From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f170.google.com (mail-pd0-f170.google.com [209.85.192.170]) by kanga.kvack.org (Postfix) with ESMTP id 897116B0035 for ; Thu, 10 Jul 2014 14:54:38 -0400 (EDT) Received: by mail-pd0-f170.google.com with SMTP id z10so6368pdj.1 for ; Thu, 10 Jul 2014 11:54:38 -0700 (PDT) Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id ek5si8945382pdb.301.2014.07.10.11.54.36 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 10 Jul 2014 11:54:37 -0700 (PDT) Received: by mail-pa0-f47.google.com with SMTP id kq14so4375pab.6 for ; Thu, 10 Jul 2014 11:54:36 -0700 (PDT) Date: Thu, 10 Jul 2014 11:52:57 -0700 (PDT) From: Hugh Dickins Subject: Re: + shmem-fix-faulting-into-a-hole-while-its-punched-take-2.patch added to -mm tree In-Reply-To: <53BED7F6.4090502@oracle.com> Message-ID: References: <53b45c9b.2rlA0uGYBLzlXEeS%akpm@linux-foundation.org> <53BCBF1F.1000506@oracle.com> <53BD1053.5020401@suse.cz> <53BD39FC.7040205@oracle.com> <53BD67DC.9040700@oracle.com> <53BE8B1B.3000808@oracle.com> <53BECBA4.3010508@oracle.com> <53BED7F6.4090502@oracle.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin Cc: Hugh Dickins , Heiko Carstens , Vlastimil Babka , akpm@linux-foundation.org, davej@redhat.com, koct9i@gmail.com, lczerner@redhat.com, stable@vger.kernel.org, "linux-mm@kvack.org" , LKML On Thu, 10 Jul 2014, Sasha Levin wrote: > On 07/10/2014 01:55 PM, Hugh Dickins wrote: > >> And finally, (not) holding the i_mmap_mutex: > > I don't understand what prompts you to show this particular task. > > I imagine the dump shows lots of other tasks which are waiting to get an > > i_mmap_mutex, and quite a lot of other tasks which are neither waiting > > for nor holding an i_mmap_mutex. > > > > Why are you showing this one in particular? Because it looks like the > > one you fingered yesterday? But I didn't see a good reason to finger > > that one either. > > There are a few more tasks like this one, my criteria was tasks that lockdep > claims were holding i_mmap_mutex, but are actually not. You and Vlastimil enlightened me yesterday that lockdep shows tasks as holding i_mmap_mutex when they are actually waiting to get i_mmap_mutex. Hundreds of those in yesterday's log, hundreds of them in today's. The full log you've sent (thanks) is for a different run from the one you showed in today's mail. No problem with that, except when I assert that trinity-c190 in today's mail is just like trinity-c402 in yesterday's, a task caught at one stage of exit_mmap in the stack dumps, then a later stage of exit_mmap in the locks held dumps, I'm guessing rather than confirming from the log. There's nothing(?) interesting about those tasks, they're just tasks we have been lucky to catch a moment before they reach the i_mmap_mutex hang affecting the majority. > > One new thing that I did notice is that since trinity spins a lot of new children > to test out things like execve() which would kill said children, there tends to > be a rather large amount of new tasks created and killed constantly. > > So if you look at the bottom of the new log (attached), you'll see that there > are quite a few "trinity-subchild" processes trying to die, unsuccessfully. Lots of those in yesterday's log too: waiting to get i_mmap_mutex. I'll pore over the new log. It does help to know that its base kernel is more stable: thanks so much. But whether I can work out any more... Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org