linux-kernel - Re: [PATCH v3 07/22] kthread: Detect when a kthread work is used by more workers

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Date:	Mon, 23 Nov 2015 17:27:03 -0500
From:	Tejun Heo <tj@...nel.org>
To:	Petr Mladek <pmladek@...e.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Josh Triplett <josh@...htriplett.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jiri Kosina <jkosina@...e.cz>, Borislav Petkov <bp@...e.de>,
	Michal Hocko <mhocko@...e.cz>, linux-mm@...ck.org,
	Vlastimil Babka <vbabka@...e.cz>, linux-api@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 07/22] kthread: Detect when a kthread work is used by
 more workers

Hello,

On Wed, Nov 18, 2015 at 02:25:12PM +0100, Petr Mladek wrote:
> @@ -610,6 +625,12 @@ repeat:
>  	if (work) {
>  		__set_current_state(TASK_RUNNING);
>  		work->func(work);
> +
> +		spin_lock_irq(&worker->lock);
> +		/* Allow to queue the work into another worker */
> +		if (!kthread_work_pending(work))
> +			work->worker = NULL;
> +		spin_unlock_irq(&worker->lock);

Doesn't this mean that the work item can't be freed from its callback?
That pattern tends to happen regularly.

Thanks.

-- 
tejun
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