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bh=XTnVDAmnVGyJDi/jgM2YrR/nJtg9MBkwlu2KSem8Wh8=; b=BGm0xk5L8zLrUsy/0LV1PVbAmRioiYqSRTlw/Wi6YPZNLWkkShyWTgiKCUvGHGy7Pqdsnl+CC2B7Tr7g6V4QR8HTEsKwD9W0LapL/JTYYCzRVGjDlY4dxc0wf5XY1aLLThIvHsHPtFt9bgvRCYYS+inS7EMEW/pCYVaeE6N3gUg= ARC-Authentication-Results: i=1; mx.zohomail.com; dkim=pass header.i=collabora.com; spf=pass smtp.mailfrom=Usama.Anjum@collabora.com; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1728237226; s=zohomail; d=collabora.com; i=Usama.Anjum@collabora.com; h=Message-ID:Date:Date:MIME-Version:Cc:Cc:Subject:Subject:To:To:References:From:From:In-Reply-To:Content-Type:Content-Transfer-Encoding:Message-Id:Reply-To; bh=XTnVDAmnVGyJDi/jgM2YrR/nJtg9MBkwlu2KSem8Wh8=; b=XmNK0Pm8739o8mTtjI9Y4zO2oEnhKe5Q9DSyaV1eO+QUJiwQ5KNJZ2a3NdDeGJx8 133V1k99tF0WW/CeJ0ZCAQm5PI6r1D/xi+g3iIPDSdZlLKXM8sW2skQc6P1MjHOfyWl QHrnHx2oIoxQ2jectMOycWXUkpVGn1W/A+DhZKwQ= Received: by mx.zohomail.com with SMTPS id 1728237224277627.9130859707182; Sun, 6 Oct 2024 10:53:44 -0700 (PDT) Message-ID: Date: Sun, 6 Oct 2024 22:53:37 +0500 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Cc: Usama.Anjum@collabora.com, linux-kernel@vger.kernel.org, kernel-team@android.com, linux-mm@kvack.org Subject: Re: [PATCH 1/2] selftests/mm: replace atomic_bool with pthread_barrier_t To: Edward Liaw , linux-kselftest@vger.kernel.org, Andrew Morton , Shuah Khan , Lokesh Gidra , Peter Xu References: <20241003211716.371786-1-edliaw@google.com> <20241003211716.371786-2-edliaw@google.com> Content-Language: en-US From: Muhammad Usama Anjum In-Reply-To: <20241003211716.371786-2-edliaw@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-ZohoMailClient: External On 10/4/24 2:17 AM, Edward Liaw wrote: > Swaps 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. > > Fixes: 8c864371b2a1 ("selftests/mm: fix ARM related issue with fork after > pthread_create") > Signed-off-by: Edward Liaw Reviewed-by: Muhammad Usama Anjum > --- > 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(-) > > diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c > index 717539eddf98..852e7281026e 100644 > --- a/tools/testing/selftests/mm/uffd-common.c > +++ b/tools/testing/selftests/mm/uffd-common.c > @@ -18,7 +18,7 @@ bool test_uffdio_wp = true; > unsigned long long *count_verify; > uffd_test_ops_t *uffd_test_ops; > uffd_test_case_ops_t *uffd_test_case_ops; > -atomic_bool ready_for_fork; > +pthread_barrier_t ready_for_fork; > > static int uffd_mem_fd_create(off_t mem_size, bool hugetlb) > { > @@ -519,7 +519,8 @@ 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); > diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h > index a70ae10b5f62..3e6228d8e0dc 100644 > --- 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" > @@ -105,7 +104,7 @@ 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; > diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c > index b3d21eed203d..3db2296ac631 100644 > --- a/tools/testing/selftests/mm/uffd-unit-tests.c > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c > @@ -774,7 +774,7 @@ static void uffd_sigbus_test_common(bool wp) > 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); > > @@ -791,8 +791,9 @@ static void uffd_sigbus_test_common(bool wp) > 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) > @@ -833,7 +834,7 @@ static void uffd_events_test_common(bool wp) > 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, > @@ -844,8 +845,9 @@ static void uffd_events_test_common(bool wp) > 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) -- BR, Muhammad Usama Anjum