From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + kselftest-introduce-new-epoll-test-case.patch added to -mm tree Date: Wed, 19 Feb 2020 15:31:15 -0800 Message-ID: <20200219233115.Q7o7I%akpm@linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from mail.kernel.org ([198.145.29.99]:44458 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726691AbgBSXbQ (ORCPT ); Wed, 19 Feb 2020 18:31:16 -0500 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org, max@arangodb.com, kuba@kernel.org, jbaron@akamai.com, dbueso@suse.de, chris.kohlhoff@clearpool.io, rpenyaev@suse.de The patch titled Subject: kselftest: introduce new epoll test case has been added to the -mm tree. Its filename is kselftest-introduce-new-epoll-test-case.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/kselftest-introduce-new-epoll-test-case.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/kselftest-introduce-new-epoll-test-case.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Roman Penyaev Subject: kselftest: introduce new epoll test case This testcase repeats epollbug.c from the bug: https://bugzilla.kernel.org/show_bug.cgi?id=205933 What it tests? It tests the race between epoll_ctl() and epoll_wait(). New event mask passed to epoll_ctl() triggers wake up, which can be missed because of the bug described in the link. Reproduction is 100%, so easy to fix. Kudos, Max, for wonderful test case. Link: http://lkml.kernel.org/r/20200214170211.561524-2-rpenyaev@suse.de Signed-off-by: Roman Penyaev Cc: Max Neunhoeffer Cc: Jakub Kicinski Cc: Christopher Kohlhoff Cc: Davidlohr Bueso Cc: Jason Baron Signed-off-by: Andrew Morton --- tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c | 67 +++++++++- 1 file changed, 66 insertions(+), 1 deletion(-) --- a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c~kselftest-introduce-new-epoll-test-case +++ a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c @@ -7,13 +7,14 @@ #include #include #include +#include #include "../../kselftest_harness.h" struct epoll_mtcontext { int efd[3]; int sfd[4]; - int count; + volatile int count; pthread_t main; pthread_t waiter; @@ -3071,4 +3072,68 @@ TEST(epoll58) close(ctx.sfd[3]); } +static void *epoll59_thread(void *ctx_) +{ + struct epoll_mtcontext *ctx = ctx_; + struct epoll_event e; + int i; + + for (i = 0; i < 100000; i++) { + while (ctx->count == 0) + ; + + e.events = EPOLLIN | EPOLLERR | EPOLLET; + epoll_ctl(ctx->efd[0], EPOLL_CTL_MOD, ctx->sfd[0], &e); + ctx->count = 0; + } + + return NULL; +} + +/* + * t0 + * (p) \ + * e0 + * (et) / + * e0 + * + * Based on https://bugzilla.kernel.org/show_bug.cgi?id=205933 + */ +TEST(epoll59) +{ + pthread_t emitter; + struct pollfd pfd; + struct epoll_event e; + struct epoll_mtcontext ctx = { 0 }; + int i, ret; + + signal(SIGUSR1, signal_handler); + + ctx.efd[0] = epoll_create1(0); + ASSERT_GE(ctx.efd[0], 0); + + ctx.sfd[0] = eventfd(1, 0); + ASSERT_GE(ctx.sfd[0], 0); + + e.events = EPOLLIN | EPOLLERR | EPOLLET; + ASSERT_EQ(epoll_ctl(ctx.efd[0], EPOLL_CTL_ADD, ctx.sfd[0], &e), 0); + + ASSERT_EQ(pthread_create(&emitter, NULL, epoll59_thread, &ctx), 0); + + for (i = 0; i < 100000; i++) { + ret = epoll_wait(ctx.efd[0], &e, 1, 1000); + ASSERT_GT(ret, 0); + + while (ctx.count != 0) + ; + ctx.count = 1; + } + if (pthread_tryjoin_np(emitter, NULL) < 0) { + pthread_kill(emitter, SIGUSR1); + pthread_join(emitter, NULL); + } + close(ctx.efd[0]); + close(ctx.sfd[0]); +} + TEST_HARNESS_MAIN _ Patches currently in -mm which might be from rpenyaev@suse.de are epoll-fix-possible-lost-wakeup-on-epoll_ctl-path.patch kselftest-introduce-new-epoll-test-case.patch