Re: [PATCH 4.9.257 1/1] futex: Fix OWNER_DEAD fixup

[Lee Jones]

On Mon, 22 Feb 2021, Zheng Yejian wrote:

> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxx>
> Reported-by: Dave Jones <davej@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Fixes: c1e2f0eaf015 ("futex: Avoid violating the 10th rule of futex")
> Link: http://lkml.kernel.org/r/20180122103947.GD2228@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> Signed-off-by: Zheng Yejian <zhengyejian1@xxxxxxxxxx>
> ---
>  kernel/futex.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)

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

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