linux-kernel - Re: [syzbot] possible deadlock in del

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Date:   Tue, 13 Apr 2021 14:43:35 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzkaller <syzkaller@...glegroups.com>,
        syzbot <syzbot+61e04e51b7ac86930589@...kaller.appspotmail.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jens Axboe <axboe@...nel.dk>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, KVM list <kvm@...r.kernel.org>,
        linux-block <linux-block@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>, masahiroy@...nel.org,
        Ingo Molnar <mingo@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        rafael.j.wysocki@...el.com,
        Sean Christopherson <seanjc@...gle.com>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Will Deacon <will@...nel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [syzbot] possible deadlock in del_gendisk

On Tue, 13 Apr 2021 14:40:09 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> ------------[ cut here ]------------
> raw_local_irq_restore() called with IRQs enabled
> WARNING: CPU: 0 PID: 8777 at kernel/locking/irqflag-debug.c:9 warn_bogus_irq_restore kernel/locking/irqflag-debug.c:9 [inline]
> WARNING: CPU: 0 PID: 8777 at kernel/locking/irqflag-debug.c:9 warn_bogus_irq_restore+0x1d/0x20 kernel/locking/irqflag-debug.c:7

In fact, when you have the above, which is a WARN() with text:

 "raw_local_irq_restore() called with IRQs enabled"

It is pretty much guaranteed that all triggers of this bug will have the
above warning with the same text.

-- Steve