perf_counter: Fix dynamic irq_period logging

We call perf_adjust_freq() from perf_counter_task_tick() which
is is called under the rq->lock causing lock recursion.
However, it's no longer required to be called under the
rq->lock, so remove it from under it.

Also, fix up some related comments.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
LKML-Reference: <20090523163012.476197912@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/perf_counter.h

@@ -260,6 +260,7 @@ enum perf_event_type {
 	/*
 	 * struct {
 	 * 	struct perf_event_header	header;
+	 * 	u64				time;
 	 * 	u64				irq_period;
 	 * };
 	 */

kernel/perf_counter.c

@@ -2559,7 +2559,8 @@ void perf_counter_munmap(unsigned long addr, unsigned long len,
 }
 
 /*
- *
+ * Log irq_period changes so that analyzing tools can re-normalize the
+ * event flow.
  */
 
 static void perf_log_period(struct perf_counter *counter, u64 period)

kernel/sched.c

@@ -4875,9 +4875,10 @@ void scheduler_tick(void)
 	update_rq_clock(rq);
 	update_cpu_load(rq);
 	curr->sched_class->task_tick(rq, curr, 0);
-	perf_counter_task_tick(curr, cpu);
 	spin_unlock(&rq->lock);
 
+	perf_counter_task_tick(curr, cpu);
+
 #ifdef CONFIG_SMP
 	rq->idle_at_tick = idle_cpu(cpu);
 	trigger_load_balance(rq, cpu);