From: Edward Liaw <edliaw@xxxxxxxxxx> commit e142cc87ac4ec618f2ccf5f68aedcd6e28a59d9d upstream. On Android with arm, there is some synchronization needed to avoid a deadlock when forking after pthread_create. Link: https://lkml.kernel.org/r/20241003211716.371786-3-edliaw@xxxxxxxxxx Fixes: cff294582798 ("selftests/mm: extend and rename uffd pagemap test") Signed-off-by: Edward Liaw <edliaw@xxxxxxxxxx> Cc: Lokesh Gidra <lokeshgidra@xxxxxxxxxx> Cc: Peter Xu <peterx@xxxxxxxxxx> Cc: Shuah Khan <shuah@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- tools/testing/selftests/mm/uffd-unit-tests.c | 7 +++++++ 1 file changed, 7 insertions(+) --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -237,6 +237,9 @@ 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)); @@ -304,8 +307,12 @@ 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 stable-queue which might be from edliaw@xxxxxxxxxx are queue-6.6/selftests-mm-replace-atomic_bool-with-pthread_barrier_t.patch queue-6.6/selftests-mm-fix-deadlock-for-fork-after-pthread_create-on-arm.patch
