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: <524bd2b9-5322-4012-b1d0-b76edb84ec4f@redhat.com>
Date: Wed, 19 Feb 2025 22:49:09 -0500
From: Waiman Long <llong@...hat.com>
To: Sergey Senozhatsky <senozhatsky@...omium.org>,
 Masami Hiramatsu <mhiramat@...nel.org>
Cc: Steven Rostedt <rostedt@...dmis.org>, 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>,
 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 9:45 PM, Sergey Senozhatsky wrote:
> On (25/02/20 08:09), Masami Hiramatsu wrote:
>> So something like this?
>>
>> unsigned int	block_flags;
>> union {
>> 	struct mutex	*mutex;
>> 	struct rwsem	+rwsem;
>> 	struct rtmutex	*rtmutex;
>> } blocked_on;
>>
>> enum {
>> 	BLOCKED_ON_MUTEX;
>> 	BLOCKED_ON_RWSEM;
>> 	BLOCKED_ON_RTMUTEX;
>> 	BLOCKED_ON_IO;
>> } block_reason;
> I totally like this and always wanted to have something simlar,
> something for all "sleepable" synchronization primitives, lightweight
> enough (memory and CPU usage wise) to run on consumer devices.  I was
> thinking of a rhashtable where each entry represents "sleepable"
> primitive with a "owner" pointer and a list of "blocked on" tasks.
> But I'm sure you'll have a better idea.
>
> If I may add a couple of "wishes", can we also add:
> - completions (so that things like wait_for_completion and
>    synchronize srcu get covered)
> - wait on bit (so that things like lock_buffer and so on get covered)

Bit lock doesn't have a owner field to track the owning task.

Cheers,
Longman

>