linux-kernel - Re: drm/mtrr: possible deadlock

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Date:   Tue, 15 Aug 2017 11:30:20 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Dou Liyang <douly.fnst@...fujitsu.com>
Cc:     daniel.vetter@...el.com, jani.nikula@...ux.intel.com,
        seanpaul@...omium.org, David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: drm/mtrr: possible deadlock

On Tue, Aug 15, 2017 at 11:20 AM, Dou Liyang <douly.fnst@...fujitsu.com> wrote:
> Hi Dmitry,
>
> At 08/15/2017 03:18 PM, Dmitry Vyukov wrote:
>>
>> Hello,
>>
>> I am getting the following deadlock report while booting linux-next on
>> 91dfed74eabcdae9378131546c446442c29bf769 in qemu. Config is attached.
>>
>>
>> WARNING: possible recursive locking detected
>> 4.13.0-rc4-next-20170811 #2 Not tainted
>> --------------------------------------------
>> swapper/0/1 is trying to acquire lock:
>>  (cpu_hotplug_lock.rw_sem){++++}, at: [<ffffffff816a19fc>]
>> stop_machine+0x1c/0x40 kernel/stop_machine.c:596
>>
>> but task is already holding lock:
>>  (cpu_hotplug_lock.rw_sem){++++}, at: [<ffffffff812aad6d>]
>> get_online_cpus include/linux/cpu.h:126 [inline]
>>  (cpu_hotplug_lock.rw_sem){++++}, at: [<ffffffff812aad6d>]
>> mtrr_add_page+0x1bd/0xe80 arch/x86/kernel/cpu/mtrr/main.c:328
>>
>
> I guess you may want this.
>
> https://lkml.org/lkml/2017/8/14/7
>
> and the solution by Thomas
>
> https://lkml.org/lkml/2017/8/14/64


Will try that. Thanks!