Re: [PATCH 4.9.y 1/1] futex: Fix OWNER_DEAD fixup
From: Lee Jones
Date: Wed Feb 24 2021 - 06:20:38 EST
On 2021年2月23日, 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>
Why have you dropped my Reviewed-by?
>
---
>
kernel/futex.c | 6 +++---
>
1 file changed, 3 insertions(+), 3 deletions(-)
>
>
diff --git a/kernel/futex.c b/kernel/futex.c
>
index b65dbb5d60bb..604d1cb9839d 100644
>
--- a/kernel/futex.c
>
+++ b/kernel/futex.c
>
@@ -2424,9 +2424,6 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
>
int err = 0;
>
>
oldowner = pi_state->owner;
>
- /* Owner died? */
>
- if (!pi_state->owner)
>
- newtid |= FUTEX_OWNER_DIED;
>
>
/*
>
* We are here because either:
>
@@ -2484,6 +2481,9 @@ static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
>
}
>
>
newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
>
+ /* Owner died? */
>
+ if (!pi_state->owner)
>
+ newtid |= FUTEX_OWNER_DIED;
>
>
if (get_futex_value_locked(&uval, uaddr))
>
goto handle_fault;
--
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
Follow Linaro: Facebook | Twitter | Blog