perf_counter: fix perf_poll()
Impact: fix kerneltop 100% CPU usage
Only return a poll event when there's actually been one, poll_wait()
doesn't actually wait for the waitq you pass it, it only enqueues
you on it.
Only once all FDs have been iterated and none of thm returned a
poll-event will it schedule().
Also make it return POLL_HUP when there's not mmap() area to read from.
Further, fix a silly bug in the write code.
Reported-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arjan van de Ven <arjan@infradead.org>
Orig-LKML-Reference: <1237897096.24918.181.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 2b5e66d..48212c1 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -246,6 +246,7 @@
struct perf_mmap_data {
struct rcu_head rcu_head;
int nr_pages;
+ atomic_t wakeup;
atomic_t head;
struct perf_counter_mmap_page *user_page;
void *data_pages[0];