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authorThomas Gleixner <tglx@linutronix.de>2009-10-28 20:26:48 +0100
committerThomas Gleixner <tglx@linutronix.de>2009-10-28 20:34:34 +0100
commit11df6dddcbc38affb7473aad3d962baf8414a947 (patch)
treefb05ef2583a55e69897988491522b92137ca5f26 /kernel
parent89061d3d58e1f0742139605dc6a7950aa1ecc019 (diff)
futex: Fix spurious wakeup for requeue_pi really
The requeue_pi path doesn't use unqueue_me() (and the racy lock_ptr == NULL test) nor does it use the wake_list of futex_wake() which where the reason for commit 41890f2 (futex: Handle spurious wake up) See debugging discussing on LKML Message-ID: <4AD4080C.20703@us.ibm.com> The changes in this fix to the wait_requeue_pi path were considered to be a likely unecessary, but harmless safety net. But it turns out that due to the fact that for unknown $@#!*( reasons EWOULDBLOCK is defined as EAGAIN we built an endless loop in the code path which returns correctly EWOULDBLOCK. Spurious wakeups in wait_requeue_pi code path are unlikely so we do the easy solution and return EWOULDBLOCK^WEAGAIN to user space and let it deal with the spurious wakeup. Cc: Darren Hart <dvhltc@us.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Eric Dumazet <eric.dumazet@gmail.com> Cc: John Stultz <johnstul@linux.vnet.ibm.com> Cc: Dinakar Guniguntala <dino@in.ibm.com> LKML-Reference: <4AE23C74.1090502@us.ibm.com> Cc: stable@kernel.org Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/futex.c6
1 files changed, 1 insertions, 5 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 642f3bbaacc..fb65e822fc4 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2127,7 +2127,7 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb,
plist_del(&q->list, &q->list.plist);
/* Handle spurious wakeups gracefully */
- ret = -EAGAIN;
+ ret = -EWOULDBLOCK;
if (timeout && !timeout->task)
ret = -ETIMEDOUT;
else if (signal_pending(current))
@@ -2208,7 +2208,6 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared,
debug_rt_mutex_init_waiter(&rt_waiter);
rt_waiter.task = NULL;
-retry:
key2 = FUTEX_KEY_INIT;
ret = get_futex_key(uaddr2, fshared, &key2, VERIFY_WRITE);
if (unlikely(ret != 0))
@@ -2303,9 +2302,6 @@ out_put_keys:
out_key2:
put_futex_key(fshared, &key2);
- /* Spurious wakeup ? */
- if (ret == -EAGAIN)
- goto retry;
out:
if (to) {
hrtimer_cancel(&to->timer);