Commit 5bb1f4c9 authored by Edward Liaw's avatar Edward Liaw Committed by Andrew Morton
Browse files

Revert "selftests/mm: fix deadlock for fork after pthread_create on ARM" 

Patch series "selftests/mm: revert pthread_barrier change"

On Android arm, pthread_create followed by a fork caused a deadlock in
the case where the fork required work to be completed by the created
thread.

The previous patches incorrectly assumed that the parent would
always initialize the pthread_barrier for the child thread.  This
reverts the change and replaces the fix for wp-fork-with-event with the
original use of atomic_bool.


This patch (of 3):

This reverts commit e142cc87.

fork_event_consumer may be called by other tests that do not initialize
the pthread_barrier, so this approach is not correct.  The subsequent
patch will revert to using atomic_bool instead.

Link: https://lkml.kernel.org/r/20241018171734.2315053-1-edliaw@google.com
Link: https://lkml.kernel.org/r/20241018171734.2315053-2-edliaw@google.com


Fixes: e142cc87 ("fix deadlock for fork after pthread_create on ARM")
Signed-off-by: default avatarEdward Liaw <edliaw@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent e8133a77

tools/testing/selftests/mm/uffd-unit-tests.c

+0 −7
Original line number Diff line number Diff line
@@ -241,9 +241,6 @@ static void *fork_event_consumer(void *data) 
	fork_event_args *args = data;

	struct uffd_msg msg = { 0 };



	/* Ready for parent thread to fork */

	pthread_barrier_wait(&ready_for_fork);



	/* Read until a full msg received */

	while (uffd_read_msg(args->parent_uffd, &msg));
@@ -311,12 +308,8 @@ static int pagemap_test_fork(int uffd, bool with_event, bool test_pin) 


	/* Prepare a thread to resolve EVENT_FORK */

	if (with_event) {

		pthread_barrier_init(&ready_for_fork, NULL, 2);

		if (pthread_create(&thread, NULL, fork_event_consumer, &args))

			err("pthread_create()");

		/* Wait for child thread to start before forking */

		pthread_barrier_wait(&ready_for_fork);

		pthread_barrier_destroy(&ready_for_fork);

	}



	child = fork();