From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C73111E6DC5; Mon, 21 Oct 2024 10:34:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729506887; cv=none; b=bK5Ugx4UahZR9dhT7sAew8oL9vssrQ1+XCiFDfPpHhLO3v4d00/vvQ0ZIdBcZweG5PgMocGdNZKM3kAgmb47Q8PcIvHcSyKRuARt2m48SmpHbEhJ0hylCa5LATLqEns70IGpQPdM+WZWA+hat+z276waJ9jnwq2/P7DzaSbZrmw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1729506887; c=relaxed/simple; bh=vBIWCqmA1lMY7N/t4uzgYAsWFZ1+IT2V2UwhY3htERE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=P4PkFh88vnaKCFtjZGbboPGgKWaXyMmmyCiT9w9D6JHOIrk1T48cmOvOnUNgGJRC6X2VEKZ8P7wxem6YTVxu3zH0BAbg224/oYzV7cfOMdS7Ia/ZzcsF8oJm8qS0F8SEo2xfbN2vh3A9DA15XpSbN0JSY5cfEt9gJY3XeQGl8Xc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=TbfRjJOt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="TbfRjJOt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1728BC4CEC3; Mon, 21 Oct 2024 10:34:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1729506887; bh=vBIWCqmA1lMY7N/t4uzgYAsWFZ1+IT2V2UwhY3htERE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TbfRjJOtha0xIAbwTUewfmZMIDLqMupIRzTiGD2zx2+tz19oiI4kQ36u7VQvIuF0e mIRSi1r8Y/TbIufVKdgQzdswY4YCZAtV3Q6pr3o7rVcYsQojGryJjBvbSFLSwI2NjQ 9yb52SQY+sfZXyqGUd9mLNnaY/vaqclvDDOEeoo0= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Edward Liaw , Lokesh Gidra , Peter Xu , Shuah Khan , Andrew Morton Subject: [PATCH 6.6 019/124] selftests/mm: replace atomic_bool with pthread_barrier_t Date: Mon, 21 Oct 2024 12:23:43 +0200 Message-ID: <20241021102257.466649133@linuxfoundation.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241021102256.706334758@linuxfoundation.org> References: <20241021102256.706334758@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Edward Liaw commit e61ef21e27e8deed8c474e9f47f4aa7bc37e138c upstream. Patch series "selftests/mm: fix deadlock after pthread_create". 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. Update the synchronization primitive to use pthread_barrier instead of atomic_bool. Apply the same fix to the wp-fork-with-event test. This patch (of 2): Swap synchronization primitive with pthread_barrier, so that stdatomic.h does not need to be included. The 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/20241003211716.371786-1-edliaw@google.com Link: https://lkml.kernel.org/r/20241003211716.371786-2-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 Signed-off-by: Greg Kroah-Hartman --- tools/testing/selftests/mm/uffd-common.c | 5 +++-- tools/testing/selftests/mm/uffd-common.h | 3 +-- tools/testing/selftests/mm/uffd-unit-tests.c | 14 ++++++++------ 3 files changed, 12 insertions(+), 10 deletions(-) --- a/tools/testing/selftests/mm/uffd-common.c +++ b/tools/testing/selftests/mm/uffd-common.c @@ -17,7 +17,7 @@ bool map_shared; bool test_uffdio_wp = true; unsigned long long *count_verify; uffd_test_ops_t *uffd_test_ops; -atomic_bool ready_for_fork; +pthread_barrier_t ready_for_fork; static int uffd_mem_fd_create(off_t mem_size, bool hugetlb) { @@ -508,7 +508,8 @@ void *uffd_poll_thread(void *arg) pollfd[1].fd = pipefd[cpu*2]; pollfd[1].events = POLLIN; - ready_for_fork = true; + /* Ready for parent thread to fork */ + pthread_barrier_wait(&ready_for_fork); for (;;) { ret = poll(pollfd, 2, -1); --- a/tools/testing/selftests/mm/uffd-common.h +++ b/tools/testing/selftests/mm/uffd-common.h @@ -33,7 +33,6 @@ #include #include #include -#include #include "../kselftest.h" #include "vm_util.h" @@ -99,7 +98,7 @@ extern bool map_shared; extern bool test_uffdio_wp; extern unsigned long long *count_verify; extern volatile bool test_uffdio_copy_eexist; -extern atomic_bool ready_for_fork; +extern pthread_barrier_t ready_for_fork; extern uffd_test_ops_t anon_uffd_test_ops; extern uffd_test_ops_t shmem_uffd_test_ops; --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -770,7 +770,7 @@ static void uffd_sigbus_test_common(bool char c; struct uffd_args args = { 0 }; - ready_for_fork = false; + pthread_barrier_init(&ready_for_fork, NULL, 2); fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); @@ -787,8 +787,9 @@ static void uffd_sigbus_test_common(bool if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) err("uffd_poll_thread create"); - while (!ready_for_fork) - ; /* Wait for the poll_thread to start executing before forking */ + /* Wait for child thread to start before forking */ + pthread_barrier_wait(&ready_for_fork); + pthread_barrier_destroy(&ready_for_fork); pid = fork(); if (pid < 0) @@ -829,7 +830,7 @@ static void uffd_events_test_common(bool char c; struct uffd_args args = { 0 }; - ready_for_fork = false; + pthread_barrier_init(&ready_for_fork, NULL, 2); fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); if (uffd_register(uffd, area_dst, nr_pages * page_size, @@ -840,8 +841,9 @@ static void uffd_events_test_common(bool if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) err("uffd_poll_thread create"); - while (!ready_for_fork) - ; /* Wait for the poll_thread to start executing before forking */ + /* Wait for child thread to start before forking */ + pthread_barrier_wait(&ready_for_fork); + pthread_barrier_destroy(&ready_for_fork); pid = fork(); if (pid < 0)