linux-kernel - Re: [PATCH 0/2] hung_task: Dump the blocking task stacktrace

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Message-ID: <8ca57548-4b18-401d-bfda-95bc12216adf@redhat.com>
Date: Wed, 19 Feb 2025 15:20:39 -0500
From: Waiman Long <llong@...hat.com>
To: Lance Yang <ioworker0@...il.com>, mhiramat@...nel.org
Cc: 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>,
 Kent Overstreet <kent.overstreet@...ux.dev>,
 Yongliang Gao <leonylgao@...cent.com>, Steven Rostedt <rostedt@...dmis.org>,
 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 0/2] hung_task: Dump the blocking task stacktrace


On 2/19/25 10:02 AM, Lance Yang wrote:
> On Wed, Feb 19, 2025 at 9:33 PM Lance Yang <ioworker0@...il.com> wrote:
>> CC linux-mm
>>
>> On Wed, Feb 19, 2025 at 9:00 PM Masami Hiramatsu (Google)
>> <mhiramat@...nel.org> wrote:
>>> Hi,
>>>
>>> The hung_task detector is very useful for detecting the lockup.
>>> However, since it only dumps the blocked (uninterruptible sleep)
>>> processes, it is not enough to identify the root cause of that
>>> lockup.
>>>
>>> For example, if a process holds a mutex and sleep an event in
>>> interruptible state long time, the other processes will wait on
>>> the mutex in uninterruptible state. In this case, the waiter
>>> processes are dumped, but the blocker process is not shown
>>> because it is sleep in interruptible state.
> Cool! I just ran into something similar today, but with rwsem. In that
> case, the blocked process was locked up, and we could not identify
> the root cause either ;(

Once this patch series is settled down, we can extend rwsem to provide 
similar feature.

Cheers,
Longman