sched: migrate_enable: Use stop_one_cpu_nowait()
migrate_enable() can be called with current->state != TASK_RUNNING. Avoid clobbering the existing state by using stop_one_cpu_nowait(). Since we're stopping the current cpu, we know that we won't get past __schedule() until migration_cpu_stop() has run (at least up to the point of migrating us to another cpu). Signed-off-by: Scott Wood <swood@redhat.com> [bigeasy: spin until the request has been processed] Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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@ -26,6 +26,8 @@ struct cpu_stop_work {
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cpu_stop_fn_t fn;
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void *arg;
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struct cpu_stop_done *done;
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/* Did not run due to disabled stopper; for nowait debug checks */
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bool disabled;
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};
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int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
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@ -1631,6 +1631,7 @@ static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf,
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struct migration_arg {
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struct task_struct *task;
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int dest_cpu;
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bool done;
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};
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/*
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@ -1666,6 +1667,11 @@ static int migration_cpu_stop(void *data)
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struct task_struct *p = arg->task;
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struct rq *rq = this_rq();
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struct rq_flags rf;
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int dest_cpu = arg->dest_cpu;
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/* We don't look at arg after this point. */
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smp_mb();
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arg->done = true;
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/*
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* The original target CPU might have gone down and we might
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@ -1688,9 +1694,9 @@ static int migration_cpu_stop(void *data)
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*/
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if (task_rq(p) == rq) {
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if (task_on_rq_queued(p))
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rq = __migrate_task(rq, &rf, p, arg->dest_cpu);
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rq = __migrate_task(rq, &rf, p, dest_cpu);
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else
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p->wake_cpu = arg->dest_cpu;
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p->wake_cpu = dest_cpu;
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}
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rq_unlock(rq, &rf);
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raw_spin_unlock(&p->pi_lock);
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@ -8272,7 +8278,8 @@ void migrate_enable(void)
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WARN_ON(smp_processor_id() != cpu);
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if (!is_cpu_allowed(p, cpu)) {
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struct migration_arg arg = { p };
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struct migration_arg arg = { .task = p };
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struct cpu_stop_work work;
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struct rq_flags rf;
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rq = task_rq_lock(p, &rf);
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@ -8280,13 +8287,13 @@ void migrate_enable(void)
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arg.dest_cpu = select_fallback_rq(cpu, p);
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task_rq_unlock(rq, p, &rf);
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preempt_enable();
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sleeping_lock_inc();
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stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg);
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sleeping_lock_dec();
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return;
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stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop,
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&arg, &work);
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__schedule(true);
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if (!work.disabled) {
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while (!arg.done)
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cpu_relax();
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}
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}
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out:
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@ -86,8 +86,11 @@ static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
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enabled = stopper->enabled;
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if (enabled)
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__cpu_stop_queue_work(stopper, work, &wakeq);
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else if (work->done)
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cpu_stop_signal_done(work->done);
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else {
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work->disabled = true;
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if (work->done)
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cpu_stop_signal_done(work->done);
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}
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raw_spin_unlock_irqrestore(&stopper->lock, flags);
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wake_up_q(&wakeq);
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