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

[Arnd Bergmann]

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>

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

     Arnd