Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752768AbZLVHue (ORCPT ); Tue, 22 Dec 2009 02:50:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751867AbZLVHud (ORCPT ); Tue, 22 Dec 2009 02:50:33 -0500 Received: from qw-out-2122.google.com ([74.125.92.26]:44626 "EHLO qw-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750972AbZLVHuc convert rfc822-to-8bit (ORCPT ); Tue, 22 Dec 2009 02:50:32 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=wblMcItK+mMzKvBsLjVZgfT6frWxso6l1VVTaq6YGibMPsV8NiHQoI4ixpF387G/vV 4PMJWdN/o8sokmZJzm0kjViE9IMPIUgjpdqGoZg0bBcKvMeHt1BNuz21r6ZZ94OCeT3j JicLV8XeMN30ubczMimac9ViI7oudRjV+dP90= MIME-Version: 1.0 In-Reply-To: <7b6bb4a50912212341q1e35689cuc40394ae31f96bd0@mail.gmail.com> References: <1261441037.3273.254.camel@localhost> <7b6bb4a50912212142i6892320q7a84cf185a4a2621@mail.gmail.com> <2375c9f90912212319v63dc692bg13b918fe6ea03299@mail.gmail.com> <7b6bb4a50912212341q1e35689cuc40394ae31f96bd0@mail.gmail.com> Date: Tue, 22 Dec 2009 15:50:31 +0800 Message-ID: <2375c9f90912212350s7e48a4bfp2c5b3863f5969097@mail.gmail.com> Subject: Re: 2.6.33-rc1 unusable due to scheduler issues, circular locking, WARNs and BUGs From: =?UTF-8?Q?Am=C3=A9rico_Wang?= To: Xiaotian Feng Cc: Eric Paris , linux-kernel@vger.kernel.org, mingo@elte.hu, peterz@infradead.org, efault@gmx.de Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2166 Lines: 52 On Tue, Dec 22, 2009 at 3:41 PM, Xiaotian Feng wrote: > On Tue, Dec 22, 2009 at 3:19 PM, Américo Wang wrote: >> [Fix top-posting] >> >> On Tue, Dec 22, 2009 at 1:42 PM, Xiaotian Feng wrote: >>> >>> On Tue, Dec 22, 2009 at 8:17 AM, Eric Paris wrote: >>>> Trying to build a kernel on a 48 core x86_64 box using make -j 64 and >>>> I'm exploding in the scheduler.  I'm running (and building) kernel >>>> f7b84a6ba7eaeba4e1df8feddca1473a7db369a5  There are three distinct >>>> signatures of problems.  Some boots I'll see all 3 of these failures >>>> sometimes only 1 or 2 of them.  That's the reason they are kinda split >>>> up in dmesg. >>>> >>>> 1) gcc/3141 is trying to acquire lock: >>>>  (&(&sem->wait_lock)->rlock){......}, at: [] __down_read_trylock+0x13/0x46 >>>> >>>> but task is already holding lock: >>>>  (&rq->lock){-.-.-.}, at: [] task_rq_lock+0x51/0x83 >>>> >>>> 2) WARN() in kernel/sched_fair.c:1001 hrtick_start_fair() >>>> >>>> 3) NULL pointer dereference at 0000000000000168 in check_preempt_wakeup >>>>      kernel/sched_fair.c >>>> >>>> Full backtraces are in the attached dmesg. >>>> >>> Does a revert of cd29fe6f2637cc2ccbda5ac65f5332d6bf5fa3c6 fix this problem? >> >> >> I don't think so... >> >> I think the most suspicious commit here is ab19cb23. It kicked >> "local_irq_save()" >> out, which means if the task is selected to run on another cpu which doesn't >> disable irq, we will have a page fault, thun we will try to hold mm->mmap_sem >> while we are holding rq->lock already. > > The page fault is from kernel  NULL pointer deref.  You should connect > the lockdep warning and kernel BUG together. > Interesting. 1) Doesn't this NULL ptr def expose that we have a potential problem? 2) For NULL ptr def problem, commit 3a7e73a2e2 seems more suspicious.. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/