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Commit 01028747 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Create more preempt_count accessors 



We need a few special preempt_count accessors:
 - task_preempt_count() for when we're interested in the preemption
   count of another (non-running) task.
 - init_task_preempt_count() for properly initializing the preemption
   count.
 - init_idle_preempt_count() a special case of the above for the idle
   threads.

With these no generic code ever touches thread_info::preempt_count
anymore and architectures could choose to remove it.

Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent a7878709

include/asm-generic/preempt.h

+14 −0
Original line number Diff line number Diff line
@@ -27,6 +27,20 @@ static __always_inline void preempt_count_set(int pc) 
	*preempt_count_ptr() = pc;

}



/*

 * must be macros to avoid header recursion hell

 */

#define task_preempt_count(p) \

	(task_thread_info(p)->preempt_count & ~PREEMPT_NEED_RESCHED)



#define init_task_preempt_count(p) do { \

	task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \

} while (0)



#define init_idle_preempt_count(p, cpu) do { \

	task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \

} while (0)



/*

 * We fold the NEED_RESCHED bit into the preempt count such that

 * preempt_enable() can decrement and test for needing to reschedule with a

include/trace/events/sched.h

+1 −1
Original line number Diff line number Diff line
@@ -100,7 +100,7 @@ static inline long __trace_sched_switch_state(struct task_struct *p) 
	/*

	 * For all intents and purposes a preempted task is a running task.

	 */

	if (task_thread_info(p)->preempt_count & PREEMPT_ACTIVE)

	if (task_preempt_count(p) & PREEMPT_ACTIVE)

		state = TASK_RUNNING | TASK_STATE_MAX;

#endif

kernel/sched/core.c

+3 −4
Original line number Diff line number Diff line
@@ -983,7 +983,7 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) 
	 * ttwu() will sort out the placement.

	 */

	WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&

			!(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));

			!(task_preempt_count(p) & PREEMPT_ACTIVE));



#ifdef CONFIG_LOCKDEP

	/*
@@ -1723,8 +1723,7 @@ void sched_fork(struct task_struct *p) 
	p->on_cpu = 0;

#endif

#ifdef CONFIG_PREEMPT_COUNT

	/* Want to start with kernel preemption disabled. */

	task_thread_info(p)->preempt_count = PREEMPT_DISABLED;

	init_task_preempt_count(p);

#endif

#ifdef CONFIG_SMP

	plist_node_init(&p->pushable_tasks, MAX_PRIO);
@@ -4217,7 +4216,7 @@ void init_idle(struct task_struct *idle, int cpu) 
	raw_spin_unlock_irqrestore(&rq->lock, flags);



	/* Set the preempt count _outside_ the spinlocks! */

	task_thread_info(idle)->preempt_count = PREEMPT_ENABLED;

	init_idle_preempt_count(idle, cpu);



	/*

	 * The idle tasks have their own, simple scheduling class: