On Thu, 23 Mar 2017, Julia Cartwright wrote:
> On Thu, Mar 23, 2017 at 10:26:49AM +0000, Lee Jones wrote:
> > On Thu, 23 Mar 2017, Lionel DEBIEVE wrote:
> >
> > > On 03/22/2017 07:47 PM, Julia Cartwright wrote:
> > > > On Wed, Mar 22, 2017 at 01:30:12PM -0500, Grygorii Strashko wrote:
> > > >> On 03/22/2017 01:01 PM, Steven Rostedt wrote:
> > > >>> On Wed, 22 Mar 2017 12:37:59 -0500
> > > >>> Julia Cartwright <julia@xxxxxx> wrote:
> > > >>>
> > > >>>> Which kernel were you testing on, here? From what I can tell, this
> > > >>>> should have been fixed with Thomas's commit:
> > > >>>>
> > > >>>> 2a1d3ab8986d ("genirq: Handle force threading of irqs with primary
> > > >>>> and thread handler")
> > > >>> Thanks Julia for looking into this. I just looked at the code, and saw
> > > >>> that it does very little with the lock held, and was fine with the
> > > >>> conversion. But if that interrupt handler should be in a thread, we
> > > >>> should see if that's the issue first.
> > > >>
> > > >> It will not be threaded because there are IRQF_ONESHOT used.
> > > >>
> > > >> ret = devm_request_threaded_irq(&pdev->dev, irq,
> > > >> sti_mbox_irq_handler,
> > > >> sti_mbox_thread_handler,
> > > >> IRQF_ONESHOT, mdev->name, mdev);
> > > > Indeed. I had skipped over this important detail when I was skimming
> > > > through the code.
> > > >
> > > > Thanks for clarifying!
> > > >
> > > > Is IRQF_ONESHOT really necessary for this device? The primary handler
> > > > invokes sti_mbox_disable_channel() on the interrupting channel, which I
> > > > would hope would acquiesce the pending interrupt at the device-level?
> >
> > Not sure. This part of the code is remanent from when I re-wrote it.
> >
> > What is the alternative?
>
> If, on the completed execution of the registered primary handler, you
> can ensure that the device is no longer asserting an interrupt to the
> connected irq chip, then the IRQF_ONESHOT isn't necessary, because it's
> safe for the irq core to unmask the interrupt after the primary handler
> runs.
>
> It appears that it might be able to make this guarantee, if that's what
> sti_mbox_disable_channel() is doing.
Yes, I'm inclined to agree.
> > NB: What does 'acquiesce' mean in this context? Is that a typo?
>
> I mean 'acquiesce' to mean what I mention before: prevent the device
> from asserting the interrupt. Perhaps it's a uncommon use of the word.
http://www.thesaurus.com/browse/acquiesce
Perhaps 'suppress' or 'quell' would better suit the situation.
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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