linux-kernel - Re: [PATCH v4 10/22] kthread: Allow to modify delayed kthread work

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Date:	Mon, 25 Jan 2016 14:19:09 -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 v4 10/22] kthread: Allow to modify delayed kthread work

On Mon, Jan 25, 2016 at 04:44:59PM +0100, Petr Mladek wrote:
> +bool mod_delayed_kthread_work(struct kthread_worker *worker,
> +			      struct delayed_kthread_work *dwork,
> +			      unsigned long delay)
> +{
> +	struct kthread_work *work = &dwork->work;
> +	unsigned long flags;
> +	int ret = 0;
> +
> +try_again:
> +	spin_lock_irqsave(&worker->lock, flags);
> +	WARN_ON_ONCE(work->worker && work->worker != worker);
> +
> +	if (work->canceling)
> +		goto out;
> +
> +	ret = try_to_cancel_kthread_work(work, &worker->lock, &flags);
> +	if (ret == -EAGAIN)
> +		goto try_again;
> +
> +	if (work->canceling)

Does this test need to be repeated?  How would ->canceling change
while worker->lock is held?

Thanks.

-- 
tejun