linux-kernel - Re: [PATCH RT 1/1] remoteproc: Prevent schedule while atomic

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Date:   Thu, 23 Mar 2017 10:26:49 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Lionel DEBIEVE <lionel.debieve@...com>
Cc:     Julia Cartwright <julia@...com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Steven Rostedt <rostedt@...dmis.org>,
        "linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bigeasy@...utronix.de" <bigeasy@...utronix.de>,
        "tglx@...utronix.de" <tglx@...utronix.de>
Subject: Re: [PATCH RT 1/1] remoteproc: Prevent schedule while atomic

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@...com> 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?

NB: What does 'acquiesce' mean in this context?  Is that a typo?

> > Also, as written there are num_inst reads of STI_IRQ_VAL_OFFSET in the
> > primary handler, which seems inefficient...(unless of course reading
> > incurs side effects, here).

Inefficient in what respect?

> First to reply Julia, test was made using 4.9.y kernel branch.
> For the IRQF_ONESHOT, I rely on Lee (adding in mail thread) that was at the device driver origin.
> 
> Steven, you're also right as the patch can be also pushed in mainline too.
> 
> Lionel
> 

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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