linux-kernel - Re: [RFC PATCH] hung_task: Dump blocker task if it is not hung

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Message-Id: <20250730225556.d05b77b108c23ce05e9079e5@kernel.org>
Date: Wed, 30 Jul 2025 22:55:56 +0900
From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
To: Sergey Senozhatsky <senozhatsky@...omium.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>, Waiman Long <longman@...hat.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>, Steven Rostedt <rostedt@...dmis.org>, Tomasz Figa
 <tfiga@...omium.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] hung_task: Dump blocker task if it is not hung

On Wed, 30 Jul 2025 22:28:45 +0900
Sergey Senozhatsky <senozhatsky@...omium.org> wrote:

> On (25/07/30 18:53), Masami Hiramatsu (Google) wrote:
> > From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> > 
> > Dump the lock blocker task if it is not hung because if the blocker
> > task is also hung, it should be dumped by the detector. This will
> > de-duplicate the same stackdumps if the blocker task is also blocked
> > by another task (and hung).
> 
> [..]
> 
> >  #ifdef CONFIG_DETECT_HUNG_TASK_BLOCKER
> > -static void debug_show_blocker(struct task_struct *task)
> > +static void debug_show_blocker(struct task_struct *task, unsigned long timeout)
> >  {
> >  	struct task_struct *g, *t;
> >  	unsigned long owner, blocker, blocker_type;
> > @@ -153,41 +193,21 @@ static void debug_show_blocker(struct task_struct *task)
> >  			       task->comm, task->pid, t->comm, t->pid);
> >  			break;
> >  		}
> > -		sched_show_task(t);
> > +		/* Avoid duplicated task dump, skip if the task is also hung. */
> > +		if (!task_is_hung(t, timeout))
> > +			sched_show_task(t);
> >  		return;
> >  	}
> 
> This patch seems to be against the tree that is significantly
> behind the current linux-next.  Namely it's in conflict with
> linux-next's commit 77da18de55ac6.

Ah, yes. I just used v6.16 for testing. OK, let me update it
against the linux-next.

Thank you,

-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>