linux-kernel - Re: [PATCH 4.9.257 1/1] futex: Fix OWNER

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Message-ID: <20210222115424.GF376568@dell>
Date:   Mon, 22 Feb 2021 11:54:24 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Zheng Yejian <zhengyejian1@...wei.com>
Cc:     gregkh@...uxfoundation.org, stable@...r.kernel.org,
        linux-kernel@...r.kernel.org, judy.chenhui@...wei.com,
        zhangjinhao2@...wei.com, tglx@...utronix.de
Subject: Re: [PATCH 4.9.257 1/1] futex: Fix OWNER_DEAD fixup

On Mon, 22 Feb 2021, Zheng Yejian wrote:

> From: Peter Zijlstra <peterz@...radead.org>
> 
> commit a97cb0e7b3f4c6297fd857055ae8e895f402f501 upstream.
> 
> Both Geert and DaveJ reported that the recent futex commit:
> 
>   c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
> 
> introduced a problem with setting OWNER_DEAD. We set the bit on an
> uninitialized variable and then entirely optimize it away as a
> dead-store.
> 
> Move the setting of the bit to where it is more useful.
> 
> Reported-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> Reported-by: Dave Jones <davej@...emonkey.org.uk>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Paul E. McKenney <paulmck@...ibm.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
> Link: http://lkml.kernel.org/r/20180122103947.GD2228@hirez.programming.kicks-ass.net
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> Signed-off-by: Zheng Yejian <zhengyejian1@...wei.com>
> ---
>  kernel/futex.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)

Reviewed-by: Lee Jones <lee.jones@...aro.org>

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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