linux-kernel - Re: [PATCH 1/2] PM / sleep: ensure deferred probe workqueue is finished in wait_for_device

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Date:	Thu, 08 Oct 2015 22:50:02 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alan Stern <stern@...land.harvard.edu>,
	Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH 1/2] PM / sleep: ensure deferred probe workqueue is finished in wait_for_device_probe

On Thursday, October 08, 2015 11:57:06 AM Grygorii Strashko wrote:
> Now wait_for_device_probe() waits for currently executing probes to finish,
> but it doesn't take into account deferred probing mechanism. As result,
> nothing prevents deferred probe workqueue to continue probing devices right
> after wait_for_device_probe() is finished.
> 
> Hence, lest ensure deferred probe workqueue is finished in

s/lest/let's/

> wait_for_device_probe() before proceeding.
> 
> Cc: Alan Stern <stern@...land.harvard.edu>
> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
> Cc: Thierry Reding <thierry.reding@...il.com>
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> ---
>  drivers/base/dd.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
> index be0eb46..98de1a5 100644
> --- a/drivers/base/dd.c
> +++ b/drivers/base/dd.c
> @@ -391,6 +391,10 @@ int driver_probe_done(void)
>   */
>  void wait_for_device_probe(void)
>  {
> +	/* wait for the deferred probe workqueue to finish */
> +	if (driver_deferred_probe_enable)
> +		flush_workqueue(deferred_wq);
> +
>  	/* wait for the known devices to complete their probing */
>  	wait_event(probe_waitqueue, atomic_read(&probe_count) == 0);
>  	async_synchronize_full();

I'm not sure if this is sufficient.

Something may be added to the workqueue right after you've flushed it and
then be reporobed after the wait_event() in theory.  Or am I missing anything?

Thanks,
Rafael

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