Commit-ID: 11df6dddcbc38affb7473aad3d962baf8414a947
Gitweb: http://git.kernel.org/tip/11df6dddcbc38affb7473aad3d962baf8414a947
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Wed, 28 Oct 2009 20:26:48 +0100
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Wed, 28 Oct 2009 20:34:34 +0100
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@xxxxxxxxxx>
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@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Eric Dumazet <eric.dumazet@xxxxxxxxx>
Cc: John Stultz <johnstul@xxxxxxxxxxxxxxxxxx>
Cc: Dinakar Guniguntala <dino@xxxxxxxxxx>
LKML-Reference: <4AE23C74.1090502@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
kernel/futex.c | 6 +-----
1 files changed, 1 insertions(+), 5 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index 642f3bb..fb65e82 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);
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|