perf_counter: uncouple data_head updates from wakeups
Keep data_head up-to-date irrespective of notifications. This fixes
the case where you disable a counter and don't get a notification for
the last few pending events, and it also allows polling usage.
[ Impact: increase precision of perfcounter mmap-ed fields ]
Suggested-by: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090505155436.925084300@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 a356fa6..17b6310 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -362,9 +362,11 @@
atomic_t head; /* write position */
atomic_t events; /* event limit */
- atomic_t wakeup_head; /* completed head */
+ atomic_t done_head; /* completed head */
atomic_t lock; /* concurrent writes */
+ atomic_t wakeup; /* needs a wakeup */
+
struct perf_counter_mmap_page *user_page;
void *data_pages[0];
};