From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758206Ab2C1LGy (ORCPT ); Wed, 28 Mar 2012 07:06:54 -0400 Received: from shelob.oktetlabs.ru ([195.131.132.186]:34746 "EHLO shelob.oktetlabs.ru" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752206Ab2C1LGx (ORCPT ); Wed, 28 Mar 2012 07:06:53 -0400 X-Greylist: delayed 516 seconds by postgrey-1.27 at vger.kernel.org; Wed, 28 Mar 2012 07:06:53 EDT X-DKIM: Sendmail DKIM Filter v2.8.2 shelob.oktetlabs.ru 2B3727F4D9 Authentication-Results: shelob.oktetlabs.ru/2B3727F4D9; dkim=none (no signature) header.i=unknown; dkim-adsp=none Date: Wed, 28 Mar 2012 14:57:59 +0400 From: "Alexandra N. Kossovsky" To: Jason Baron Cc: "Yurij M. Plotnikov" , linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: Dead circle in epoll file descriptor causes soft lockup on kernel 3.2.12 Message-ID: <20120328105757.GS29100@oktetlabs.ru> References: <4F717174.9090008@oktetlabs.ru> <20120327140510.GA2419@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120327140510.GA2419@redhat.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 27, 2012 at 10:05:10AM -0400, Jason Baron wrote: > On Tue, Mar 27, 2012 at 11:51:16AM +0400, Yurij M. Plotnikov wrote: > > Adding epoll file descriptors in each other in circle causes soft > > lockup on kernel 3.2.12 (I'm using Debian kernel > > 3.2.0-0.bpo.1-amd64). The following steps describe the problem: > > > > 1. epoll_create(1) -> 3 > > 2. epoll_create(1) -> 4 > > 3. socket(SOCK_STREAM) -> 5 > > 4. bind(5, 0.0.0.0:0) -> 0 > > 5. listen(5, 1) -> 0 > > 6. epoll_ctl(3, ADD, 5, events = 0) -> 0 > > 7. epoll_ctl(3, ADD, 4, events = EPOLLIN) -> 0 > > 8. epoll_ctl(4, ADD, 3, events = EPOLLIN) -> -1(ELOOP) > > 9. close(3) -> 0 > > 10. close(4) -> 0 > > 11. close(5) -> 0 > > > > After repetaing this sequence 2-3 times soft lockup appers. In > > attachment c program to reproduce this problem. > > > > Good catch. The patch below should fix this - please verify. Thanks. Verified. You patch solves our problem. Thank you very much for fast response. -- Alexandra N. Kossovsky OKTET Labs (http://www.oktetlabs.ru/)