RE: [Linuxarm] Re: [PATCH for-next 00/32] spin lock usage optimization for SCSI drivers

Finn Thain
2021-02-10T04:17:10Z

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

> > > 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 Is the comment in sonic_interrupt() outdated according to this: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
> 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.

> and this:
> genirq: Warn when handler enables interrupts
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b738a50a
>
> 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.

> >
> > Thanks
> > Barry
>
> Thanks
> Barry
>
>