linux-kernel - Re: [PATCH 1/2] hung_task: Show the blocker task if the task is hung on mutex

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Message-ID: <0948872d-06cf-45da-81d0-397197fdbc67@redhat.com>
Date: Wed, 19 Feb 2025 21:21:31 -0500
From: Waiman Long <llong@...hat.com>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
 Steven Rostedt <rostedt@...dmis.org>
Cc: Waiman Long <llong@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
 Andrew Morton <akpm@...ux-foundation.org>, Boqun Feng
 <boqun.feng@...il.com>, Joel Granados <joel.granados@...nel.org>,
 Anna Schumaker <anna.schumaker@...cle.com>, Lance Yang
 <ioworker0@...il.com>, Kent Overstreet <kent.overstreet@...ux.dev>,
 Yongliang Gao <leonylgao@...cent.com>, Tomasz Figa <tfiga@...omium.org>,
 Sergey Senozhatsky <senozhatsky@...omium.org>, linux-kernel@...r.kernel.org,
 Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH 1/2] hung_task: Show the blocker task if the task is hung
 on mutex

On 2/19/25 9:07 PM, Masami Hiramatsu (Google) wrote:
> On Wed, 19 Feb 2025 18:55:31 -0500
> Steven Rostedt <rostedt@...dmis.org> wrote:
>
>> On Thu, 20 Feb 2025 07:56:39 +0900
>> Masami Hiramatsu (Google) <mhiramat@...nel.org> wrote:
>>
>>>>>> this field, we don't need to take lock, though taking the wait_lock may
>>>>>> still be needed to examine other information inside the mutex.
>>> Do we need to take it just for accessing owner, which is in an atomic?
>> Updating the task_struct would be in the same location as the blocked_on is
>> anyway. I would make it into a wrapper function that is a nop when disabled.
> Should we make it depends on DEBUG_MUTEXES too? I think no. We can introduce
> a different kconfig and wrapper function which calls debug_mutex_*().

No, I don't think so. In fact, the mutex debug code can make use of the 
new fields for additional checking. I believe DEBUG_MUTEXES should 
select the new option.

Cheers,
Longman