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| author | Thomas Gleixner <tglx@linutronix.de> | 2009-10-28 20:26:48 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-10-28 20:34:34 +0100 |
| commit | 11df6dddcbc38affb7473aad3d962baf8414a947 (patch) | |
| tree | fb05ef2583a55e69897988491522b92137ca5f26 | |
| parent | 89061d3d58e1f0742139605dc6a7950aa1ecc019 (diff) | |
| download | linux-11df6dddcbc38affb7473aad3d962baf8414a947.tar.bz2 | |
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>
| -rw-r--r-- | kernel/futex.c | 6 |
1 files changed, 1 insertions, 5 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 642f3bbaacc7..fb65e822fc41 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); |