linux-kernel - Re: [PATCH] kgdbts: fix hw_access_break

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Message-ID: <CAD=FV=VC20PvOPSf9quqghA8SKKkCduadtU7nso4wkSwVKH3jQ@mail.gmail.com>
Date: Mon, 12 Aug 2024 13:04:22 -0700
From: Doug Anderson <dianders@...omium.org>
To: Florian Rommel <mail@...rommel.de>
Cc: Jason Wessel <jason.wessel@...driver.com>, 
	Daniel Thompson <daniel.thompson@...aro.org>, Arnd Bergmann <arnd@...db.de>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, kgdb-bugreport@...ts.sourceforge.net, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kgdbts: fix hw_access_break_test

Hi,

On Mon, Aug 12, 2024 at 1:55 AM Florian Rommel <mail@...rommel.de> wrote:
>
> The test for access watchpoints (hw_access_break_test) was broken
> (always failed) because the compiler optimized out the write to the
> static helper variable (hw_break_val2), as it is never read anywhere.
> This resulted in the target variable (hw_break_val) not being accessed
> and thus the breakpoint not being triggered.
>
> Remove the helper variable (hw_break_val2), and use READ_ONCE to force
> reading the target variable (hw_break_val).
>
> Signed-off-by: Florian Rommel <mail@...rommel.de>
> ---
>  drivers/misc/kgdbts.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Douglas Anderson <dianders@...omium.org>