perf_counter: Simplify context cleanup

Use perf_counter_remove_from_context() to remove counters from
the context.

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: <20090523163012.796275849@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/perf_counter.c

@@ -3416,10 +3416,7 @@ __perf_counter_exit_task(struct task_struct *child,
 	struct perf_counter *parent_counter;
 
 	update_counter_times(child_counter);
-
-	spin_lock_irq(&child_ctx->lock);
-	list_del_counter(child_counter, child_ctx);
-	spin_unlock_irq(&child_ctx->lock);
+	perf_counter_remove_from_context(child_counter);
 
 	parent_counter = child_counter->parent;
 	/*