linux-kernel - Re: [RESEND] serial: 8250_bcm7271: move spin_lock_irqsave to spin

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Date:   Sun, 4 Sep 2022 16:48:13 +0800
From:   tuo cao <91tuocao@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     alcooperx@...il.com, bcm-kernel-feedback-list@...adcom.com,
        jirislaby@...nel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RESEND] serial: 8250_bcm7271: move spin_lock_irqsave to
 spin_lock in interrupt handler

Greg KH <gregkh@...uxfoundation.org> 于2022年8月30日周二 19:35写道：
>
> On Sat, Aug 27, 2022 at 05:42:19PM +0800, tuo cao wrote:
> > No, whether it's spin_lock_irqsave() or spin_lock(), the security is
> > the same. Since this commit:e58aa3d2d0cc01ad8d6f7f640a0670433f794922,
> > interrupt nesting is disabled, which means interrupts has disabled in
> > the interrupt handlers. So, it is unnecessary to call
> > spin_lock_irqsave in a interrupt handler. And it takes less time
> > obviously to use spin_lock()，so I think this change is needed.
>
> I have no context at all here, please never top-post :(
>
Sorry for causing you trouble. It should be OK this time.

> And have you measured the time difference?  Is it a real thing?
>
Yes, sir. I have measured it, it is a read thing. The test code and
log have been put on Github, please check:
https://github.com/tuocao1991/api_test

> > Finally, I'm sorry I lacked real hardware to verify it and can't
> > provide changelog text.
>
> Try to never do changes for drivers for functionality like this where
> you do not have the hardware to test for, until you get a lot more
> experience.
>
I got it, thanks

> good luck!
>
> greg k-h

Best Regards!