Commit fbf4dec7 authored by Nysal Jan K.A's avatar Nysal Jan K.A Committed by Shuah Khan
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selftests/futex: Order calls to futex_lock_pi 



Observed occassional failures in the futex_wait_timeout test:

ok 1 futex_wait relative succeeds
ok 2 futex_wait_bitset realtime succeeds
ok 3 futex_wait_bitset monotonic succeeds
ok 4 futex_wait_requeue_pi realtime succeeds
ok 5 futex_wait_requeue_pi monotonic succeeds
not ok 6 futex_lock_pi realtime returned 0
......

The test expects the child thread to complete some steps before
the parent thread gets to run. There is an implicit expectation
of the order of invocation of futex_lock_pi between the child thread
and the parent thread. Make this order explicit. If the order is
not met, the futex_lock_pi call in the parent thread succeeds and
will not timeout.

Fixes: f4addd54 ("selftests: futex: Expand timeout test")
Signed-off-by: default avatarNysal Jan K.A <nysal@linux.ibm.com>
Signed-off-by: default avatarShuah Khan <skhan@linuxfoundation.org>
parent 888c72d5

tools/testing/selftests/futex/functional/futex_wait_timeout.c

+7 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ 


static long timeout_ns = 100000;	/* 100us default timeout */

static futex_t futex_pi;

static pthread_barrier_t barrier;



void usage(char *prog)

{
@@ -48,6 +49,8 @@ void *get_pi_lock(void *arg) 
	if (ret != 0)

		error("futex_lock_pi failed\n", ret);



	pthread_barrier_wait(&barrier);



	/* Blocks forever */

	ret = futex_wait(&lock, 0, NULL, 0);

	error("futex_wait failed\n", ret);
@@ -130,6 +133,7 @@ int main(int argc, char *argv[]) 
	       basename(argv[0]));

	ksft_print_msg("\tArguments: timeout=%ldns\n", timeout_ns);



	pthread_barrier_init(&barrier, NULL, 2);

	pthread_create(&thread, NULL, get_pi_lock, NULL);



	/* initialize relative timeout */
@@ -163,6 +167,9 @@ int main(int argc, char *argv[]) 
	res = futex_wait_requeue_pi(&f1, f1, &futex_pi, &to, 0);

	test_timeout(res, &ret, "futex_wait_requeue_pi monotonic", ETIMEDOUT);



	/* Wait until the other thread calls futex_lock_pi() */

	pthread_barrier_wait(&barrier);

	pthread_barrier_destroy(&barrier);

	/*

	 * FUTEX_LOCK_PI with CLOCK_REALTIME

	 * Due to historical reasons, FUTEX_LOCK_PI supports only realtime