The patch titled
Subject: selftests/mm: fix deadlock for fork after pthread_create with atomic_bool
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
selftests-mm-fix-deadlock-for-fork-after-pthread_create-with-atomic_bool.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/selftests-mm-fix-deadlock-for-fork-after-pthread_create-with-atomic_bool.patch
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@xxxxxxxxxx>
Subject: selftests/mm: fix deadlock for fork after pthread_create with atomic_bool
Date: Fri, 18 Oct 2024 17:17:24 +0000
Some additional synchronization is needed on Android ARM64; we see a
deadlock with pthread_create when the parent thread races forward before
the child has a chance to start doing work.
Link: https://lkml.kernel.org/r/20241018171734.2315053-4-edliaw@xxxxxxxxxx
Fixes: cff294582798 ("selftests/mm: extend and rename uffd pagemap test")
Signed-off-by: Edward Liaw <edliaw@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
tools/testing/selftests/mm/uffd-unit-tests.c | 5 +++++
1 file changed, 5 insertions(+)
--- a/tools/testing/selftests/mm/uffd-unit-tests.c~selftests-mm-fix-deadlock-for-fork-after-pthread_create-with-atomic_bool
+++ a/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -241,6 +241,8 @@ static void *fork_event_consumer(void *d
fork_event_args *args = data;
struct uffd_msg msg = { 0 };
+ ready_for_fork = true;
+
/* Read until a full msg received */
while (uffd_read_msg(args->parent_uffd, &msg));
@@ -308,8 +310,11 @@ static int pagemap_test_fork(int uffd, b
/* Prepare a thread to resolve EVENT_FORK */
if (with_event) {
+ ready_for_fork = false;
if (pthread_create(&thread, NULL, fork_event_consumer, &args))
err("pthread_create()");
+ while (!ready_for_fork)
+ ; /* Wait for the poll_thread to start executing before forking */
}
child = fork();
_
Patches currently in -mm which might be from edliaw@xxxxxxxxxx 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
