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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Tue, 7 Jan 2020 17:01:56 +0100
Message-ID: <CACT4Y+arQyPjzHSFy1MkVF2jNPJbu262_FTL5ma9AnWkXosY1g@mail.gmail.com>
Subject: Re: INFO: task hung in fb_release
To:     syzbot <syzbot+d130c4a0890561cfac5b@syzkaller.appspotmail.com>,
        Rex.Zhu@amd.com, David Airlie <airlied@linux.ie>,
        alexander.deucher@amd.com, amd-gfx@lists.freedesktop.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        christian.koenig@amd.com, david1.zhou@amd.com,
        DRI <dri-devel@lists.freedesktop.org>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Sam Ravnborg <sam@ravnborg.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Cc:     Daniel Vetter <daniel.vetter@ffwll.ch>
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Sender: linux-kernel-owner@vger.kernel.org
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On Tue, Jan 7, 2020 at 4:48 PM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Mon, Dec 23, 2019 at 02:31:01AM -0800, syzbot wrote:
> > syzbot has bisected this bug to:
> >
> > commit e3933f26b657c341055443103bad331f4537b113
> > Author: Rex Zhu <Rex.Zhu@amd.com>
> > Date:   Tue Jan 16 10:35:15 2018 +0000
> >
> >     drm/amd/pp: Add edit/commit/show OD clock/voltage support in sysfs
>
> Pretty sure you don't even have that driver loaded ... from the config:
>
> # CONFIG_DRM_AMDGPU is not set
>
> :-)

Yes, it seems the bug is very flaky and flakiness changes over time.
And this is combined with non-deterministic kernel build bug:
https://github.com/google/syzkaller/issues/1271#issuecomment-559093018
It builds the same kernel, but gets a different result, so it's like
"nope, this commit very much affects the kernel so could be the root
cause"...


> Cheers, Daniel
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12b5a799e00000
> > start commit:   c6017471 Merge tag 'xfs-5.5-fixes-2' of git://git.kernel.o..
> > git tree:       upstream
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=11b5a799e00000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16b5a799e00000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=7f6119e2e3675a73
> > dashboard link: https://syzkaller.appspot.com/bug?extid=d130c4a0890561cfac5b
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=169b1925e00000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12b9623ee00000
> >
> > Reported-by: syzbot+d130c4a0890561cfac5b@syzkaller.appspotmail.com
> > Fixes: e3933f26b657 ("drm/amd/pp: Add edit/commit/show OD clock/voltage
> > support in sysfs")
> >
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
>
> --
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