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SubjectRe: [Linuxarm] [PATCH for next v1 0/2] gpio: few clean up patches to replace spin_lock_irqsave with spin_lock
On Tue, Feb 9, 2021 at 11:24 AM luojiaxing <> wrote:
> On 2021/2/8 21:28, Andy Shevchenko wrote:
> > On Mon, Feb 8, 2021 at 11:11 AM luojiaxing <> 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.
> Here are some excerpts from the discussion:
> I think the code disabling irq in hardIRQ is simply wrong.


> Since this commit
> 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].


With Best Regards,
Andy Shevchenko

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