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| author | Davidlohr Bueso <dave@stgolabs.net> | 2015-06-30 08:26:01 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2015-07-20 11:45:45 +0200 |
| commit | 767f509ca11269c2bcd92e3972a93096f2173ac0 (patch) | |
| tree | be50b83ff9b46f6f5ed97b197d11b5128392cc6d /kernel/futex.c | |
| parent | locking/qrwlock: Better optimization for interrupt context readers (diff) | |
| download | linux-767f509ca11269c2bcd92e3972a93096f2173ac0.tar.xz linux-767f509ca11269c2bcd92e3972a93096f2173ac0.zip | |
futex: Enhance comments in futex_lock_pi() for blocking paths
... 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>
Diffstat (limited to 'kernel/futex.c')
| -rw-r--r-- | kernel/futex.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/kernel/futex.c b/kernel/futex.c index c4a182f5357e..153eb22b0fc0 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2268,8 +2268,11 @@ static long futex_wait_restart(struct restart_block *restart) /* * Userspace tried a 0 -> TID atomic transition of the futex value * 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 - * races the kernel might see a 0 value of the futex too.) + * if there are waiters then it will block as a consequence of relying + * 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, 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); if (unlikely(ret)) { + /* + * Atomic work succeeded and we got the lock, + * or failed. Either way, we do _not_ block. + */ switch (ret) { case 1: /* We got the lock. */ |