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SubjectRe: [PATCH 4.9.y 1/1] futex: Fix OWNER_DEAD fixup
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On 2021/2/25 16:09, Lee Jones wrote:
> On Thu, 25 Feb 2021, Zhengyejian (Zetta) wrote:
>
>>
>>
>> On 2021/2/24 19:19, Lee Jones wrote:
>>> On Tue, 23 Feb 2021, Zheng Yejian wrote:
>>>
>>>> From: Peter Zijlstra <peterz@infradead.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@linux-m68k.org>
>>>> Reported-by: Dave Jones <davej@codemonkey.org.uk>
>>>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>>>> Cc: Andrew Morton <akpm@linux-foundation.org>
>>>> Cc: Linus Torvalds <torvalds@linux-foundation.org>
>>>> Cc: Paul E. McKenney <paulmck@us.ibm.com>
>>>> Cc: Peter Zijlstra <peterz@infradead.org>
>>>> Cc: Thomas Gleixner <tglx@linutronix.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@kernel.org>
>>>> Signed-off-by: Zheng Yejian <zhengyejian1@huawei.com>
>>>
>>> Why have you dropped my Reviewed-by?
>>>
>> Really sorry. I thought that a changed patchset needs another review.
>> Then I do need to append your Reviewed-by and send a "V2" patchset, Do I?
>
> No need. I won't hold up merging just for that.
>
> Just bear in mind that you should apply and carry forward *-by tags
> unless there have been significant/functional changes.
>
> Reviewed-by: Lee Jones <lee.jones@linaro.org>
>

I get it, thanks.

>>>> ---
>>>> 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;
>>>
>

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