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authorDarren Hart <dvhltc@us.ibm.com>2009-04-02 14:19:38 -0700
committerIngo Molnar <mingo@elte.hu>2009-04-02 23:39:53 +0200
commitcd84a42f315e50edd454c27a3da3951ccd3d735a (patch)
treefa13b2faa6c2f73255f52a65cd4f572d9bd95e1a
parent833bb3046b6cb320e775ea2160ddca87d53260d5 (diff)
futex: comment requeue key reference semantics
We've tripped over the futex_requeue drop_count refering to key2 instead of key1. The code is actually correct, but is non-intuitive. This patch adds an explicit comment explaining the requeue. Signed-off-by: Darren Hart <dvhltc@us.ibm.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/futex.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 6b50a024bca..eef8cd26b5e 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -883,7 +883,12 @@ retry_private:
out_unlock:
double_unlock_hb(hb1, hb2);
- /* drop_futex_key_refs() must be called outside the spinlocks. */
+ /*
+ * drop_futex_key_refs() must be called outside the spinlocks. During
+ * the requeue we moved futex_q's from the hash bucket at key1 to the
+ * one at key2 and updated their key pointer. We no longer need to
+ * hold the references to key1.
+ */
while (--drop_count >= 0)
drop_futex_key_refs(&key1);