perf_counter: Change pctrl() behaviour

Instead of en/dis-abling all counters acting on a particular
task, en/dis- able all counters we created.

[ v2: fix crash on first counter enable ]

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: <20090523163012.916937244@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 4ab8050..4159ee5 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -469,6 +469,9 @@
 	int				oncpu;
 	int				cpu;
 
+	struct list_head		owner_entry;
+	struct task_struct		*owner;
+
 	/* mmap bits */
 	struct mutex			mmap_mutex;
 	atomic_t			mmap_count;