Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751727AbdFGU4F (ORCPT ); Wed, 7 Jun 2017 16:56:05 -0400 Received: from mail-pf0-f176.google.com ([209.85.192.176]:33539 "EHLO mail-pf0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751460AbdFGU4D (ORCPT ); Wed, 7 Jun 2017 16:56:03 -0400 Date: Wed, 7 Jun 2017 13:56:01 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Vlastimil Babka cc: Larry Finger , Andrew Morton , LKML , linux-mm@kvack.org Subject: Re: Sleeping BUG in khugepaged for i586 In-Reply-To: <9ab81c3c-e064-66d2-6e82-fc9bac125f56@suse.cz> Message-ID: References: <968ae9a9-5345-18ca-c7ce-d9beaf9f43b6@lwfinger.net> <20170605144401.5a7e62887b476f0732560fa0@linux-foundation.org> <1e883924-9766-4d2a-936c-7a49b337f9e2@lwfinger.net> <9ab81c3c-e064-66d2-6e82-fc9bac125f56@suse.cz> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 882 Lines: 19 On Wed, 7 Jun 2017, Vlastimil Babka wrote: > >> Hmm I'd expect such spin lock to be reported together with mmap_sem in > >> the debugging "locks held" message? > > > > My bisection of the problem is about half done. My latest good version is commit > > 7b8cd33 and the latest bad one is 2ea659a. Only about 7 steps to go. > > Hmm, your bisection will most likely just find commit 338a16ba15495 > which added the cond_resched() at mm/khugepaged.c:655. CCing David who > added it. > I agree it's probably going to bisect to 338a16ba15495 since it's the cond_resched() at the line number reported, but I think there must be something else going on. I think the list of locks held by khugepaged is correct because it matches with the implementation. The preempt_count(), as suggested by Andrew, does not. If this is reproducible, I'd like to know what preempt_count() is.