Commit 282144e0 authored by Roman Penyaev's avatar Roman Penyaev Committed by Linus Torvalds
Browse files

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.

Signed-off-by: default avatarRoman Penyaev <rpenyaev@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Cc: Max Neunhoeffer <max@arangodb.com>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Christopher Kohlhoff <chris.kohlhoff@clearpool.io>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Jes Sorensen <jes.sorensen@gmail.com>
Link: http://lkml.kernel.org/r/20200214170211.561524-2-rpenyaev@suse.de


Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 16b7f3c8

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

+66 −1
Original line number Diff line number Diff line
@@ -7,13 +7,14 @@ 
#include <pthread.h>

#include <sys/epoll.h>

#include <sys/socket.h>

#include <sys/eventfd.h>

#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

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