From e142cc87ac4ec618f2ccf5f68aedcd6e28a59d9d Mon Sep 17 00:00:00 2001 From: Edward Liaw Date: Thu, 3 Oct 2024 21:17:11 +0000 Subject: selftests/mm: fix deadlock for fork after pthread_create on ARM 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@google.com Fixes: cff294582798 ("selftests/mm: extend and rename uffd pagemap test") Signed-off-by: Edward Liaw Cc: Lokesh Gidra Cc: Peter Xu Cc: Shuah Khan Cc: Signed-off-by: Andrew Morton --- tools/testing/selftests/mm/uffd-unit-tests.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'tools') diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c index 3db2296ac631..c8a3b1c7edff 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -241,6 +241,9 @@ 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)); @@ -308,8 +311,12 @@ 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(); -- cgit