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| author | Peter Zijlstra <peterz@infradead.org> | 2009-03-24 13:18:16 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-04-06 09:30:32 +0200 |
| commit | c7138f37f905bb7987b1f9f5a8ee73667db39f25 (patch) | |
| tree | 8d1c2bf404f1179d35e8b35b0166c7bf0b39840e | |
| parent | f66c6b2066b44d4ab8e8ac1ee4cae543738fe2ac (diff) | |
| download | lwn-c7138f37f905bb7987b1f9f5a8ee73667db39f25.tar.gz lwn-c7138f37f905bb7987b1f9f5a8ee73667db39f25.zip | |
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>
| -rw-r--r-- | include/linux/perf_counter.h | 1 | ||||
| -rw-r--r-- | kernel/perf_counter.c | 14 |
2 files changed, 13 insertions, 2 deletions
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 2b5e66d5ebdf..48212c15b7d6 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -246,6 +246,7 @@ struct file; 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]; diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 0dfe91094fd1..affe227d56a0 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -1161,7 +1161,16 @@ perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) static unsigned int perf_poll(struct file *file, poll_table *wait) { struct perf_counter *counter = file->private_data; - unsigned int events = POLLIN; + struct perf_mmap_data *data; + unsigned int events; + + rcu_read_lock(); + data = rcu_dereference(counter->data); + if (data) + events = atomic_xchg(&data->wakeup, 0); + else + events = POLL_HUP; + rcu_read_unlock(); poll_wait(file, &counter->waitq, wait); @@ -1425,7 +1434,7 @@ static int perf_output_write(struct perf_counter *counter, int nmi, do { offset = head = atomic_read(&data->head); - head += sizeof(u64); + head += size; } while (atomic_cmpxchg(&data->head, offset, head) != offset); wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT); @@ -1446,6 +1455,7 @@ static int perf_output_write(struct perf_counter *counter, int nmi, * generate a poll() wakeup for every page boundary crossed */ if (wakeup) { + atomic_xchg(&data->wakeup, POLL_IN); __perf_counter_update_userpage(counter, data); if (nmi) { counter->wakeup_pending = 1; |