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| author | Darren Hart <dvhltc@us.ibm.com> | 2009-07-31 16:20:10 -0700 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-08-04 15:59:14 +0200 |
| commit | cc6db4e60116c1f76577b6850a35ae7de69a95b6 (patch) | |
| tree | 52c2a020429f4664453719483ac3d3d993802330 /kernel/futex.c | |
| parent | a33a052f19a21d727847391c8c1aff3fb221c472 (diff) | |
| download | linux-cc6db4e60116c1f76577b6850a35ae7de69a95b6.tar.gz linux-cc6db4e60116c1f76577b6850a35ae7de69a95b6.tar.bz2 linux-cc6db4e60116c1f76577b6850a35ae7de69a95b6.zip | |
futex: Correct futex_wait_requeue_pi() commentary
The state machine described in the comments wasn't updated with
a follow-on fix. Address that and cleanup the corresponding
commentary in the function.
Signed-off-by: Darren Hart <dvhltc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
LKML-Reference: <4A737C2A.9090001@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 23 |
1 files changed, 10 insertions, 13 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index 0672ff88f159..d077201b393d 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2102,11 +2102,11 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, * We call schedule in futex_wait_queue_me() when we enqueue and return there * via the following: * 1) wakeup on uaddr2 after an atomic lock acquisition by futex_requeue() - * 2) wakeup on uaddr2 after a requeue and subsequent unlock - * 3) signal (before or after requeue) - * 4) timeout (before or after requeue) + * 2) wakeup on uaddr2 after a requeue + * 3) signal + * 4) timeout * - * If 3, we setup a restart_block with futex_wait_requeue_pi() as the function. + * If 3, cleanup and return -ERESTARTNOINTR. * * If 2, we may then block on trying to take the rt_mutex and return via: * 5) successful lock @@ -2114,7 +2114,7 @@ int handle_early_requeue_pi_wakeup(struct futex_hash_bucket *hb, * 7) timeout * 8) other lock acquisition failure * - * If 6, we setup a restart_block with futex_lock_pi() as the function. + * If 6, return -EWOULDBLOCK (restarting the syscall would do the same). * * If 4 or 7, we cleanup and return with -ETIMEDOUT. * @@ -2232,14 +2232,11 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, int fshared, rt_mutex_unlock(pi_mutex); } else if (ret == -EINTR) { /* - * We've already been requeued, but we have no way to - * restart by calling futex_lock_pi() directly. We - * could restart the syscall, but that will look at - * the user space value and return right away. So we - * drop back with EWOULDBLOCK to tell user space that - * "val" has been changed. That's the same what the - * restart of the syscall would do in - * futex_wait_setup(). + * We've already been requeued, but cannot restart by calling + * futex_lock_pi() directly. We could restart this syscall, but + * it would detect that the user space "val" changed and return + * -EWOULDBLOCK. Save the overhead of the restart and return + * -EWOULDBLOCK directly. */ ret = -EWOULDBLOCK; } |