linux-kernel - [PATCH 1/3] Revert "selftests/mm: fix deadlock for fork after pthread

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Message-ID: <20241018171734.2315053-2-edliaw@google.com>
Date: Fri, 18 Oct 2024 17:17:22 +0000
From: Edward Liaw <edliaw@...gle.com>
To: linux-kselftest@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	Shuah Khan <shuah@...nel.org>, Edward Liaw <edliaw@...gle.com>, Peter Xu <peterx@...hat.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com, linux-mm@...ck.org, 
	Ryan Roberts <ryan.roberts@....com>
Subject: [PATCH 1/3] Revert "selftests/mm: fix deadlock for fork after
 pthread_create on ARM"

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.

Fixes: e142cc87ac4e ("fix deadlock for fork after pthread_create on ARM")
CC: Ryan Roberts <ryan.roberts@....com>
Signed-off-by: Edward Liaw <edliaw@...gle.com>
---
 tools/testing/selftests/mm/uffd-unit-tests.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c
index c8a3b1c7edff..3db2296ac631 100644
--- a/tools/testing/selftests/mm/uffd-unit-tests.c
+++ b/tools/testing/selftests/mm/uffd-unit-tests.c
@@ -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();
-- 
2.47.0.105.g07ac214952-goog