;
+
+ gpr_mu_lock(&g_hash_mu[i]);
+ if (g_timer_ht[i] == t) {
+ g_timer_ht[i] = g_timer_ht[i]->hash_table_next;
+ removed = true;
+ } else if (g_timer_ht[i] != NULL) {
+ grpc_timer *p = g_timer_ht[i];
+ while (p->hash_table_next != NULL && p->hash_table_next != t) {
+ p = p->hash_table_next;
+ }
+
+ if (p->hash_table_next == t) {
+ p->hash_table_next = t->hash_table_next;
+ removed = true;
+ }
+ }
+ gpr_mu_unlock(&g_hash_mu[i]);
+
+ if (!removed) {
+ grpc_closure *c = t->closure;
+ gpr_log(GPR_ERROR,
+ "** Removing timer (%p) that is not added to hash table. Closure "
+ "(%p), created at: (%s:%d), scheduled at: (%s:%d) **",
+ t, c, c->file_created, c->line_created, c->file_initiated,
+ c->line_initiated);
+ abort();
+ }
+
+ t->hash_table_next = NULL;
+}
+
+/* If a timer is added to a timer shard (either heap or a list), it cannot
+ * be pending. A timer is added to hash table only-if it is added to the
+ * timer shard.
+ * Therefore, if timer->pending is false, it cannot be in hash table */
+static void validate_non_pending_timer(grpc_timer *t) {
+ if (!t->pending && is_in_ht(t)) {
+ grpc_closure *c = t->closure;
+ gpr_log(GPR_ERROR,
+ "** gpr_timer_cancel() called on a non-pending timer (%p) which "
+ "is in the hash table. Closure: (%p), created at: (%s:%d), "
+ "scheduled at: (%s:%d) **",
+ t, c, c->file_created, c->line_created, c->file_initiated,
+ c->line_initiated);
+ abort();
+ }
+}
+
+#define INIT_TIMER_HASH_TABLE() init_timer_ht()
+#define ADD_TO_HASH_TABLE(t) add_to_ht((t))
+#define REMOVE_FROM_HASH_TABLE(t) remove_from_ht((t))
+#define VALIDATE_NON_PENDING_TIMER(t) validate_non_pending_timer((t))
+
+#else
+
+#define INIT_TIMER_HASH_TABLE()
+#define ADD_TO_HASH_TABLE(t)
+#define REMOVE_FROM_HASH_TABLE(t)
+#define VALIDATE_NON_PENDING_TIMER(t)
+
+#endif
+
/* Thread local variable that stores the deadline of the next timer the thread
* has last-seen. This is an optimization to prevent the thread from checking
* shared_mutables.min_timer (which requires acquiring shared_mutables.mu lock,
@@ -175,6 +294,8 @@ void grpc_timer_list_init(gpr_timespec now) {
shard->min_deadline = compute_min_deadline(shard);
g_shard_queue[i] = shard;
}
+
+ INIT_TIMER_HASH_TABLE();
}
void grpc_timer_list_shutdown(grpc_exec_ctx *exec_ctx) {
@@ -245,6 +366,10 @@ void grpc_timer_init(grpc_exec_ctx *exec_ctx, grpc_timer *timer,
timer->closure = closure;
gpr_atm deadline_atm = timer->deadline = timespec_to_atm_round_up(deadline);
+#ifndef NDEBUG
+ timer->hash_table_next = NULL;
+#endif
+
if (GRPC_TRACER_ON(grpc_timer_trace)) {
gpr_log(GPR_DEBUG, "TIMER %p: SET %" PRId64 ".%09d [%" PRIdPTR
"] now %" PRId64 ".%09d [%" PRIdPTR "] call %p[%p]",
@@ -272,6 +397,9 @@ void grpc_timer_init(grpc_exec_ctx *exec_ctx, grpc_timer *timer,
grpc_time_averaged_stats_add_sample(&shard->stats,
ts_to_dbl(gpr_time_sub(deadline, now)));
+
+ ADD_TO_HASH_TABLE(timer);
+
if (deadline_atm < shard->queue_deadline_cap) {
is_first_timer = grpc_timer_heap_add(&shard->heap, timer);
} else {
@@ -333,7 +461,10 @@ void grpc_timer_cancel(grpc_exec_ctx *exec_ctx, grpc_timer *timer) {
gpr_log(GPR_DEBUG, "TIMER %p: CANCEL pending=%s", timer,
timer->pending ? "true" : "false");
}
+
if (timer->pending) {
+ REMOVE_FROM_HASH_TABLE(timer);
+
GRPC_CLOSURE_SCHED(exec_ctx, timer->closure, GRPC_ERROR_CANCELLED);
timer->pending = false;
if (timer->heap_index == INVALID_HEAP_INDEX) {
@@ -341,6 +472,8 @@ void grpc_timer_cancel(grpc_exec_ctx *exec_ctx, grpc_timer *timer) {
} else {
grpc_timer_heap_remove(&shard->heap, timer);
}
+ } else {
+ VALIDATE_NON_PENDING_TIMER(timer);
}
gpr_mu_unlock(&shard->mu);
}
@@ -424,6 +557,7 @@ static size_t pop_timers(grpc_exec_ctx *exec_ctx, timer_shard *shard,
grpc_timer *timer;
gpr_mu_lock(&shard->mu);
while ((timer = pop_one(shard, now))) {
+ REMOVE_FROM_HASH_TABLE(timer);
GRPC_CLOSURE_SCHED(exec_ctx, timer->closure, GRPC_ERROR_REF(error));
n++;
}
diff --git a/src/core/lib/iomgr/timer_generic.h b/src/core/lib/iomgr/timer_generic.h
index 72a4ac1f107..f0597f6ea0e 100644
--- a/src/core/lib/iomgr/timer_generic.h
+++ b/src/core/lib/iomgr/timer_generic.h
@@ -29,6 +29,9 @@ struct grpc_timer {
struct grpc_timer *next;
struct grpc_timer *prev;
grpc_closure *closure;
+#ifndef NDEBUG
+ struct grpc_timer *hash_table_next;
+#endif
};
#endif /* GRPC_CORE_LIB_IOMGR_TIMER_GENERIC_H */