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SubjectRe: [tip:core/futexes] futex: remove the pointer math from double_unlock_hb, fix
Ingo Molnar wrote:
> Commit-ID: 88f502fedba82eff252b6420e8b8328e4ae25c67
> Gitweb: http://git.kernel.org/tip/88f502fedba82eff252b6420e8b8328e4ae25c67
> Author: Ingo Molnar <mingo@elte.hu>
> AuthorDate: Fri, 13 Mar 2009 10:32:07 +0100
> Commit: Ingo Molnar <mingo@elte.hu>
> CommitDate: Fri, 13 Mar 2009 10:32:07 +0100
>
> futex: remove the pointer math from double_unlock_hb, fix
>
> Impact: fix double unlock crash
>
> Thomas Gleixner noticed that the simplified double_unlock_hb()
> became ... too unsophisticated: in the hb1 == hb2 case it will
> do a double unlock.

Gah. Thanks for catching it.

>
> Reported-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Darren Hart <dvhltc@us.ibm.com>
> LKML-Reference: <20090312221118.11146.68610.stgit@Aeon>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>

Acked-by: Darren Hart <dvhltc@us.ibm.com>

>
>
> ---
> kernel/futex.c | 3 ++-
> 1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/futex.c b/kernel/futex.c
> index 2331b73..6b50a02 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -659,7 +659,8 @@ static inline void
> double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
> {
> spin_unlock(&hb1->lock);
> - spin_unlock(&hb2->lock);
> + if (hb1 != hb2)
> + spin_unlock(&hb2->lock);
> }
>
> /*


--
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team


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