On Wed, 18 Jun 2014, Doug Anderson wrote:
> Lee,
>
> On Wed, Jun 18, 2014 at 12:55 AM, Lee Jones <lee.jones@xxxxxxxxxx> wrote:
> > On Mon, 16 Jun 2014, Doug Anderson wrote:
> >
> >> From: Bill Richardson <wfrichar@xxxxxxxxxxxx>
> >>
> >> Preparing the way for the LPC device, which is just a plaform_device without
> >> interrupts.
> >>
> >> Signed-off-by: Bill Richardson <wfrichar@xxxxxxxxxxxx>
> >> Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> >> ---
> >> drivers/mfd/cros_ec.c | 26 +++++++++++++-------------
> >> 1 file changed, 13 insertions(+), 13 deletions(-)
> >>
> >> diff --git a/drivers/mfd/cros_ec.c b/drivers/mfd/cros_ec.c
> >> index 38fe9bf..bd6f936 100644
> >> --- a/drivers/mfd/cros_ec.c
> >> +++ b/drivers/mfd/cros_ec.c
> >> @@ -119,17 +119,15 @@ int cros_ec_register(struct cros_ec_device *ec_dev)
> >> return -ENOMEM;
> >> }
> >>
> >> - if (!ec_dev->irq) {
> >> - dev_dbg(dev, "no valid IRQ: %d\n", ec_dev->irq);
> >> - return err;
> >> - }
> >> -
> >> - err = request_threaded_irq(ec_dev->irq, NULL, ec_irq_thread,
> >> - IRQF_TRIGGER_LOW | IRQF_ONESHOT,
> >> - "chromeos-ec", ec_dev);
> >> - if (err) {
> >> - dev_err(dev, "request irq %d: error %d\n", ec_dev->irq, err);
> >> - return err;
> >> + if (ec_dev->irq) {
> >> + err = request_threaded_irq(ec_dev->irq, NULL, ec_irq_thread,
> >> + IRQF_TRIGGER_LOW | IRQF_ONESHOT,
> >> + "chromeos-ec", ec_dev);
> >
> > Is there anything stopping you using the devm_* version?
>
> I'm generally quite hesitant about using the devm_ IRQ functions.
> Requesting an IRQ enables the IRQ at the time of request and freeing
> it disables it, right? Leaving it up to the the devm subsystem to
> disable your IRQ tends to be a race waiting to happen if an IRQ
> happens after you've freed all your memory / cleaned up all your
> state.
>
> Looking at cros_ec in particular though:
>
> * Right now the last thing done in cros_ec_remove() (which is the last
> thing in both cros_ec_i2c_remove and cros_ec_spi_remove) is to free
> the IRQ. That means that you're right: we could switch to devm_ in
> this case and it wouldn't introduce any new bugs.
>
> * ...but I'm not convinced that the location of the free_irq() today
> is quite right. I couldn't actually get it to crash or hang, but
> there is a time period where we've called mfd_remove_devices() and the
> IRQ is still active. That doesn't seem like a super great situation
> to be in. I'll add a move of the irq_free to the patch series.
I guess if you're concerned about ordering you could always use
devm_free_irq() in the places where you think it should be freed
earlier than release. I'm pretty sure that discludes the failure
patch in probe() though, so we'd still be able to rid a few lines.
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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