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futex: Enhance comments in futex_lock_pi() for blocking paths

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... serves a bit better to clarify between blocking
and non-blocking code paths.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Darren Hart <darren@dvhart.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Link: http://lkml.kernel.org/r/1435645562-975-2-git-send-email-dave@stgolabs.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Davidlohr Bueso 2015-06-29 23:26:01 -07:00 committed by Thomas Gleixner
parent 0e06e5be70
commit 767f509ca1
1 changed files with 9 additions and 2 deletions
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11
kernel/futex.c
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@ -2268,8 +2268,11 @@ static long futex_wait_restart(struct restart_block *restart)
/* /*
* Userspace tried a 0 -> TID atomic transition of the futex value * Userspace tried a 0 -> TID atomic transition of the futex value
* and failed. The kernel side here does the whole locking operation: * and failed. The kernel side here does the whole locking operation:
* if there are waiters then it will block, it does PI, etc. (Due to * if there are waiters then it will block as a consequence of relying
* races the kernel might see a 0 value of the futex too.) * on rt-mutexes, it does PI, etc. (Due to races the kernel might see
* a 0 value of the futex too.).
*
* Also serves as futex trylock_pi()'ing, and due semantics.
*/ */
static int futex_lock_pi(u32 __user *uaddr, unsigned int flags, static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
ktime_t *time, int trylock) ktime_t *time, int trylock)
@ -2300,6 +2303,10 @@ retry_private:
ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0); ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current, 0);
if (unlikely(ret)) { if (unlikely(ret)) {
/*
* Atomic work succeeded and we got the lock,
* or failed. Either way, we do _not_ block.
*/
switch (ret) { switch (ret) {
case 1: case 1:
/* We got the lock. */ /* We got the lock. */