From 89061d3d58e1f0742139605dc6a7950aa1ecc019 Mon Sep 17 00:00:00 2001 From: Darren Hart Date: Thu, 15 Oct 2009 15:30:48 -0700 Subject: [PATCH] futex: Move drop_futex_key_refs out of spinlock'ed region When requeuing tasks from one futex to another, the reference held by the requeued task to the original futex location needs to be dropped eventually. Dropping the reference may ultimately lead to a call to "iput_final" and subsequently call into filesystem- specific code - which may be non-atomic. It is therefore safer to defer this drop operation until after the futex_hash_bucket spinlock has been dropped. Originally-From: Helge Bahmann Signed-off-by: Darren Hart Cc: Cc: Peter Zijlstra Cc: Eric Dumazet Cc: Dinakar Guniguntala Cc: John Stultz Cc: Sven-Thorsten Dietrich Cc: John Kacur LKML-Reference: <4AD7A298.5040802@us.ibm.com> Signed-off-by: Ingo Molnar --- kernel/futex.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/futex.c b/kernel/futex.c index 06938e560ac9..642f3bbaacc7 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1029,7 +1029,6 @@ static inline void requeue_pi_wake_futex(struct futex_q *q, union futex_key *key, struct futex_hash_bucket *hb) { - drop_futex_key_refs(&q->key); get_futex_key_refs(key); q->key = *key; @@ -1227,6 +1226,7 @@ retry_private: */ if (ret == 1) { WARN_ON(pi_state); + drop_count++; task_count++; ret = get_futex_value_locked(&curval2, uaddr2); if (!ret) @@ -1305,6 +1305,7 @@ retry_private: if (ret == 1) { /* We got the lock. */ requeue_pi_wake_futex(this, &key2, hb2); + drop_count++; continue; } else if (ret) { /* -EDEADLK */