-----Original Message-----
From: Finn Thain [mailto:fthain@telegraphics.com.au]
Sent: Wednesday, February 10, 2021 5:16 PM
To: Song Bao Hua (Barry Song) <redacted>
Cc: tanxiaofei <redacted>; jejb@linux.ibm.com;
martin.petersen@oracle.com; linux-scsi@vger.kernel.org;
linux-kernel@vger.kernel.org; linuxarm@openeuler.org;
linux-m68k@vger.kernel.org
Subject: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization
for SCSI drivers

On Tue, 9 Feb 2021, Song Bao Hua (Barry Song) wrote:

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sonic_interrupt() uses an irq lock within an interrupt handler to
avoid issues relating to this. This kind of locking may be needed in
the drivers you are trying to patch. Or it might not. Apparently,
no-one has looked.

Is the comment in sonic_interrupt() outdated according to this:
m68k: irq: Remove IRQF_DISABLED

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
?id=77a4279

quoted

http://lkml.iu.edu/hypermail/linux/kernel/1109.2/01687.html

The removal of IRQF_DISABLED isn't relevant to this driver. Commit
77a42796786c ("m68k: Remove deprecated IRQF_DISABLED") did not disable
interrupts, it just removed some code to enable them.

The code and comments in sonic_interrupt() are correct. You can confirm
this for yourself quite easily using QEMU and a cross-compiler.

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and this:
genirq: Warn when handler enables interrupts

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/
?id=b738a50a

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wouldn't genirq report a warning on m68k?

There is no warning from m68k builds. That's because arch_irqs_disabled()
returns true when the IPL is non-zero.

So for m68k, the case is
arch_irqs_disabled() is true, but interrupts can still come?

Then it seems it is very confusing. If prioritized interrupts can still come
while arch_irqs_disabled() is true, how could spin_lock_irqsave() block the
prioritized interrupts? Isn't arch_irqs_disabled() a status reflection of
irq disable API?

Thanks
Barry