linux-kernel - Re: [syzbot] INFO: task hung in perf_event_free

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Message-ID: <YH/wggx86Ph1bwPi@hirez.programming.kicks-ass.net>
Date:   Wed, 21 Apr 2021 11:29:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     syzbot <syzbot+7692cea7450c97fa2a0a@...kaller.appspotmail.com>
Cc:     acme@...nel.org, acme@...hat.com,
        alexander.shishkin@...ux.intel.com, andrii@...nel.org,
        ast@...nel.org, bpf@...r.kernel.org, cobranza@...coecuador.com,
        daniel@...earbox.net, eranian@...gle.com, john.fastabend@...il.com,
        jolsa@...hat.com, kafai@...com, kpsingh@...nel.org,
        linux-kernel@...r.kernel.org, mark.rutland@....com,
        mingo@...nel.org, mingo@...hat.com, namhyung@...nel.org,
        netdev@...r.kernel.org, songliubraving@...com,
        syzkaller-bugs@...glegroups.com, tglx@...utronix.de,
        torvalds@...ux-foundation.org, vincent.weaver@...ne.edu, yhs@...com
Subject: Re: [syzbot] INFO: task hung in perf_event_free_task

On Tue, Apr 20, 2021 at 02:10:22AM -0700, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    7af08140 Revert "gcov: clang: fix clang-11+ build"
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15416871d00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=c0a6882014fd3d45
> dashboard link: https://syzkaller.appspot.com/bug?extid=7692cea7450c97fa2a0a
> compiler:       Debian clang version 11.0.1-2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=145c9ffed00000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12de31ded00000

When I build that C file and run it, it completes. AFAICT that's not the
expected outcome given we're looking for a hung-task scenario. Hmm?