[tip:core/futexes] futex: remove the pointer math from double_unlock_hb, fix

[Ingo Molnar]

Commit-ID:  88f502fedba82eff252b6420e8b8328e4ae25c67
Gitweb:     http://git.kernel.org/tip/88f502fedba82eff252b6420e8b8328e4ae25c67
Author:     Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Fri, 13 Mar 2009 10:32:07 +0100
Commit:     Ingo Molnar <mingo@xxxxxxx>
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.

Reported-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Darren Hart <dvhltc@xxxxxxxxxx>
LKML-Reference: <20090312221118.11146.68610.stgit@Aeon>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>


---
 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);
 }
 
 /*
--
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