From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752294Ab2GAHCv (ORCPT ); Sun, 1 Jul 2012 03:02:51 -0400 Received: from ud10.udmedia.de ([194.117.254.50]:40332 "EHLO mail.ud10.udmedia.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751784Ab2GAHCb (ORCPT ); Sun, 1 Jul 2012 03:02:31 -0400 Date: Sun, 1 Jul 2012 09:02:28 +0200 From: Markus Trippelsdorf To: Jan Engelhardt Cc: Linux Kernel Mailing List , simon@fire.lp0.eu Subject: Re: Leap second insertion causes futex to repeatedly timeout Message-ID: <20120701070228.GA246@x4> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2012.07.01 at 02:57 +0200, Jan Engelhardt wrote: > > This year's leap second insertion has had the strange effect on at least > Linux versions 3.4.4 (my end) and 3.5-rc4 (Simon's box, Cc) that certain > processes use up all CPU power, because of futexes repeatedly timing > out. This seems to only affect certain processes. > > Simon observes - http://s85.org/owXfmLvt - that > Firefox/Thunderbird/Chrome/Java are affected. On my ntp synchronized Linux 3.5 testbox I saw a similar issue. The leap second was successfully inserted last night: Jul 1 01:59:59 x4 kernel: Clock: inserting leap second 23:59:60 UTC Because glibc-2.16 was released yesterday I've build it this morning. During "make check" I saw several mutex related tests failures. For example /nptl/tst-mutex5a.c failed with a "premature timeout difference" of one second. tst-mutex5a.c: #define TYPE PTHREAD_MUTEX_ADAPTIVE_NP #include "tst-mutex5.c" from tst-mutex5.c: // ... gettimeofday (&tv, NULL); TIMEVAL_TO_TIMESPEC (&tv, &ts); ts.tv_sec += 2; /* Wait 2 seconds. */ err = pthread_mutex_timedlock (&m, &ts); // ... { int clk_tck = sysconf (_SC_CLK_TCK); gettimeofday (&tv2, NULL); tv2.tv_sec -= tv.tv_sec; tv2.tv_usec -= tv.tv_usec; if (tv2.tv_usec < 0) { tv2.tv_usec += 1000000; tv2.tv_sec -= 1; } /* Be a bit tolerant, add one CLK_TCK. */ tv2.tv_usec += 1000000 / clk_tck; if (tv2.tv_usec >= 1000000) { tv2.tv_usec -= 1000000; ++tv2.tv_sec; } if (tv2.tv_sec < 2) { printf ("premature timeout: %ld.%06ld difference\n", tv2.tv_sec, tv2.tv_usec); return 1; } } // ... -- Markus