The patch titled Subject: Revert "selftests/mm: fix deadlock for fork after pthread_create on ARM" has been added to the -mm mm-hotfixes-unstable branch. Its filename is revert-selftests-mm-fix-deadlock-for-fork-after-pthread_create-on-arm.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Edward Liaw edliaw@google.com Subject: Revert "selftests/mm: fix deadlock for fork after pthread_create on ARM" Date: Fri, 18 Oct 2024 17:17:22 +0000

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 e142cc87ac4ec618f2ccf5f68aedcd6e28a59d9d.

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: e142cc87ac4e ("fix deadlock for fork after pthread_create on ARM") Signed-off-by: Edward 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: Andrew Morton akpm@linux-foundation.org ---

tools/testing/selftests/mm/uffd-unit-tests.c | 7 ------- 1 file changed, 7 deletions(-)

--- a/tools/testing/selftests/mm/uffd-unit-tests.c~revert-selftests-mm-fix-deadlock-for-fork-after-pthread_create-on-arm +++ a/tools/testing/selftests/mm/uffd-unit-tests.c @@ -241,9 +241,6 @@ static void *fork_event_consumer(void *d 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, b

/* 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(); _

Patches currently in -mm which might be from edliaw@google.com are

revert-selftests-mm-fix-deadlock-for-fork-after-pthread_create-on-arm.patch revert-selftests-mm-replace-atomic_bool-with-pthread_barrier_t.patch selftests-mm-fix-deadlock-for-fork-after-pthread_create-with-atomic_bool.patch