linux-kernel - Re: [alsa-devel] BUG: soft lockup

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Date:   Mon, 6 Nov 2017 11:42:26 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     "Kirill A. Shutemov" <kirill@...temov.name>,
        syzbot 
        <bot+63583aefef5457348dcfa06b87d4fd1378b26b09@...kaller.appspotmail.com>,
        aaron.lu@...el.com, alsa-devel@...a-project.org,
        Michal Hocko <mhocko@...e.com>, Jan Kara <jack@...e.cz>,
        Minchan Kim <minchan@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>, ying.huang@...el.com,
        syzkaller-bugs@...glegroups.com,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>, shli@...com,
        David Rientjes <rientjes@...gle.com>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Andrew Morton <akpm@...ux-foundation.org>,
        zi.yan@...rutgers.edu, Matthew Wilcox <willy@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [alsa-devel] BUG: soft lockup

On Mon, Nov 6, 2017 at 11:39 AM, Takashi Iwai <tiwai@...e.de> wrote:
> On Thu, 02 Nov 2017 10:09:51 +0100,
> Kirill A. Shutemov wrote:
>>
>> On Thu, Nov 02, 2017 at 09:23:58AM +0100, Takashi Iwai wrote:
>> >
>> > Currently the least ALSA timer interrupt period is limited to 1ms.
>> > Does it still too much?
>> >
>> > Can the reproducer triggers it reliably?  If yes, could you forward
>> > it, too (and config as well), so that I'll try to dig down more exact
>> > code paths?
>>
>> All of that is part of original report:
>>
>> http://lkml.kernel.org/r/94eb2c19df188b1926055cf13c21@google.com
>>
>> marc.info hasn't stored repro.c for some reasone. Attached.
>>
>> I've just check it reproduces reliably for me in KVM.
>>
>> I also checked that it's not specific to THP -- still trigirable with huge
>> pages disabled.
>
> I guess this is the same issue Jerome forwarded recently, and it was
> fixed by limiting the amount of ALSA timer instances.  I queued the
> fix in sound git tree for-linus branch, commit
> 9b7d869ee5a77ed4a462372bb89af622e705bfb8
>     ALSA: timer: Limit max instances per timer
>
> It'll be likely included in 4.14 final.

Thanks

Let's also tell the bot what fixes this:

#syz fix: ALSA: timer: Limit max instances per timer