From: Andrew Morton <akpm@linux-foundation.org>
To: akpm@linux-foundation.org, dave@stgolabs.net,
edumazet@google.com, guantaol@google.com, khazhy@google.com,
linux-mm@kvack.org, mm-commits@vger.kernel.org,
soheil@google.com, torvalds@linux-foundation.org,
viro@zeniv.linux.org.uk, willemb@google.com
Subject: [patch 14/15] epoll: add a selftest for epoll timeout race
Date: Sun, 01 Nov 2020 17:08:07 -0800 [thread overview]
Message-ID: <20201102010807.RcKS-TLIz%akpm@linux-foundation.org> (raw)
In-Reply-To: <20201101170656.48abbd5e88375219f868af5e@linux-foundation.org>
From: Soheil Hassas Yeganeh <soheil@google.com>
Subject: epoll: add a selftest for epoll timeout race
Add a test case to ensure an event is observed by at least one poller when
an epoll timeout is used.
Link: https://lkml.kernel.org/r/20201028180202.952079-2-soheil.kdev@gmail.com
Signed-off-by: Guantao Liu <guantaol@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Khazhismel Kumykov <khazhy@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c | 95 ++++++++++
1 file changed, 95 insertions(+)
--- a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c~epoll-add-a-selftest-for-epoll-timeout-race
+++ a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c
@@ -3282,4 +3282,99 @@ TEST(epoll60)
close(ctx.epfd);
}
+struct epoll61_ctx {
+ int epfd;
+ int evfd;
+};
+
+static void *epoll61_write_eventfd(void *ctx_)
+{
+ struct epoll61_ctx *ctx = ctx_;
+ int64_t l = 1;
+
+ usleep(10950);
+ write(ctx->evfd, &l, sizeof(l));
+ return NULL;
+}
+
+static void *epoll61_epoll_with_timeout(void *ctx_)
+{
+ struct epoll61_ctx *ctx = ctx_;
+ struct epoll_event events[1];
+ int n;
+
+ n = epoll_wait(ctx->epfd, events, 1, 11);
+ /*
+ * If epoll returned the eventfd, write on the eventfd to wake up the
+ * blocking poller.
+ */
+ if (n == 1) {
+ int64_t l = 1;
+
+ write(ctx->evfd, &l, sizeof(l));
+ }
+ return NULL;
+}
+
+static void *epoll61_blocking_epoll(void *ctx_)
+{
+ struct epoll61_ctx *ctx = ctx_;
+ struct epoll_event events[1];
+
+ epoll_wait(ctx->epfd, events, 1, -1);
+ return NULL;
+}
+
+TEST(epoll61)
+{
+ struct epoll61_ctx ctx;
+ struct epoll_event ev;
+ int i, r;
+
+ ctx.epfd = epoll_create1(0);
+ ASSERT_GE(ctx.epfd, 0);
+ ctx.evfd = eventfd(0, EFD_NONBLOCK);
+ ASSERT_GE(ctx.evfd, 0);
+
+ ev.events = EPOLLIN | EPOLLET | EPOLLERR | EPOLLHUP;
+ ev.data.ptr = NULL;
+ r = epoll_ctl(ctx.epfd, EPOLL_CTL_ADD, ctx.evfd, &ev);
+ ASSERT_EQ(r, 0);
+
+ /*
+ * We are testing a race. Repeat the test case 1000 times to make it
+ * more likely to fail in case of a bug.
+ */
+ for (i = 0; i < 1000; i++) {
+ pthread_t threads[3];
+ int n;
+
+ /*
+ * Start 3 threads:
+ * Thread 1 sleeps for 10.9ms and writes to the evenfd.
+ * Thread 2 calls epoll with a timeout of 11ms.
+ * Thread 3 calls epoll with a timeout of -1.
+ *
+ * The eventfd write by Thread 1 should either wakeup Thread 2
+ * or Thread 3. If it wakes up Thread 2, Thread 2 writes on the
+ * eventfd to wake up Thread 3.
+ *
+ * If no events are missed, all three threads should eventually
+ * be joinable.
+ */
+ ASSERT_EQ(pthread_create(&threads[0], NULL,
+ epoll61_write_eventfd, &ctx), 0);
+ ASSERT_EQ(pthread_create(&threads[1], NULL,
+ epoll61_epoll_with_timeout, &ctx), 0);
+ ASSERT_EQ(pthread_create(&threads[2], NULL,
+ epoll61_blocking_epoll, &ctx), 0);
+
+ for (n = 0; n < ARRAY_SIZE(threads); ++n)
+ ASSERT_EQ(pthread_join(threads[n], NULL), 0);
+ }
+
+ close(ctx.epfd);
+ close(ctx.evfd);
+}
+
TEST_HARNESS_MAIN
_
next prev parent reply other threads:[~2020-11-02 1:08 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-02 1:06 incoming Andrew Morton
2020-11-02 1:07 ` [patch 01/15] mm/mremap_pages: fix static key devmap_managed_key updates Andrew Morton
2020-11-02 1:07 ` [patch 02/15] hugetlb_cgroup: fix reservation accounting Andrew Morton
2020-11-02 1:07 ` [patch 03/15] mm: memcontrol: correct the NR_ANON_THPS counter of hierarchical memcg Andrew Morton
2020-11-02 1:07 ` [patch 04/15] mm: memcg: link page counters to root if use_hierarchy is false Andrew Morton
2020-11-02 1:07 ` [patch 05/15] kasan: adopt KUNIT tests to SW_TAGS mode Andrew Morton
2020-11-02 1:07 ` [patch 06/15] mm: mempolicy: fix potential pte_unmap_unlock pte error Andrew Morton
2020-11-02 1:07 ` [patch 07/15] ptrace: fix task_join_group_stop() for the case when current is traced Andrew Morton
2020-11-02 1:07 ` [patch 08/15] lib/crc32test: remove extra local_irq_disable/enable Andrew Morton
2020-11-02 1:07 ` [patch 09/15] mm/truncate.c: make __invalidate_mapping_pages() static Andrew Morton
2020-11-02 1:07 ` [patch 10/15] kthread_worker: prevent queuing delayed work from timer_fn when it is being canceled Andrew Morton
2020-11-02 1:07 ` [patch 11/15] mm, oom: keep oom_adj under or at upper limit when printing Andrew Morton
2020-11-02 1:08 ` [patch 12/15] mm: always have io_remap_pfn_range() set pgprot_decrypted() Andrew Morton
2020-11-02 1:08 ` [patch 13/15] epoll: check ep_events_available() upon timeout Andrew Morton
2020-11-02 17:08 ` Linus Torvalds
2020-11-02 17:48 ` Soheil Hassas Yeganeh
2020-11-02 18:51 ` Linus Torvalds
2020-11-02 19:38 ` Linus Torvalds
2020-11-02 19:54 ` Soheil Hassas Yeganeh
2020-11-02 20:12 ` Linus Torvalds
2020-11-02 1:08 ` Andrew Morton [this message]
2020-11-02 1:08 ` [patch 15/15] kernel/hung_task.c: make type annotations consistent Andrew Morton
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