Commit-ID: 47a6aae483f6b98509a4565ad2d8916de77ee078 Gitweb: http://git.kernel.org/tip/47a6aae483f6b98509a4565ad2d8916de77ee078 Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx> AuthorDate: Tue, 24 Mar 2009 13:18:16 +0100 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Tue, 24 Mar 2009 13:28:56 +0100 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@xxxxxx> Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Arjan van de Ven <arjan@xxxxxxxxxxxxx> LKML-Reference: <1237897096.24918.181.camel@twins> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- include/linux/perf_counter.h | 1 + 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 2b5e66d..48212c1 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 0dfe910..affe227 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; -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html