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

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Date:   Tue, 30 Aug 2022 13:35:07 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     tuo cao <91tuocao@...il.com>
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

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 :(

And have you measured the time difference?  Is it a real thing?

> 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.

good luck!

greg k-h