Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <00000000000036e81e058507565b@google.com> <alpine.LNX.2.21.1903271021290.994@nippy.intranet>
In-Reply-To: <alpine.LNX.2.21.1903271021290.994@nippy.intranet>
From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Thu, 28 Mar 2019 09:21:33 +0100
Message-ID: <CACT4Y+Ya21HPJVEcsGRgZLK+F+Q5kV-fEp3O755GC9WWB_D=DA@mail.gmail.com>
Subject: Re: INFO: rcu detected stall in __perf_sw_event
To:     Finn Thain <fthain@telegraphics.com.au>
Cc:     syzbot <syzbot+a41ac89a0712acde0e84@syzkaller.appspotmail.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        funaho@jurai.org, Geert Uytterhoeven <geert@linux-m68k.org>,
        jolsa@redhat.com, LKML <linux-kernel@vger.kernel.org>,
        linux-m68k@lists.linux-m68k.org, Ingo Molnar <mingo@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Mar 27, 2019 at 12:28 AM Finn Thain <fthain@telegraphics.com.au> wrote:
>
> On Tue, 26 Mar 2019, syzbot wrote:
>
> > syzbot has bisected this bug to:
> >
> > commit cf85d89562f39cc7ae73de54639f1915a9195b7a
> > Author: Finn Thain <fthain@telegraphics.com.au>
> > Date:   Fri May 25 07:34:36 2018 +0000
> >
> >    m68k/mac: Enable PDMA for PowerBook 500 series
> >
>
> Looks like a false positive. But if you really are running syzkaller on a
> PowerBook 500, you'll want to check that you have an FPU, otherwise a CPU
> erratum will probably mess up your results.

Agree. I've included it into the big bisection analysis as "hard to
reproduce" case:
https://lkml.org/lkml/2019/3/27/788


> --
>
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1226cb8b200000
> > start commit:   b0314565 Merge tag 'for_linus' of git://git.kernel.org/pub..
> > git tree:       upstream
> > final crash:    https://syzkaller.appspot.com/x/report.txt?x=1126cb8b200000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=1626cb8b200000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=8f00801d7b7c4fe6
> > dashboard link: https://syzkaller.appspot.com/bug?extid=a41ac89a0712acde0e84
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1707cd2f400000
> >
> > Reported-by: syzbot+a41ac89a0712acde0e84@syzkaller.appspotmail.com
> > Fixes: cf85d89562f3 ("m68k/mac: Enable PDMA for PowerBook 500 series")
> >
> > For information about bisection process see: https://goo.gl/tpsmEJ#bisection
>
> --
> You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/alpine.LNX.2.21.1903271021290.994%40nippy.intranet.
> For more options, visit https://groups.google.com/d/optout.