linux-kernel - Re: [PATCH v9 08/12] kthread: Detect when a kthread work is used by more workers

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Date:	Mon, 20 Jun 2016 16:10:02 -0400
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 v9 08/12] kthread: Detect when a kthread work is used by
 more workers

Hello,

On Thu, Jun 16, 2016 at 01:17:27PM +0200, Petr Mladek wrote:
> diff --git a/kernel/kthread.c b/kernel/kthread.c
> index 567ec49b4872..8e9548649c86 100644
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -574,6 +574,9 @@ EXPORT_SYMBOL_GPL(__kthread_init_worker);
>   * The works are not allowed to keep any locks, disable preemption or interrupts
>   * when they finish. There is defined a safe point for freezing when one work
>   * finishes and before a new one is started.
> + *
> + * Also the works must not be handled by more workers at the same time, see also
                                                ^
						than one
> + * kthread_queue_work().
>   */
>  int kthread_worker_fn(void *worker_ptr)
>  {
> @@ -710,12 +713,21 @@ kthread_create_worker_on_cpu(int cpu, const char namefmt[], ...)
>  }
>  EXPORT_SYMBOL(kthread_create_worker_on_cpu);
>  
> +static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
> +					     struct kthread_work *work)
> +{
> +	lockdep_assert_held(&worker->lock);
> +	WARN_ON_ONCE(!list_empty(&work->node));
> +	/* Do not use a work with more workers, see kthread_queue_work() */
                                  ^
				  ditto, maybe just say ">1 workers"?

Looks good otherwise.

Thanks.

-- 
tejun