Fix deadlock in timer_delete.
If the callback function for a timer did a timer_delete, the function
would never return. The problem was that the timer_delete function would try
to wait until the timer thread has finished. Waiting for yourself to finish
doesn't work very well.
Bug: 13397340
Change-Id: Ica123a5bafbc8660c8a4a909e5c2dead55ca429d
diff --git a/libc/bionic/posix_timers.cpp b/libc/bionic/posix_timers.cpp
index ffe213c..e9190b2 100644
--- a/libc/bionic/posix_timers.cpp
+++ b/libc/bionic/posix_timers.cpp
@@ -100,11 +100,14 @@
static void __timer_thread_stop(PosixTimer* timer) {
pthread_kill(timer->callback_thread, TIMER_SIGNAL);
- // We can't pthread_join because POSIX says "the threads created in response to a timer
- // expiration are created detached, or in an unspecified way if the thread attribute's
- // detachstate is PTHREAD_CREATE_JOINABLE".
- while (timer->exiting == 0) {
- __futex_wait(&timer->exiting, 0, NULL);
+ // If this is being called from within the callback thread, do nothing else.
+ if (pthread_self() != timer->callback_thread) {
+ // We can't pthread_join because POSIX says "the threads created in response to a timer
+ // expiration are created detached, or in an unspecified way if the thread attribute's
+ // detachstate is PTHREAD_CREATE_JOINABLE".
+ while (timer->exiting == 0) {
+ __futex_wait(&timer->exiting, 0, NULL);
+ }
}
}
diff --git a/tests/time_test.cpp b/tests/time_test.cpp
index af6ae85..26b7775 100644
--- a/tests/time_test.cpp
+++ b/tests/time_test.cpp
@@ -341,3 +341,49 @@
EXPECT_EQ(1, counter2.value);
EXPECT_EQ(0, counter3.value);
}
+
+struct TimerDeleteData {
+ timer_t timer_id;
+ pthread_t thread_id;
+ volatile bool complete;
+};
+
+static void TimerDeleteCallback(sigval_t value) {
+ TimerDeleteData* tdd = reinterpret_cast<TimerDeleteData*>(value.sival_ptr);
+
+ tdd->thread_id = pthread_self();
+ timer_delete(tdd->timer_id);
+ tdd->complete = true;
+}
+
+TEST(time, timer_delete_from_timer_thread) {
+ TimerDeleteData tdd;
+ sigevent_t se;
+
+ memset(&se, 0, sizeof(se));
+ se.sigev_notify = SIGEV_THREAD;
+ se.sigev_notify_function = TimerDeleteCallback;
+ se.sigev_value.sival_ptr = &tdd;
+
+ tdd.complete = false;
+ ASSERT_EQ(0, timer_create(CLOCK_REALTIME, &se, &tdd.timer_id));
+
+ itimerspec ts;
+ ts.it_value.tv_sec = 0;
+ ts.it_value.tv_nsec = 100;
+ ts.it_interval.tv_sec = 0;
+ ts.it_interval.tv_nsec = 0;
+ ASSERT_EQ(0, timer_settime(tdd.timer_id, TIMER_ABSTIME, &ts, NULL));
+
+ time_t cur_time = time(NULL);
+ while (!tdd.complete && (time(NULL) - cur_time) < 5);
+ ASSERT_TRUE(tdd.complete);
+
+#if defined(__BIONIC__)
+ // Since bionic timers are implemented by creating a thread to handle the
+ // callback, verify that the thread actually completes.
+ cur_time = time(NULL);
+ while (pthread_detach(tdd.thread_id) != ESRCH && (time(NULL) - cur_time) < 5);
+ ASSERT_EQ(ESRCH, pthread_detach(tdd.thread_id));
+#endif
+}