From: Nam Cao <namcao@linutronix.de>
Date: Tue, 2 Jun 2026 17:51:45 +0000 (+0200)
Subject: selftests/eventpoll: Add test for multiple waiters
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=827382c088e9ac18a9e05c0a238a2ff919bc4755;p=thirdparty%2Flinux.git

selftests/eventpoll: Add test for multiple waiters

Add a test whichs creates 64 threads who all epoll_wait() on the same
eventpoll. The source eventfd is written but never read, therefore all the
threads should always see an EPOLLIN event.

This test fails because of a kernel bug, which will be fixed by a follow-up
commit.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Link: https://patch.msgid.link/b11947013563875c046c0b0959c29fd95eeebd34.1780422138.git.namcao@linutronix.de
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
---

diff --git a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c b/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c
index 8bc57a2ef966b..f6f1a7ff01b05 100644
--- a/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c
+++ b/tools/testing/selftests/filesystems/epoll/epoll_wakeup_test.c
@@ -3493,4 +3493,49 @@ TEST(epoll64)
 	close(ctx.sfd[1]);
 }
 
+static void *epoll65_wait(void *ctx_)
+{
+	struct epoll_mtcontext *ctx = ctx_;
+	struct epoll_event event;
+
+	for (int i = 0; i < 100000; ++i) {
+		if (!epoll_wait(ctx->efd[0], &event, 1, 0))
+			return (void *)ENODATA;
+	}
+
+	return (void *)0;
+}
+
+TEST(epoll65)
+{
+	struct epoll_mtcontext ctx;
+	struct epoll_event event;
+	int64_t dummy_data = 99;
+	pthread_t threads[64];
+	uintptr_t ret;
+	int i, err;
+
+	ctx.efd[0] = epoll_create(1);
+	ASSERT_GE(ctx.efd[0], 0);
+	ctx.efd[1] = eventfd(0, 0);
+	ASSERT_GE(ctx.efd[1], 0);
+
+	event.events = EPOLLIN;
+	err = epoll_ctl(ctx.efd[0], EPOLL_CTL_ADD, ctx.efd[1], &event);
+	ASSERT_EQ(err, 0);
+
+	write(ctx.efd[1], &dummy_data, sizeof(dummy_data));
+
+	for (i = 0; i < ARRAY_SIZE(threads); ++i)
+		ASSERT_EQ(pthread_create(&threads[i], NULL, epoll65_wait, &ctx), 0);
+
+	for (i = 0; i < ARRAY_SIZE(threads); ++i) {
+		ASSERT_EQ(pthread_join(threads[i], (void **)&ret), 0);
+		ASSERT_EQ(ret, 0);
+	}
+
+	close(ctx.efd[0]);
+	close(ctx.efd[1]);
+}
+
 TEST_HARNESS_MAIN