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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Andrew Morton , Shuah Khan , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Jann Horn References: <20240325194100.775052-1-edliaw@google.com> Content-Language: en-US From: Muhammad Usama Anjum In-Reply-To: <20240325194100.775052-1-edliaw@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 1574640007 X-Stat-Signature: a94ik461arxxj1ok1yag83ma7ysoqhqm X-Rspam-User: X-HE-Tag: 1711742043-608045 X-HE-Meta: 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 xJ8lf9ZT 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 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 3/26/24 12:40 AM, Edward Liaw wrote: > Following issue was observed while running the uffd-unit-tests selftest > on ARM devices. On x86_64 no issues were detected: > > pthread_create followed by fork caused deadlock in certain cases > wherein fork required some work to be completed by the created thread. > Used synchronization to ensure that created thread's start function has > started before invoking fork. > > Signed-off-by: Lokesh Gidra > [edliaw: Refactored to use atomic_bool] > Signed-off-by: Edward Liaw Reviewed-by: Muhammad Usama Anjum > --- > > v2: restored accidentally removed uffd_test_case_ops when merging > v3: fixed commit subject to use selftests/mm prefix > > tools/testing/selftests/mm/uffd-common.c | 3 +++ > tools/testing/selftests/mm/uffd-common.h | 2 ++ > tools/testing/selftests/mm/uffd-unit-tests.c | 10 ++++++++++ > 3 files changed, 15 insertions(+) > > diff --git a/tools/testing/selftests/mm/uffd-common.c b/tools/testing/selftests/mm/uffd-common.c > index b0ac0ec2356d..7ad6ba660c7d 100644 > --- a/tools/testing/selftests/mm/uffd-common.c > +++ b/tools/testing/selftests/mm/uffd-common.c > @@ -18,6 +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; > > static int uffd_mem_fd_create(off_t mem_size, bool hugetlb) > { > @@ -518,6 +519,8 @@ void *uffd_poll_thread(void *arg) > pollfd[1].fd = pipefd[cpu*2]; > pollfd[1].events = POLLIN; > > + ready_for_fork = true; > + > for (;;) { > ret = poll(pollfd, 2, -1); > if (ret <= 0) { > diff --git a/tools/testing/selftests/mm/uffd-common.h b/tools/testing/selftests/mm/uffd-common.h > index cb055282c89c..cc5629c3d2aa 100644 > --- a/tools/testing/selftests/mm/uffd-common.h > +++ b/tools/testing/selftests/mm/uffd-common.h > @@ -32,6 +32,7 @@ > #include > #include > #include > +#include > > #include "../kselftest.h" > #include "vm_util.h" > @@ -103,6 +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 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 2b9f8cc52639..4a48dc617c6b 100644 > --- a/tools/testing/selftests/mm/uffd-unit-tests.c > +++ b/tools/testing/selftests/mm/uffd-unit-tests.c > @@ -775,6 +775,8 @@ static void uffd_sigbus_test_common(bool wp) > char c; > struct uffd_args args = { 0 }; > > + ready_for_fork = false; > + > fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); > > if (uffd_register(uffd, area_dst, nr_pages * page_size, > @@ -790,6 +792,9 @@ 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 */ > + > pid = fork(); > if (pid < 0) > err("fork"); > @@ -829,6 +834,8 @@ static void uffd_events_test_common(bool wp) > char c; > struct uffd_args args = { 0 }; > > + ready_for_fork = false; > + > fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK); > if (uffd_register(uffd, area_dst, nr_pages * page_size, > true, wp, false)) > @@ -838,6 +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 */ > + > pid = fork(); > if (pid < 0) > err("fork"); > -- > 2.44.0.396.g6e790dbe36-goog > > -- BR, Muhammad Usama Anjum