From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: luojiaxing <luojiaxing@huawei.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Grygorii Strashko <grygorii.strashko@ti.com>,
Santosh Shilimkar <ssantosh@kernel.org>,
Kevin Hilman <khilman@kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
linuxarm@openeuler.org
Subject: Re: [Linuxarm] [PATCH for next v1 0/2] gpio: few clean up patches to replace spin_lock_irqsave with spin_lock
Date: Tue, 9 Feb 2021 11:42:05 +0200 [thread overview]
Message-ID: <CAHp75Vd5UV3E79sdq8uQ4pgjFORdJknpm-g7No3tomnKhinMnw@mail.gmail.com> (raw)
In-Reply-To: <1a5dfcf2-11a2-f549-782d-447d58e21305@huawei.com>
On Tue, Feb 9, 2021 at 11:24 AM luojiaxing <luojiaxing@huawei.com> wrote:
> On 2021/2/8 21:28, Andy Shevchenko wrote:
> > On Mon, Feb 8, 2021 at 11:11 AM luojiaxing <luojiaxing@huawei.com> wrote:
> >> Sorry, my operation error causes a patch missing from this patch set. I
> >> re-send the patch set. Please check the new one.
> > What is the new one?! You have to give proper versioning and change
> > log for your series.
>
> sure, I will send a new one later, but let me answer your question first.
>
> >> On 2021/2/8 16:56, Luo Jiaxing wrote:
> >>> There is no need to use API with _irqsave in hard IRQ handler, So replace
> >>> those with spin_lock.
> > How do you know that another CPU in the system can't serve the
The keyword here is: *another*.
> > following interrupt from the hardware at the same time?
>
> Yes, I have some question before.
>
> There are some similar discussion here, please take a look, Song baohua
> explained it more professionally.
>
> https://lore.kernel.org/lkml/e949a474a9284ac6951813bfc8b34945@hisilicon.com/
>
> Here are some excerpts from the discussion:
>
> I think the code disabling irq in hardIRQ is simply wrong.
Why?
> Since this commit
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=e58aa3d2d0cc
> genirq: Run irq handlers with interrupts disabled
>
> interrupt handlers are definitely running in a irq-disabled context
> unless irq handlers enable them explicitly in the handler to permit
> other interrupts.
This doesn't explain any changes in the behaviour on SMP.
IRQ line can be disabled on a few stages:
a) on the source (IP that generates an event)
b) on IRQ router / controller
c) on CPU side
The commit above is discussing (rightfully!) the problem when all
interrupts are being served by a *single* core. Nobody prevents them
from being served by *different* cores simultaneously. Also, see [1].
[1]: https://www.kernel.org/doc/htmldocs/kernel-locking/cheatsheet.html
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2021-02-09 9:44 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-08 8:56 [PATCH for next v1 0/2] gpio: few clean up patches to replace spin_lock_irqsave with spin_lock Luo Jiaxing
2021-02-08 8:56 ` [PATCH for next v1 1/2] gpio: omap: Replace raw_spin_lock_irqsave with raw_spin_lock in omap_gpio_irq_handler() Luo Jiaxing
2021-02-11 18:14 ` Grygorii Strashko
2021-02-11 19:39 ` Arnd Bergmann
2021-02-11 20:16 ` Grygorii Strashko
[not found] ` <a61ef337fd1c4538a47fe855920f95d3@hisilicon.com>
[not found] ` <CAK8P3a3SHQNjF5ZpqHQweG7BQ52Xi1hQKDiMVKq4aNK_7VDw6w@mail.gmail.com>
2021-02-12 10:27 ` [Linuxarm] " Grygorii Strashko
2021-02-12 10:42 ` Song Bao Hua (Barry Song)
2021-02-12 10:57 ` Andy Shevchenko
2021-02-12 11:29 ` Song Bao Hua (Barry Song)
2021-02-12 11:53 ` Grygorii Strashko
2021-02-12 13:12 ` Song Bao Hua (Barry Song)
2021-02-12 14:08 ` Grygorii Strashko
2021-02-12 20:06 ` Song Bao Hua (Barry Song)
2021-02-12 20:23 ` Arnd Bergmann
2021-02-12 20:49 ` Song Bao Hua (Barry Song)
2021-02-12 10:59 ` Arnd Bergmann
2021-02-12 11:35 ` Andy Shevchenko
2021-02-08 9:11 ` [Linuxarm] [PATCH for next v1 0/2] gpio: few clean up patches to replace spin_lock_irqsave with spin_lock luojiaxing
2021-02-08 13:28 ` Andy Shevchenko
2021-02-09 9:24 ` luojiaxing
2021-02-09 9:42 ` Andy Shevchenko [this message]
2021-02-10 3:43 ` luojiaxing
2021-02-10 10:50 ` Andy Shevchenko
2021-02-10 11:50 ` [Linuxarm] " Song Bao Hua (Barry Song)
2021-02-10 14:56 ` Andy Shevchenko
2021-02-10 20:42 ` Song Bao Hua (Barry Song)
2021-02-11 9:58 ` Andy Shevchenko
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