linux-kernel - Re: INFO: rcu detected stall in new_sync

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Message-ID: <e455c0b6-2d3e-37c3-bb40-dcd96d1ed124@I-love.SAKURA.ne.jp>
Date:   Tue, 7 Jan 2020 06:08:23 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot <syzbot+8a95855c8a4649d98244@...kaller.appspotmail.com>,
        akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, syzkaller-bugs@...glegroups.com
Subject: Re: INFO: rcu detected stall in new_sync_read

On 2020/01/07 5:54, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    bed72351 Merge tag 'kbuild-fixes-v5.5-2' of git://git.kern..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1747aec6e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=874bac2ff63646fa
> dashboard link: https://syzkaller.appspot.com/bug?extid=8a95855c8a4649d98244
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11c26859e00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1307e6b9e00000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+8a95855c8a4649d98244@...kaller.appspotmail.com
> 

Dmitry, this looks like yet another stall report doing sched_setattr(SCHED_RR)
followed by sendfile()/fallocate() etc...