Re: [PATCH] input: pcap2: avoid calling mutex_lock() in irq handler

From: Antonio Ospite
Date: Wed May 21 2014 - 05:18:04 EST


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

Tested-by: Antonio Ospite <ao2@xxxxxx>

I confirm the keys still work fine with the patch applied on a 3.2
kernel. I cannot test on a newer version for now.

Sorry for the delay.

Ciao 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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