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

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On 2021/2/22 20:36, Greg KH wrote:
On Mon, Feb 22, 2021 at 08:20:38PM +0800, Zhengyejian (Zetta) wrote:


On 2021/2/22 20:07, Greg KH wrote:
On Mon, Feb 22, 2021 at 11:54:24AM +0000, Lee Jones wrote:
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>

This does not apply to the 4.9.y tree at all right now, are you all sure
you got the backport correct?

confused,

greg k-h
.

I make the patch basing on 282aeb477a10 ("Linux 4.9.257").
Should I base on f0cf73f13b39 ("Linux 4.9.258-rc1")?

Yes please as I think this is already there.

How about just waiting for the next release to come out, I will push out
the 4.4 and 4.9 -rc releases right now as well to give everyone a chance
to sync up properly.
Ok, I will rebase this patch then.
Thanks for your suggestion.


thanks,

greg k-h
.




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