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| author | Peter Zijlstra <peterz@infradead.org> | 2016-04-04 10:57:12 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-06-14 11:54:27 +0200 |
| commit | 1f03e8d2919270bd6ef64f39a45ce8df8a9f012a (patch) | |
| tree | 0cdd5de370212a021d0a1a3439bbc4b0a77fea8b /kernel/sched | |
| parent | 245050c287a9176cee9f98109df101909c1eeef4 (diff) | |
| download | linux-0-day-1f03e8d2919270bd6ef64f39a45ce8df8a9f012a.tar.gz linux-0-day-1f03e8d2919270bd6ef64f39a45ce8df8a9f012a.tar.xz | |
locking/barriers: Replace smp_cond_acquire() with smp_cond_load_acquire()
This new form allows using hardware assisted waiting.
Some hardware (ARM64 and x86) allow monitoring an address for changes,
so by providing a pointer we can use this to replace the cpu_relax()
with hardware optimized methods in the future.
Requested-by: Will Deacon <will.deacon@arm.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/core.c | 8 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 2 |
2 files changed, 5 insertions, 5 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 017d5394f5dc9..5cd6931cb2cb4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1935,7 +1935,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * chain to provide order. Instead we do: * * 1) smp_store_release(X->on_cpu, 0) - * 2) smp_cond_acquire(!X->on_cpu) + * 2) smp_cond_load_acquire(!X->on_cpu) * * Example: * @@ -1946,7 +1946,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * sched-out X * smp_store_release(X->on_cpu, 0); * - * smp_cond_acquire(!X->on_cpu); + * smp_cond_load_acquire(&X->on_cpu, !VAL); * X->state = WAKING * set_task_cpu(X,2) * @@ -1972,7 +1972,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) * This means that any means of doing remote wakeups must order the CPU doing * the wakeup against the CPU the task is going to end up running on. This, * however, is already required for the regular Program-Order guarantee above, - * since the waking CPU is the one issueing the ACQUIRE (smp_cond_acquire). + * since the waking CPU is the one issueing the ACQUIRE (smp_cond_load_acquire). * */ @@ -2045,7 +2045,7 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) * This ensures that tasks getting woken will be fully ordered against * their previous state and preserve Program Order. */ - smp_cond_acquire(!p->on_cpu); + smp_cond_load_acquire(&p->on_cpu, !VAL); p->sched_contributes_to_load = !!task_contributes_to_load(p); p->state = TASK_WAKING; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 72f1f3087b04a..425bf5ddaa5a0 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1113,7 +1113,7 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev) * In particular, the load of prev->state in finish_task_switch() must * happen before this. * - * Pairs with the smp_cond_acquire() in try_to_wake_up(). + * Pairs with the smp_cond_load_acquire() in try_to_wake_up(). */ smp_store_release(&prev->on_cpu, 0); #endif |