linux-kernel - Re: [Linuxarm] Re: [PATCH for next v1 1/2] gpio: omap: Replace raw_spin_lock_irqsave with raw_spin_lock in omap_gpio_irq

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Date:   Fri, 12 Feb 2021 12:27:47 +0200
From:   Grygorii Strashko <grygorii.strashko@...com>
To:     Arnd Bergmann <arnd@...nel.org>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
CC:     luojiaxing <luojiaxing@...wei.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Santosh Shilimkar <ssantosh@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linuxarm@...neuler.org" <linuxarm@...neuler.org>
Subject: Re: [Linuxarm] Re: [PATCH for next v1 1/2] gpio: omap: Replace
 raw_spin_lock_irqsave with raw_spin_lock in omap_gpio_irq_handler()

Hi Arnd,

On 12/02/2021 11:45, Arnd Bergmann wrote:
> On Fri, Feb 12, 2021 at 6:05 AM Song Bao Hua (Barry Song)
> <song.bao.hua@...ilicon.com> wrote:
>>> -----Original Message-----
> 
>>>
>>> Note. there is also generic_handle_irq() call inside.
>>
>> So generic_handle_irq() is not safe to run in thread thus requires
>> an interrupt-disabled environment to run? If so, I'd rather this
>> irqsave moved into generic_handle_irq() rather than asking everyone
>> calling it to do irqsave.
> 
> In a preempt-rt kernel, interrupts are run in task context, so they clearly
> should not be called with interrupts disabled, that would defeat the
> purpose of making them preemptible.
> 
> generic_handle_irq() does need to run with in_irq()==true though,
> but this should be set by the caller of the gpiochip's handler, and
> it is not set by raw_spin_lock_irqsave().

It will produce warning from __handle_irq_event_percpu(), as this is IRQ dispatcher
and generic_handle_irq() will call one of handle_level_irq or handle_edge_irq.

The history behind this is commit 450fa54cfd66 ("gpio: omap: convert to use generic irq handler").

The resent related discussion:
https://lkml.org/lkml/2020/12/5/208



-- 
Best regards,
grygorii