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Commit 4da94d49 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

timers: fix TIMER_ABSTIME for process wide cpu timers 



The POSIX timer interface allows for absolute time expiry values through the
TIMER_ABSTIME flag, therefore we have to synchronize the timer to the clock
every time we start it.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 3fccfd67

include/linux/sched.h

+1 −12
Original line number Diff line number Diff line
@@ -2201,18 +2201,7 @@ static inline int spin_needbreak(spinlock_t *lock) 
 * Thread group CPU time accounting.

 */

void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times);



static inline

void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)

{

	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;

	unsigned long flags;



	spin_lock_irqsave(&cputimer->lock, flags);

	cputimer->running = 1;

	*times = cputimer->cputime;

	spin_unlock_irqrestore(&cputimer->lock, flags);

}

void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times);



static inline void thread_group_cputime_init(struct signal_struct *sig)

{

kernel/posix-cpu-timers.c

+34 −0
Original line number Diff line number Diff line
@@ -261,6 +261,40 @@ out: 
	rcu_read_unlock();

}



static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)

{

	if (cputime_gt(b->utime, a->utime))

		a->utime = b->utime;



	if (cputime_gt(b->stime, a->stime))

		a->stime = b->stime;



	if (b->sum_exec_runtime > a->sum_exec_runtime)

		a->sum_exec_runtime = b->sum_exec_runtime;

}



void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)

{

	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;

	struct task_cputime sum;

	unsigned long flags;



	spin_lock_irqsave(&cputimer->lock, flags);

	if (!cputimer->running) {

		cputimer->running = 1;

		/*

		 * The POSIX timer interface allows for absolute time expiry

		 * values through the TIMER_ABSTIME flag, therefore we have

		 * to synchronize the timer to the clock every time we start

		 * it.

		 */

		thread_group_cputime(tsk, &sum);

		update_gt_cputime(&cputimer->cputime, &sum);

	}

	*times = cputimer->cputime;

	spin_unlock_irqrestore(&cputimer->lock, flags);

}



/*

 * Sample a process (thread group) clock for the given group_leader task.

 * Must be called with tasklist_lock held for reading.