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Commit 02f72694 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched, trace: Fix sched_switch() prev_state argument 



For CONFIG_PREEMPT=y kernels the sched_switch(.prev_state) argument isn't
useful because we can get preempted with current->state != TASK_RUNNING
without actually getting removed from the runqueue.

Cure this by treating all preempted tasks as runnable from the tracer's
point of view.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cautiously-acked-by: default avatarSteven Rostedt <rostedt@goodmis.org>
LKML-Reference: <1275322715.27810.23323.camel@twins>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e51fd5e2

include/trace/events/sched.h

+18 −1
Original line number Diff line number Diff line
@@ -115,6 +115,23 @@ DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new, 
	     TP_PROTO(struct task_struct *p, int success),

	     TP_ARGS(p, success));



#ifdef CREATE_TRACE_POINTS

static inline long __trace_sched_switch_state(struct task_struct *p)

{

	long state = p->state;



#ifdef CONFIG_PREEMPT

	/*

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

	 */

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

		state = TASK_RUNNING;

#endif



	return state;

}

#endif



/*

 * Tracepoint for task switches, performed by the scheduler:

 */
@@ -139,7 +156,7 @@ TRACE_EVENT(sched_switch, 
		memcpy(__entry->next_comm, next->comm, TASK_COMM_LEN);

		__entry->prev_pid	= prev->pid;

		__entry->prev_prio	= prev->prio;

		__entry->prev_state	= prev->state;

		__entry->prev_state	= __trace_sched_switch_state(prev);

		memcpy(__entry->prev_comm, prev->comm, TASK_COMM_LEN);

		__entry->next_pid	= next->pid;

		__entry->next_prio	= next->prio;