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Commit 3472eaa1 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Ingo Molnar
Browse files

sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock() 



1. read_lock(tasklist_lock) does not need to disable irqs.

2. ->mm != NULL is a common mistake, use PF_KTHREAD.

3. The second ->mm check can be simply removed.

4. task_rq_lock() looks better than raw_spin_lock(&p->pi_lock) +
   __task_rq_lock().

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140921193338.GA28621@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8651c658

kernel/sched/core.c

+6 −10
Original line number Diff line number Diff line
@@ -7220,12 +7220,12 @@ void normalize_rt_tasks(void) 
	unsigned long flags;

	struct rq *rq;



	read_lock_irqsave(&tasklist_lock, flags);

	read_lock(&tasklist_lock);

	for_each_process_thread(g, p) {

		/*

		 * Only normalize user tasks:

		 */

		if (!p->mm)

		if (p->flags & PF_KTHREAD)

			continue;



		p->se.exec_start		= 0;
@@ -7240,20 +7240,16 @@ void normalize_rt_tasks(void) 
			 * Renice negative nice level userspace

			 * tasks back to 0:

			 */

			if (task_nice(p) < 0 && p->mm)

			if (task_nice(p) < 0)

				set_user_nice(p, 0);

			continue;

		}



		raw_spin_lock(&p->pi_lock);

		rq = __task_rq_lock(p);



		rq = task_rq_lock(p, &flags);

		normalize_task(rq, p);



		__task_rq_unlock(rq);

		raw_spin_unlock(&p->pi_lock);

		task_rq_unlock(rq, p, &flags);

	}

	read_unlock_irqrestore(&tasklist_lock, flags);

	read_unlock(&tasklist_lock);

}



#endif /* CONFIG_MAGIC_SYSRQ */