timers: split process wide cpu clocks/timers, fix

To decrease the chance of a missed enable, always enable the timer when we sample it, we'll always disable it when we find that there are no active timers in the jiffy tick. This fixes a flood of warnings reported by Mike Galbraith. Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>

timers: split process wide cpu clocks/timers, fix
To decrease the chance of a missed enable, always enable the timer when we sample it, we'll always disable it when we find that there are no active timers in the jiffy tick. This fixes a flood of warnings reported by Mike Galbraith. Reported-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Peter Zijlstra · Ingo Molnar
1 parent ff08f76d73
Showing 2 changed files with 15 additions and 28 deletions Side-by-side Diff
include/linux/sched.h
kernel/posix-cpu-timers.c
@@ -2209,6 +2209,7 @@
 	unsigned long flags;
  
 	spin_lock_irqsave(&cputimer->lock, flags);
+	cputimer->running = 1;
 	*times = cputimer->cputime;
 	spin_unlock_irqrestore(&cputimer->lock, flags);
 }
@@ -488,7 +488,7 @@
 {
 	struct task_cputime cputime;
  
-	thread_group_cputime(tsk, &cputime);
+	thread_group_cputimer(tsk, &cputime);
 	cleanup_timers(tsk->signal->cpu_timers,
 		       cputime.utime, cputime.stime, cputime.sum_exec_runtime);
 }
@@ -507,29 +507,6 @@
 }
  
 /*
- * Enable the process wide cpu timer accounting.
- *
- * serialized using ->sighand->siglock
- */
-static void start_process_timers(struct task_struct *tsk)
-{
-	tsk->signal->cputimer.running = 1;
-	barrier();
-}
-
-/*
- * Release the process wide timer accounting -- timer stops ticking when
- * nobody cares about it.
- *
- * serialized using ->sighand->siglock
- */
-static void stop_process_timers(struct task_struct *tsk)
-{
-	tsk->signal->cputimer.running = 0;
-	barrier();
-}
-
-/*
  * Insert the timer on the appropriate list before any timers that
  * expire later.  This must be called with the tasklist_lock held
  * for reading, and interrupts disabled.
@@ -549,9 +526,6 @@
 	BUG_ON(!irqs_disabled());
 	spin_lock(&p->sighand->siglock);
  
-	if (!CPUCLOCK_PERTHREAD(timer->it_clock))
-		start_process_timers(p);
-
 	listpos = head;
 	if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 		list_for_each_entry(next, head, entry) {
@@ -1021,6 +995,19 @@
 	}
 }
  
+static void stop_process_timers(struct task_struct *tsk)
+{
+	struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
+	unsigned long flags;
+
+	if (!cputimer->running)
+		return;
+
+	spin_lock_irqsave(&cputimer->lock, flags);
+	cputimer->running = 0;
+	spin_unlock_irqrestore(&cputimer->lock, flags);
+}
+
 /*
  * Check for any per-thread CPU timers that have fired and move them
  * off the tsk->*_timers list onto the firing list.  Per-thread timers
@@ -1427,7 +1414,6 @@
 	struct list_head *head;
  
 	BUG_ON(clock_idx == CPUCLOCK_SCHED);
-	start_process_timers(tsk);
 	cpu_timer_sample_group(clock_idx, tsk, &now);
  
 	if (oldval) {
...	...	@@ -2209,6 +2209,7 @@
2209	2209	unsigned long flags;
2210	2210
2211	2211	spin_lock_irqsave(&cputimer->lock, flags);
	2212	+ cputimer->running = 1;
2212	2213	*times = cputimer->cputime;
2213	2214	spin_unlock_irqrestore(&cputimer->lock, flags);
2214	2215	}
...	...	@@ -488,7 +488,7 @@
488	488	{
489	489	struct task_cputime cputime;
490	490
491		- thread_group_cputime(tsk, &cputime);
	491	+ thread_group_cputimer(tsk, &cputime);
492	492	cleanup_timers(tsk->signal->cpu_timers,
493	493	cputime.utime, cputime.stime, cputime.sum_exec_runtime);
494	494	}
...	...	@@ -507,29 +507,6 @@
507	507	}
508	508
509	509	/*
510		- * Enable the process wide cpu timer accounting.
511		- *
512		- * serialized using ->sighand->siglock
513		- */
514		-static void start_process_timers(struct task_struct *tsk)
515		-{
516		- tsk->signal->cputimer.running = 1;
517		- barrier();
518		-}
519		-
520		-/*
521		- * Release the process wide timer accounting -- timer stops ticking when
522		- * nobody cares about it.
523		- *
524		- * serialized using ->sighand->siglock
525		- */
526		-static void stop_process_timers(struct task_struct *tsk)
527		-{
528		- tsk->signal->cputimer.running = 0;
529		- barrier();
530		-}
531		-
532		-/*
533	510	* Insert the timer on the appropriate list before any timers that
534	511	* expire later. This must be called with the tasklist_lock held
535	512	* for reading, and interrupts disabled.
...	...	@@ -549,9 +526,6 @@
549	526	BUG_ON(!irqs_disabled());
550	527	spin_lock(&p->sighand->siglock);
551	528
552		- if (!CPUCLOCK_PERTHREAD(timer->it_clock))
553		- start_process_timers(p);
554		-
555	529	listpos = head;
556	530	if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
557	531	list_for_each_entry(next, head, entry) {
...	...	@@ -1021,6 +995,19 @@
1021	995	}
1022	996	}
1023	997
	998	+static void stop_process_timers(struct task_struct *tsk)
	999	+{
	1000	+ struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
	1001	+ unsigned long flags;
	1002	+
	1003	+ if (!cputimer->running)
	1004	+ return;
	1005	+
	1006	+ spin_lock_irqsave(&cputimer->lock, flags);
	1007	+ cputimer->running = 0;
	1008	+ spin_unlock_irqrestore(&cputimer->lock, flags);
	1009	+}
	1010	+
1024	1011	/*
1025	1012	* Check for any per-thread CPU timers that have fired and move them
1026	1013	* off the tsk->*_timers list onto the firing list. Per-thread timers
...	...	@@ -1427,7 +1414,6 @@
1427	1414	struct list_head *head;
1428	1415
1429	1416	BUG_ON(clock_idx == CPUCLOCK_SCHED);
1430		- start_process_timers(tsk);
1431	1417	cpu_timer_sample_group(clock_idx, tsk, &now);
1432	1418
1433	1419	if (oldval) {