From 013fdb8086acaae5f8eb96f9ad48fcd98882ac46 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 5 Apr 2011 17:23:45 +0200 Subject: [PATCH] sched: Serialize p->cpus_allowed and ttwu() using p->pi_lock Currently p->pi_lock already serializes p->sched_class, also put p->cpus_allowed and try_to_wake_up() under it, this prepares the way to do the first part of ttwu() without holding rq->lock. By having p->sched_class and p->cpus_allowed serialized by p->pi_lock, we prepare the way to call select_task_rq() without holding rq->lock. Reviewed-by: Frank Rowand Signed-off-by: Peter Zijlstra Cc: Mike Galbraith Cc: Nick Piggin Cc: Linus Torvalds Cc: Andrew Morton Link: http://lkml.kernel.org/r/20110405152728.990364093@chello.nl Signed-off-by: Ingo Molnar --- kernel/sched.c | 37 ++++++++++++++++--------------------- 1 file changed, 16 insertions(+), 21 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index dece28e505c..d398f2f0a3c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2340,7 +2340,7 @@ EXPORT_SYMBOL_GPL(kick_process); #ifdef CONFIG_SMP /* - * ->cpus_allowed is protected by either TASK_WAKING or rq->lock held. + * ->cpus_allowed is protected by both rq->lock and p->pi_lock */ static int select_fallback_rq(int cpu, struct task_struct *p) { @@ -2373,7 +2373,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p) } /* - * The caller (fork, wakeup) owns TASK_WAKING, ->cpus_allowed is stable. + * The caller (fork, wakeup) owns p->pi_lock, ->cpus_allowed is stable. */ static inline int select_task_rq(struct rq *rq, struct task_struct *p, int sd_flags, int wake_flags) @@ -2499,7 +2499,8 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state, this_cpu = get_cpu(); smp_wmb(); - rq = task_rq_lock(p, &flags); + raw_spin_lock_irqsave(&p->pi_lock, flags); + rq = __task_rq_lock(p); if (!(p->state & state)) goto out; @@ -2557,7 +2558,8 @@ out_running: ttwu_stat(rq, p, cpu, wake_flags); success = 1; out: - task_rq_unlock(rq, &flags); + __task_rq_unlock(rq); + raw_spin_unlock_irqrestore(&p->pi_lock, flags); put_cpu(); return success; @@ -4694,6 +4696,8 @@ void rt_mutex_setprio(struct task_struct *p, int prio) BUG_ON(prio < 0 || prio > MAX_PRIO); + lockdep_assert_held(&p->pi_lock); + rq = task_rq_lock(p, &flags); trace_sched_pi_setprio(p, prio); @@ -5317,7 +5321,6 @@ long sched_getaffinity(pid_t pid, struct cpumask *mask) { struct task_struct *p; unsigned long flags; - struct rq *rq; int retval; get_online_cpus(); @@ -5332,9 +5335,9 @@ long sched_getaffinity(pid_t pid, struct cpumask *mask) if (retval) goto out_unlock; - rq = task_rq_lock(p, &flags); + raw_spin_lock_irqsave(&p->pi_lock, flags); cpumask_and(mask, &p->cpus_allowed, cpu_online_mask); - task_rq_unlock(rq, &flags); + raw_spin_unlock_irqrestore(&p->pi_lock, flags); out_unlock: rcu_read_unlock(); @@ -5882,18 +5885,8 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) unsigned int dest_cpu; int ret = 0; - /* - * Serialize against TASK_WAKING so that ttwu() and wunt() can - * drop the rq->lock and still rely on ->cpus_allowed. - */ -again: - while (task_is_waking(p)) - cpu_relax(); - rq = task_rq_lock(p, &flags); - if (task_is_waking(p)) { - task_rq_unlock(rq, &flags); - goto again; - } + raw_spin_lock_irqsave(&p->pi_lock, flags); + rq = __task_rq_lock(p); if (!cpumask_intersects(new_mask, cpu_active_mask)) { ret = -EINVAL; @@ -5921,13 +5914,15 @@ again: if (migrate_task(p, rq)) { struct migration_arg arg = { p, dest_cpu }; /* Need help from migration thread: drop lock and wait. */ - task_rq_unlock(rq, &flags); + __task_rq_unlock(rq); + raw_spin_unlock_irqrestore(&p->pi_lock, flags); stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); tlb_migrate_finish(p->mm); return 0; } out: - task_rq_unlock(rq, &flags); + __task_rq_unlock(rq); + raw_spin_unlock_irqrestore(&p->pi_lock, flags); return ret; } -- 2.20.1