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authorSoheil Hassas Yeganeh <soheil@google.com>2020-11-01 17:08:07 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2020-11-02 12:14:19 -0800
commitafabdf3338728c3aaa9f55d127e903dcd5f4acc7 (patch)
treedf869e06afbfcd3d136588ee107ea70bb5953630 /tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c
parentmm: always have io_remap_pfn_range() set pgprot_decrypted() (diff)
downloadlinux-dev-afabdf3338728c3aaa9f55d127e903dcd5f4acc7.tar.xz
linux-dev-afabdf3338728c3aaa9f55d127e903dcd5f4acc7.zip
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. Signed-off-by: Guantao Liu <guantaol@google.com> Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Khazhismel Kumykov <khazhy@google.com> Acked-by: Willem de Bruijn <willemb@google.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Davidlohr Bueso <dave@stgolabs.net> Link: https://lkml.kernel.org/r/20201028180202.952079-2-soheil.kdev@gmail.com Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to '')
-rw-r--r--tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c95
1 files changed, 95 insertions, 0 deletions
diff --git a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c b/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c
index d979ff14775a..8f82f99f7748 100644
--- a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c
+++ b/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