diff options
| -rw-r--r-- | kernel/sched.c | 83 |
1 files changed, 66 insertions, 17 deletions
diff --git a/kernel/sched.c b/kernel/sched.c index e964f2c589c..a56613015df 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2017,21 +2017,15 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p, */ void kthread_bind(struct task_struct *p, unsigned int cpu) { - struct rq *rq = cpu_rq(cpu); - unsigned long flags; - /* Must have done schedule() in kthread() before we set_task_cpu */ if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE)) { WARN_ON(1); return; } - spin_lock_irqsave(&rq->lock, flags); - set_task_cpu(p, cpu); p->cpus_allowed = cpumask_of_cpu(cpu); p->rt.nr_cpus_allowed = 1; p->flags |= PF_THREAD_BOUND; - spin_unlock_irqrestore(&rq->lock, flags); } EXPORT_SYMBOL(kthread_bind); @@ -2072,6 +2066,14 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) struct cfs_rq *old_cfsrq = task_cfs_rq(p), *new_cfsrq = cpu_cfs_rq(old_cfsrq, new_cpu); +#ifdef CONFIG_SCHED_DEBUG + /* + * We should never call set_task_cpu() on a blocked task, + * ttwu() will sort out the placement. + */ + WARN_ON(p->state != TASK_RUNNING && p->state != TASK_WAKING); +#endif + trace_sched_migrate_task(p, new_cpu); if (old_cpu != new_cpu) { @@ -2105,12 +2107,10 @@ migrate_task(struct task_struct *p, int dest_cpu, struct migration_req *req) /* * If the task is not on a runqueue (and not running), then - * it is sufficient to simply update the task's cpu field. + * the next wake-up will properly place the task. */ - if (!p->se.on_rq && !task_running(rq, p)) { - set_task_cpu(p, dest_cpu); + if (!p->se.on_rq && !task_running(rq, p)) return 0; - } init_completion(&req->done); req->task = p; @@ -2316,10 +2316,42 @@ void task_oncpu_function_call(struct task_struct *p, } #ifdef CONFIG_SMP +/* + * Called from: + * + * - fork, @p is stable because it isn't on the tasklist yet + * + * - exec, @p is unstable XXX + * + * - wake-up, we serialize ->cpus_allowed against TASK_WAKING so + * we should be good. + */ static inline int select_task_rq(struct task_struct *p, int sd_flags, int wake_flags) { - return p->sched_class->select_task_rq(p, sd_flags, wake_flags); + int cpu = p->sched_class->select_task_rq(p, sd_flags, wake_flags); + + /* + * In order not to call set_task_cpu() on a blocking task we need + * to rely on ttwu() to place the task on a valid ->cpus_allowed + * cpu. + * + * Since this is common to all placement strategies, this lives here. + * + * [ this allows ->select_task() to simply return task_cpu(p) and + * not worry about this generic constraint ] + */ + if (unlikely(!cpumask_test_cpu(cpu, &p->cpus_allowed) || + !cpu_active(cpu))) { + + cpu = cpumask_any_and(&p->cpus_allowed, cpu_active_mask); + /* + * XXX: race against hot-plug modifying cpu_active_mask + */ + BUG_ON(cpu >= nr_cpu_ids); + } + + return cpu; } #endif @@ -7128,7 +7160,23 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) struct rq *rq; int ret = 0; + /* + * Since we rely on wake-ups to migrate sleeping tasks, don't change + * the ->cpus_allowed mask from under waking tasks, which would be + * possible when we change rq->lock in ttwu(), so synchronize against + * TASK_WAKING to avoid that. + */ +again: + while (p->state == TASK_WAKING) + cpu_relax(); + rq = task_rq_lock(p, &flags); + + if (p->state == TASK_WAKING) { + task_rq_unlock(rq, &flags); + goto again; + } + if (!cpumask_intersects(new_mask, cpu_active_mask)) { ret = -EINVAL; goto out; @@ -7184,7 +7232,7 @@ EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) { struct rq *rq_dest, *rq_src; - int ret = 0, on_rq; + int ret = 0; if (unlikely(!cpu_active(dest_cpu))) return ret; @@ -7200,12 +7248,13 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) if (!cpumask_test_cpu(dest_cpu, &p->cpus_allowed)) goto fail; - on_rq = p->se.on_rq; - if (on_rq) + /* + * If we're not on a rq, the next wake-up will ensure we're + * placed properly. + */ + if (p->se.on_rq) { deactivate_task(rq_src, p, 0); - - set_task_cpu(p, dest_cpu); - if (on_rq) { + set_task_cpu(p, dest_cpu); activate_task(rq_dest, p, 0); check_preempt_curr(rq_dest, p, 0); } |