From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f197.google.com (mail-pf0-f197.google.com [209.85.192.197]) by kanga.kvack.org (Postfix) with ESMTP id 372816B026D for ; Tue, 5 Dec 2017 04:19:30 -0500 (EST) Received: by mail-pf0-f197.google.com with SMTP id m9so15844850pff.0 for ; Tue, 05 Dec 2017 01:19:30 -0800 (PST) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id j25sor3606067pgn.17.2017.12.05.01.19.28 for (Google Transport Security); Tue, 05 Dec 2017 01:19:28 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <80ba65b6-d0c2-2d3a-779b-a134af8a9054@lge.com> References: <94eb2c0d010a4e7897055f70535b@google.com> <20171204083339.GF8365@quack2.suse.cz> <80ba65b6-d0c2-2d3a-779b-a134af8a9054@lge.com> From: Dmitry Vyukov Date: Tue, 5 Dec 2017 10:19:07 +0100 Message-ID: Subject: Re: possible deadlock in generic_file_write_iter (2) Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Byungchul Park Cc: Jan Kara , syzbot , Andrew Morton , Johannes Weiner , jlayton@redhat.com, LKML , Linux-MM , Mel Gorman , npiggin@gmail.com, rgoldwyn@suse.com, syzkaller-bugs@googlegroups.com, Peter Zijlstra , kernel-team@lge.com On Tue, Dec 5, 2017 at 5:58 AM, Byungchul Park wrote: > On 12/4/2017 5:33 PM, Jan Kara wrote: >> >> Hello, >> >> adding Peter and Byungchul to CC since the lockdep report just looks >> strange and cross-release seems to be involved. Guys, how did #5 get into >> the lock chain and what does put_ucounts() have to do with sb_writers >> there? Thanks! > > > Hello Jan, > > In order to get full stack of #5, we have to pass a boot param, > "crossrelease_fullstack", to the kernel. Now that it only informs > put_ucounts() in the call trace, it's hard to find out what exactly > happened at that time, but I can tell #5 shows: > > When acquire(sb_writers) in put_ucounts(), it was on the way to > complete((completion)&req.done) of wait_for_completion() in > devtmpfs_create_node(). > > If acquire(sb_writers) in put_ucounts() is stuck, then > wait_for_completion() in devtmpfs_create_node() would be also > stuck, since complete() being in the context of acquire(sb_writers) > cannot be called. > > This is why cross-release added the lock chain. Hi, What is cross-release? Is it something new? Should we always enable crossrelease_fullstack during testing? Thanks -- 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