linux-kernel - Re: [PATCH] input: pcap2: avoid calling mutex

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Message-Id: <20140406233744.c40387e9bead51ee48e5ebd1@ao2.it>
Date:	Sun, 6 Apr 2014 23:37:44 +0200
From:	Antonio Ospite <ao2@....it>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Alexey Khoroshilov <khoroshilov@...ras.ru>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
	ldv-project@...uxtesting.org, Daniel Ribeiro <drwyrm@...il.com>,
	Ilya Petrov <ilya.muromec@...il.com>,
	Antonio Ospite <ospite@...denti.unina.it>
Subject: Re: [PATCH] input: pcap2: avoid calling mutex_lock() in irq handler

On Sun, 6 Apr 2014 13:24:36 -0700
Dmitry Torokhov <dmitry.torokhov@...il.com> wrote:

> On Sun, Apr 06, 2014 at 12:54:50AM +0400, Alexey Khoroshilov wrote:
> > pcap_keys_handler() calls ezx_pcap_read() that calls mutex_lock().
> > pcap_keys_handler() is registered as nonthreaded irq handler,
> > that means sleeping function is called in irq handler.
> > 
> > The patch makes a switch to threaded irq handling.
> > Compile tested only.
> > 
> > Found by Linux Driver Verification project (linuxtesting.org).
> > 
> > Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>
> > ---
> >  drivers/input/misc/pcap_keys.c | 10 ++++++----
> >  1 file changed, 6 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/input/misc/pcap_keys.c b/drivers/input/misc/pcap_keys.c
> > index cd230365166e..2a10f3a30969 100644
> > --- a/drivers/input/misc/pcap_keys.c
> > +++ b/drivers/input/misc/pcap_keys.c
> > @@ -79,13 +79,15 @@ static int pcap_keys_probe(struct platform_device *pdev)
> >  	if (err)
> >  		goto fail_allocate;
> >  
> > -	err = request_irq(pcap_to_irq(pcap_keys->pcap, PCAP_IRQ_ONOFF),
> > -			pcap_keys_handler, 0, "Power key", pcap_keys);
> > +	err = request_threaded_irq(pcap_to_irq(pcap_keys->pcap, PCAP_IRQ_ONOFF),
> > +				   NULL, pcap_keys_handler, 0,
> > +				   "Power key", pcap_keys);
> >  	if (err)
> >  		goto fail_register;
> >  
> > -	err = request_irq(pcap_to_irq(pcap_keys->pcap, PCAP_IRQ_MIC),
> > -			pcap_keys_handler, 0, "Headphone button", pcap_keys);
> > +	err = request_threaded_irq(pcap_to_irq(pcap_keys->pcap, PCAP_IRQ_MIC),
> > +				   NULL, pcap_keys_handler, 0,
> > +				   "Headphone button", pcap_keys);
> 
> So I guess we do need threaded IRQ here, but I do not see the pcap's
> irqchip specifying IRQCHIP_ONESHOT_SAFE so I do not think
> request_threaded_irq() without IRQF_ONESHOT would succeed.
> 
> Can someone test the change to be sure?
> 

I can try to test it in a couple of weeks, I don't have the hardware
at hand right now.

Ciao,
   Antonio

-- 
Antonio Ospite
http://ao2.it

A: Because it messes up the order in which people normally read text.
   See http://en.wikipedia.org/wiki/Posting_style
Q: Why is top-posting such a bad thing?
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