linux-kernel - Re: [PATCH 1/3] arm: Fix flush_dcache

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Message-Id: <3e131821-7665-47f0-a8a6-44b3e4d7a88a@app.fastmail.com>
Date:   Wed, 24 May 2023 22:00:14 +0200
From:   "Arnd Bergmann" <arnd@...db.de>
To:     "Helge Deller" <deller@....de>,
        "Russell King" <linux@...linux.org.uk>,
        "Dinh Nguyen" <dinguyen@...nel.org>, linux-kernel@...r.kernel.org,
        linux-parisc@...r.kernel.org
Cc:     linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 1/3] arm: Fix flush_dcache_page() for usage from irq context

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@...linux.org.uk>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: linux-arm-kernel@...ts.infradead.org
> Signed-off-by: Helge Deller <deller@....de>

Cc: stable@...r.kernel.org
Reviewed-by: Arnd Bergmann <arnd@...db.de>

>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