linux-kernel - Re: [PATCH 5/5] input: twl6040-vibra: remove mutex

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Date:	Tue, 19 Apr 2016 10:08:00 +0200
From:	"H. Nikolaus Schaller" <hns@...delico.com>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Fabio Estevam <fabio.estevam@...escale.com>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	kernel@...a-handheld.com, letux-kernel@...nphoenux.org
Subject: Re: [PATCH 5/5] input: twl6040-vibra: remove mutex


> Am 19.04.2016 um 10:01 schrieb Dmitry Torokhov <dmitry.torokhov@...il.com>:
> 
> On Tue, Apr 19, 2016 at 09:49:01AM +0200, H. Nikolaus Schaller wrote:
>> 
>>> Am 18.04.2016 um 23:20 schrieb Dmitry Torokhov <dmitry.torokhov@...il.com>:
>>> 
>>> On Mon, Apr 18, 2016 at 09:55:41PM +0200, H. Nikolaus Schaller wrote:
>>>> The mutex does not seem to be needed.
>>> 
>>> twl6040_vibra_suspend() and vibra_play_work() may run concurrently, no?
>> 
>> Hm. I don't know about the rule that would give an answer to this question...
> 
> Sorry, that was actually a statement, not really a question.

Indeed. In doubt about the answer we should take measures for the worst case.

> It is
> possible (although very unlikely) that userspace posts play request and
> workqueue will not run until after suspend callback.
> 
> Thinking about it some more I wonder if we better do what
> twl6040_vibra_close() does and cancel the work before shutting off the
> device, so that there is no chance of work executing after suspend
> callback and reenabling the device. This way we can indeed remove the
> mutex.

Ok, I am fine with this.

Will post an update ASAP.

BR and thanks,
Nikolaus