Messages in this thread Patch in this message |  | | | From | Darren Hart <> | | Subject | [PATCH 6/6] futex: Add aggressive adaptive spinning argument to FUTEX_LOCK | | Date | Mon, 5 Apr 2010 13:23:59 -0700 |
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Aggresive adaptive spinning (aas) allows for more than spinner in the adaptive loop at a given time. In some scenarios this yields better results than the default single spinner mode.
Signed-off-by: Darren Hart <dvhltc@us.ibm.com> --- kernel/futex.c | 21 ++++++++++++++++++--- 1 files changed, 18 insertions(+), 3 deletions(-) diff --git a/kernel/futex.c b/kernel/futex.c index af61dcd..ddbd158 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -2462,6 +2462,9 @@ static int trylock_futex_adaptive(u32 __user *uaddr, ktime_t *timeout) * @flags: futex flags (FLAGS_SHARED, FLAGS_CLOCKRT, FLAGS_ADAPTIVE, etc.) * @detect: detect deadlock (1) or not (0) * @time: absolute timeout + * @aas: aggressive adaptive spinning (1) allow multiple spinners (0) allow + * only one spinner. Only valid in conjunction with the FLAGS_ADAPTIVE + * flag. * * futex_(un)lock() define a futex value policy and implement a full mutex. The * futex value stores the owner's TID or'd with FUTEX_WAITERS and/or @@ -2476,12 +2479,14 @@ static int trylock_futex_adaptive(u32 __user *uaddr, ktime_t *timeout) * 0 - On success * <0 - On error */ -static int futex_lock(u32 __user *uaddr, int flags, int detect, ktime_t *time) +static int futex_lock(u32 __user *uaddr, int flags, int detect, ktime_t *time, + int aas) { struct hrtimer_sleeper timeout, *to = NULL; - struct futex_hash_bucket *hb; struct futex_q q = FUTEX_Q_INIT; + struct futex_hash_bucket *hb; int ret = 0; + u32 uval; if (refill_pi_state_cache()) return -ENOMEM; @@ -2497,6 +2502,14 @@ static int futex_lock(u32 __user *uaddr, int flags, int detect, ktime_t *time) retry: #ifdef CONFIG_SMP if (flags & FLAGS_ADAPTIVE) { + if (!aas) { + ret = get_user(uval, uaddr); + if (ret) + goto out; + if (uval & FUTEX_WAITERS) + goto skip_adaptive; + } + preempt_disable(); ret = trylock_futex_adaptive(uaddr, time); preempt_enable(); @@ -2512,6 +2525,8 @@ retry: goto out; } #endif + +skip_adaptive: q.key = FUTEX_KEY_INIT; ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &q.key); if (unlikely(ret != 0)) @@ -2852,7 +2867,7 @@ long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout, flags |= FLAGS_ADAPTIVE; case FUTEX_LOCK: if (futex_cmpxchg_enabled) - ret = futex_lock(uaddr, flags, val, timeout); + ret = futex_lock(uaddr, flags, val, timeout, val3); break; default: ret = -ENOSYS; -- 1.6.3.3
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