Re: [PATCH 1/3] arm: Fix flush_dcache_page() for usage from irq context

[Helge Deller]

On 5/24/23 22:00, Arnd Bergmann wrote:
> On Wed, May 24, 2023, at 17:26, Helge Deller wrote:
> > Since at least kernel 6.1, flush_dcache_page() is called with IRQs
> > disabled, e.g. from aio_complete().
> >
> > But the current implementation for flush_dcache_page() on ARM
> > unintentionally re-enables IRQs, which may lead to deadlocks.
> >
> > Fix it by using xa_lock_irqsave() and xa_unlock_irqrestore()
> > for the flush_dcache_mmap_*lock() macros instead.
> >
> > Cc: Russell King (Oracle) <linux@xxxxxxxxxxxxxxx>
> > Cc: Arnd Bergmann <arnd@xxxxxxxx>
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Signed-off-by: Helge Deller <deller@xxxxxx>
>
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Arnd Bergmann <arnd@xxxxxxxx>

Thanks!
I assume it's picked up in the arm git tree then.

>  From what I can tell, the behavior in aio_complete has been
> there for over 10 years, since 21b40200cfe96 ("aio: use
> flush_dcache_page()").

Oh, then those arches are broken since then.

> Others may have done the same already back then.
>
> I also see you sent patches for nios2 and parisc, but not
> for csky, which appears to need the same thing.

csky doesn't use flush_dcache_mmap_lock() inside it's
flush_dcache_page() function, so I think it's not affected.

Helge