linux-kernel - Re: [syzbot] [wireless?] INFO: task hung in cfg80211_event

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Message-ID: <01ef8d01-dbcb-4f11-844e-77dc26aba640@candelatech.com>
Date: Mon, 14 Oct 2024 07:38:16 -0700
From: Ben Greear <greearb@...delatech.com>
To: Aleksandr Nogikh <nogikh@...gle.com>
Cc: syzbot <syzbot+5506b2556159a1ab6923@...kaller.appspotmail.com>,
 davem@...emloft.net, edumazet@...gle.com, johannes@...solutions.net,
 kuba@...nel.org, linux-kernel@...r.kernel.org,
 linux-wireless@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com,
 syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [wireless?] INFO: task hung in cfg80211_event_work (4)

On 10/14/24 02:54, Aleksandr Nogikh wrote:
> Hi Ben,
> 
> On Fri, Oct 11, 2024 at 11:50 AM Ben Greear <greearb@...delatech.com> wrote:
>>
>> On 10/10/24 08:19, syzbot wrote:
>>> Hello,
>>>
>>> syzbot found the following issue on:
>>>
>>> HEAD commit:    2a130b7e1fcd Merge tag 'kbuild-fixes-v6.12' of git://git.k..
>>> git tree:       upstream
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=1206e79f980000
>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=f38c36a955431c1
>>> dashboard link: https://syzkaller.appspot.com/bug?extid=5506b2556159a1ab6923
>>> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=155b8327980000
>>
>> This looks like something I saw in 6.11 and 6.10.  My guess was that one of the
>> running processes that lockdep does not print locks for is holding the wiphy mtx.
>>
>> Maybe it would help if syzbot would use sysrq to dump all running tasks to the console, and maybe
>> lockdep could print locks for running processes, even if they are marked as potentially
>> unreliable?
> 
> Thanks for the suggestions!
> 
> We do have an open issue re. SysRq:
> https://github.com/google/syzkaller/issues/4200
> I've noted a +1 to that.
> 
> Regarding the locks -- they are actually already printed in the
> original bug report, under "Showing all locks held in the system:". Or
> did you mean something else?

Notice that some processes say they have locks but do not print them.  Lockep
skips printing locks for running processes that are not the current process.

I have added some local code to try printing them anyway, will see if it helps
any...

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com