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Merge "Fix race condition in timer disarm/delete."

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This commit is contained in:
Christopher Ferris 2014-10-22 20:33:05 +00:00 committed by Gerrit Code Review
commit efd2ec8fbd
2 changed files with 97 additions and 18 deletions
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20
libc/bionic/posix_timers.cpp
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@ -62,6 +62,7 @@ struct PosixTimer {
pthread_t callback_thread;
void (*callback)(sigval_t);
sigval_t callback_argument;
volatile bool armed;
};
static __kernel_timer_t to_kernel_timer_id(timer_t timer) {
@ -83,7 +84,7 @@ static void* __timer_thread_start(void* arg) {
continue;
}
if (si.si_code == SI_TIMER) {
if (si.si_code == SI_TIMER && timer->armed) {
// This signal was sent because a timer fired, so call the callback.
timer->callback(timer->callback_argument);
} else if (si.si_code == SI_TKILL) {
@ -95,6 +96,9 @@ static void* __timer_thread_start(void* arg) {
}
static void __timer_thread_stop(PosixTimer* timer) {
// Immediately mark the timer as disarmed so even if some events
// continue to happen, the callback won't be called.
timer->armed = false;
pthread_kill(timer->callback_thread, TIMER_SIGNAL);
}
@ -121,6 +125,7 @@ int timer_create(clockid_t clock_id, sigevent* evp, timer_t* timer_id) {
// Otherwise, this must be SIGEV_THREAD timer...
timer->callback = evp->sigev_notify_function;
timer->callback_argument = evp->sigev_value;
timer->armed = false;
// Check arguments that the kernel doesn't care about but we do.
if (timer->callback == NULL) {
@ -200,7 +205,18 @@ int timer_gettime(timer_t id, itimerspec* ts) {
// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html
int timer_settime(timer_t id, int flags, const itimerspec* ts, itimerspec* ots) {
return __timer_settime(to_kernel_timer_id(id), flags, ts, ots);
PosixTimer* timer= reinterpret_cast<PosixTimer*>(id);
int rc = __timer_settime(timer->kernel_timer_id, flags, ts, ots);
if (rc == 0) {
// Mark the timer as either being armed or disarmed. This avoids the
// callback being called after the disarm for SIGEV_THREAD timers only.
if (ts->it_value.tv_sec != 0 || ts->it_value.tv_nsec != 0) {
timer->armed = true;
} else {
timer->armed = false;
}
}
return rc;
}
// http://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_getoverrun.html

95
tests/time_test.cpp
View File

@ -206,24 +206,46 @@ struct Counter {
volatile int value;
timer_t timer_id;
sigevent_t se;
bool timer_valid;
Counter(void (*fn)(sigval_t)) : value(0) {
Counter(void (*fn)(sigval_t)) : value(0), timer_valid(false) {
memset(&se, 0, sizeof(se));
se.sigev_notify = SIGEV_THREAD;
se.sigev_notify_function = fn;
se.sigev_value.sival_ptr = this;
Create();
}
void Create() {
ASSERT_FALSE(timer_valid);
ASSERT_EQ(0, timer_create(CLOCK_REALTIME, &se, &timer_id));
timer_valid = true;
}
void DeleteTimer() {
ASSERT_TRUE(timer_valid);
ASSERT_EQ(0, timer_delete(timer_id));
timer_valid = false;
}
~Counter() {
if (timer_delete(timer_id) != 0) {
abort();
if (timer_valid) {
DeleteTimer();
}
}
void SetTime(time_t value_s, time_t value_ns, time_t interval_s, time_t interval_ns) {
::SetTime(timer_id, value_s, value_ns, interval_s, interval_ns);
}
bool ValueUpdated() {
volatile int current_value = value;
time_t start = time(NULL);
while (current_value == value && (time(NULL) - start) < 5) {
}
return current_value != value;
}
static void CountNotifyFunction(sigval_t value) {
Counter* cd = reinterpret_cast<Counter*>(value.sival_ptr);
++cd->value;
@ -234,17 +256,17 @@ struct Counter {
++cd->value;
// Setting the initial expiration time to 0 disarms the timer.
SetTime(cd->timer_id, 0, 0, 1, 0);
cd->SetTime(0, 0, 1, 0);
}
};
TEST(time, timer_settime_0) {
Counter counter(Counter::CountAndDisarmNotifyFunction);
counter.Create();
ASSERT_TRUE(counter.timer_valid);
ASSERT_EQ(0, counter.value);
SetTime(counter.timer_id, 0, 1, 1, 0);
counter.SetTime(0, 1, 1, 0);
usleep(500000);
// The count should just be 1 because we disarmed the timer the first time it fired.
@ -253,15 +275,14 @@ TEST(time, timer_settime_0) {
TEST(time, timer_settime_repeats) {
Counter counter(Counter::CountNotifyFunction);
counter.Create();
ASSERT_TRUE(counter.timer_valid);
ASSERT_EQ(0, counter.value);
SetTime(counter.timer_id, 0, 1, 0, 10);
usleep(500000);
// The count should just be > 1 because we let the timer repeat.
ASSERT_GT(counter.value, 1);
counter.SetTime(0, 1, 0, 10);
ASSERT_TRUE(counter.ValueUpdated());
ASSERT_TRUE(counter.ValueUpdated());
ASSERT_TRUE(counter.ValueUpdated());
}
static int timer_create_NULL_signal_handler_invocation_count = 0;
@ -321,17 +342,17 @@ TEST(time, timer_delete_multiple) {
TEST(time, timer_create_multiple) {
Counter counter1(Counter::CountNotifyFunction);
counter1.Create();
ASSERT_TRUE(counter1.timer_valid);
Counter counter2(Counter::CountNotifyFunction);
counter2.Create();
ASSERT_TRUE(counter2.timer_valid);
Counter counter3(Counter::CountNotifyFunction);
counter3.Create();
ASSERT_TRUE(counter3.timer_valid);
ASSERT_EQ(0, counter1.value);
ASSERT_EQ(0, counter2.value);
ASSERT_EQ(0, counter3.value);
SetTime(counter2.timer_id, 0, 1, 0, 0);
counter2.SetTime(0, 1, 0, 0);
usleep(500000);
EXPECT_EQ(0, counter1.value);
@ -425,3 +446,45 @@ TEST(time, clock_nanosleep) {
timespec out;
ASSERT_EQ(EINVAL, clock_nanosleep(-1, 0, &in, &out));
}
// Test to verify that disarming a repeatable timer disables the
// callbacks.
TEST(time, timer_disarm_terminates) {
Counter counter(Counter::CountNotifyFunction);
ASSERT_TRUE(counter.timer_valid);
ASSERT_EQ(0, counter.value);
counter.SetTime(0, 1, 0, 1);
ASSERT_TRUE(counter.ValueUpdated());
ASSERT_TRUE(counter.ValueUpdated());
ASSERT_TRUE(counter.ValueUpdated());
counter.SetTime(0, 0, 1, 0);
volatile int value = counter.value;
usleep(500000);
// Verify the counter has not been incremented.
ASSERT_EQ(value, counter.value);
}
// Test to verify that deleting a repeatable timer disables the
// callbacks.
TEST(time, timer_delete_terminates) {
Counter counter(Counter::CountNotifyFunction);
ASSERT_TRUE(counter.timer_valid);
ASSERT_EQ(0, counter.value);
counter.SetTime(0, 1, 0, 1);
ASSERT_TRUE(counter.ValueUpdated());
ASSERT_TRUE(counter.ValueUpdated());
ASSERT_TRUE(counter.ValueUpdated());
counter.DeleteTimer();
volatile int value = counter.value;
usleep(500000);
// Verify the counter has not been incremented.
ASSERT_EQ(value, counter.value);
}