sched: normalize_rt_tasks(): Don't use _irqsave for tasklist_lock, use task_rq_lock() (3472eaa1) · Commits · 戴 / test

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:

Oleg Nesterov <oleg@redhat.com> Signed-off-by:

Peter 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:

Ingo Molnar <mingo@kernel.org>

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 */

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