Commit 1e3b918d authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
Browse files

kselftest: introduce new epoll test case 

Patch series "fs/epoll: restore user-visible behavior upon event ready".

This series tries to address a change in user visible behavior, reported
in https://bugzilla.kernel.org/show_bug.cgi?id=208943.

Epoll does not report an event to all the threads running epoll_wait()
on the same epoll descriptor. Unsurprisingly, this was bisected back to
339ddb53 (fs/epoll: remove unnecessary wakeups of nested epoll), which
has had various problems in the past, beyond only nested epoll usage.

This patch (of 2):

This incorporates the testcase originally reported in:

     https://bugzilla.kernel.org/show_bug.cgi?id=208943

Which ensures an event is reported to all threads blocked on the same
epoll descriptor, otherwise only a single thread will receive the wakeup
once the event become ready.

Link: https://lkml.kernel.org/r/20210405231025.33829-1-dave@stgolabs.net
Link: https://lkml.kernel.org/r/20210405231025.33829-2-dave@stgolabs.net


Signed-off-by: default avatarDavidlohr Bueso <dbueso@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Roman Penyaev <rpenyaev@suse.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7e6cdd7f

tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c

+44 −0
Original line number Diff line number Diff line
@@ -3449,4 +3449,48 @@ TEST(epoll63) 
	close(sfd[1]);

}



/*

 *        t0    t1

 *     (ew) \  / (ew)

 *           e0

 *            | (lt)

 *           s0

 */

TEST(epoll64)

{

	pthread_t waiter[2];

	struct epoll_event e;

	struct epoll_mtcontext ctx = { 0 };



	signal(SIGUSR1, signal_handler);



	ASSERT_EQ(socketpair(AF_UNIX, SOCK_STREAM, 0, ctx.sfd), 0);



	ctx.efd[0] = epoll_create(1);

	ASSERT_GE(ctx.efd[0], 0);



	e.events = EPOLLIN;

	ASSERT_EQ(epoll_ctl(ctx.efd[0], EPOLL_CTL_ADD, ctx.sfd[0], &e), 0);



	/*

	 * main will act as the emitter once both waiter threads are

	 * blocked and expects to both be awoken upon the ready event.

	 */

	ctx.main = pthread_self();

	ASSERT_EQ(pthread_create(&waiter[0], NULL, waiter_entry1a, &ctx), 0);

	ASSERT_EQ(pthread_create(&waiter[1], NULL, waiter_entry1a, &ctx), 0);



	usleep(100000);

	ASSERT_EQ(write(ctx.sfd[1], "w", 1), 1);



	ASSERT_EQ(pthread_join(waiter[0], NULL), 0);

	ASSERT_EQ(pthread_join(waiter[1], NULL), 0);



	EXPECT_EQ(ctx.count, 2);



	close(ctx.efd[0]);

	close(ctx.sfd[0]);

	close(ctx.sfd[1]);

}



TEST_HARNESS_MAIN