perf_counter: SIGIO support

Provide support for fcntl() I/O availability signals.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090406094517.579788800@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 f9d5cf0..8d5d11b 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -238,6 +238,7 @@
 #include <linux/rcupdate.h>
 #include <linux/spinlock.h>
 #include <linux/hrtimer.h>
+#include <linux/fs.h>
 #include <asm/atomic.h>
 
 struct task_struct;
@@ -398,6 +399,7 @@
 
 	/* poll related */
 	wait_queue_head_t		waitq;
+	struct fasync_struct		*fasync;
 	/* optional: for NMIs */
 	struct perf_wakeup_entry	wakeup;