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

From: Helge Deller
Date: Wed May 24 2023 - 16:57:01 EST

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>

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

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.