linux-kernel - Re: Bug: task hung in shmem_swapin

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Message-Id: <431D467D-10F3-4316-A34B-6C1315178B05@m.fudan.edu.cn>
Date: Sun, 12 Jan 2025 20:51:20 +0800
From: Kun Hu <huk23@...udan.edu.cn>
To: Matthew Wilcox <willy@...radead.org>
Cc: hch@....de,
 jlayton@...nel.org,
 kirill.shutemov@...ux.intel.com,
 vbabka@...e.cz,
 william.kucharski@...cle.com,
 rppt@...ux.ibm.com,
 dhowells@...hat.com,
 akpm@...ux-foundation.org,
 hughd@...gle.com,
 linux-fsdevel@...r.kernel.org,
 linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: Bug: task hung in shmem_swapin_folio

> 2025年1月12日 20:02，Matthew Wilcox <willy@...radead.org> 写道：
> 
> On Sun, Jan 12, 2025 at 05:46:24PM +0800, Kun Hu wrote:
>> Hello,
>> 
>> When using our customized fuzzer tool to fuzz the latest Linux kernel, the following crash (42s)
>> was triggered.
> 
> It's not a crash.  It's a warning.  You've just configured your kernel
> to crash when emitting a warning.
> 
> What you need to do is poke around in the reproducer you've found and
> figure out what it is you're doing that causes this warning.  Are
> you constraining your task with memory groups, for example?  Are you
> doing a huge amount of I/O which is causing your disk to be
> bottlenecked?  Something else?
> 
> It's all very well to automate finding bugs, but you're asking other
> people to do a lot of the work for you.
> 

Thank you very much and sorry at the same time.

We know that most of the work of locating a issue should be done by the reporter, but having just looked into fuzzing against the kernel, the background knowledge of the kernel is not very familiar at the moment. That's why we've taken the approach of sending out a report first, and after getting professional feedback from the maintainers, we're able to target test a particular subsystem or module for them to improve efficiency.

Our strategy seems to be incorrect and certainly due to our lack of Kernel expertise, again I apologize, we will improve and hopefully report really useful information.

————
Thanks,
Kun Hu