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>
diff --git a/kernel/sched.c b/kernel/sched.c
index 4c0d58b..ad079f0 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4875,9 +4875,10 @@
 	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);