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Commit ba74c144 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
Browse files

sched/rt: Document scheduler related skip-resched-check sites 



Create a distinction between scheduler related preempt_enable_no_resched()
calls and the nearly one hundred other places in the kernel that do not
want to reschedule, for one reason or another.

This distinction matters for -rt, where the scheduler and the non-scheduler
preempt models (and checks) are different. For upstream it's purely
documentational.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/n/tip-gs88fvx2mdv5psnzxnv575ke@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent bd2f5536

arch/powerpc/kernel/idle.c

+1 −1
Original line number Diff line number Diff line
@@ -102,7 +102,7 @@ void cpu_idle(void) 
		rcu_idle_exit();

		tick_nohz_idle_exit();

		if (cpu_should_die()) {

			preempt_enable_no_resched();

			sched_preempt_enable_no_resched();

			cpu_die();

		}

		schedule_preempt_disabled();

arch/sparc/kernel/process_64.c

+1 −1
Original line number Diff line number Diff line
@@ -106,7 +106,7 @@ void cpu_idle(void) 


#ifdef CONFIG_HOTPLUG_CPU

		if (cpu_is_offline(cpu)) {

			preempt_enable_no_resched();

			sched_preempt_enable_no_resched();

			cpu_play_dead();

		}

#endif

include/linux/preempt.h

+4 −1
Original line number Diff line number Diff line
@@ -48,12 +48,14 @@ do { \ 
	barrier(); \

} while (0)



#define preempt_enable_no_resched() \

#define sched_preempt_enable_no_resched() \

do { \

	barrier(); \

	dec_preempt_count(); \

} while (0)



#define preempt_enable_no_resched()	sched_preempt_enable_no_resched()



#define preempt_enable() \

do { \

	preempt_enable_no_resched(); \
@@ -92,6 +94,7 @@ do { \ 
#else /* !CONFIG_PREEMPT_COUNT */



#define preempt_disable()		do { } while (0)

#define sched_preempt_enable_no_resched()	do { } while (0)

#define preempt_enable_no_resched()	do { } while (0)

#define preempt_enable()		do { } while (0)

kernel/sched/core.c

+3 −3
Original line number Diff line number Diff line
@@ -3220,7 +3220,7 @@ static void __sched __schedule(void) 


	post_schedule(rq);



	preempt_enable_no_resched();

	sched_preempt_enable_no_resched();

	if (need_resched())

		goto need_resched;

}
@@ -3253,7 +3253,7 @@ EXPORT_SYMBOL(schedule); 
 */

void __sched schedule_preempt_disabled(void)

{

	preempt_enable_no_resched();

	sched_preempt_enable_no_resched();

	schedule();

	preempt_disable();

}
@@ -4486,7 +4486,7 @@ SYSCALL_DEFINE0(sched_yield) 
	__release(rq->lock);

	spin_release(&rq->lock.dep_map, 1, _THIS_IP_);

	do_raw_spin_unlock(&rq->lock);

	preempt_enable_no_resched();

	sched_preempt_enable_no_resched();



	schedule();

kernel/softirq.c

+2 −2
Original line number Diff line number Diff line
@@ -353,7 +353,7 @@ void irq_exit(void) 
		tick_nohz_irq_exit();

#endif

	rcu_irq_exit();

	preempt_enable_no_resched();

	sched_preempt_enable_no_resched();

}



/*
@@ -759,7 +759,7 @@ static int run_ksoftirqd(void * __bind_cpu) 
			if (local_softirq_pending())

				__do_softirq();

			local_irq_enable();

			preempt_enable_no_resched();

			sched_preempt_enable_no_resched();

			cond_resched();

			preempt_disable();

			rcu_note_context_switch((long)__bind_cpu);