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Sun, 6 Oct 2024 10:53:44 -0700 (PDT) Message-ID: Date: Sun, 6 Oct 2024 22:53:37 +0500 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 X-Rspam-User: X-Stat-Signature: gbozoaeis57s7pfj6e771oj6n63rnifw X-Rspamd-Queue-Id: ABA2918000D X-Rspamd-Server: rspam02 X-HE-Tag: 1728237243-705962 X-HE-Meta: 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 hLFwFg8z VktYvyB1rG7H9z2wtb3ZorbQYozkD7v+sahvWWKJn1wx7UoH5JQhtb6JuLZrVCx4ziLBAYHwcDpv2jfOn6SUA/5nE8VAZ9gtEwYLX0Mrv0YgI8wQvwFnqJtBpngq1lU32EnK52IatQm3LuUpNq8iS7b6iKnZMrMZEnSOs9xK8ORjbYtahpMYXHQz4eh98np3R+vdkFHbJdppqt3RN9jWL19Yoc5vi9NXTaDjtscRcjlz5UsiRPFo8oIMsWTmWxZgcowO8qev07yg1TOKomwcywSJA2ZFYAxd8UKvsolcdsvZvqOi/a/N0YNTACCGLx1TOpvJ2jjO2qQuY1Lv65diBEsnVkU5o1wDlOoyXXutkegTuJOaZve1sYUP0QJZ4ZowylObxGNlYZ4uujHoGuRI6bB/Is04jisP+qmdH43WkNXtBlPOz4Zyu9X1bkZku+HsukadU X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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