[tip:perf/core] events: Move lockless timer calculation into helper function

tip-bot for Eric B Munson
2011-07-01T15:20:21Z

Commit-ID: c4794295917ebeda8013b6cb9c8d71ab4f74a1fa
Gitweb: http://git.kernel.org/tip/c4794295917ebeda8013b6cb9c8d71ab4f74a1fa
Author: Eric B Munson <emunson@mgebm.net>
AuthorDate: Thu, 23 Jun 2011 16:34:38 -0400
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Fri, 1 Jul 2011 11:06:33 +0200

events: Move lockless timer calculation into helper function

Take the timer calculation from perf_output_read and move it to a helper
function for any place that needs timer values but cannot take the ctx->lock.

Signed-off-by: Eric B Munson <emunson@mgebm.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1308861279-15216-2-git-send-email-emunson@mgebm.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/events/core.c | 22 +++++++++++++++-------
1 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2293e0b..c851d70 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3351,6 +3351,18 @@ static int perf_event_index(struct perf_event *event)
return event->hw.idx + 1 - PERF_EVENT_INDEX_OFFSET;
}

+static void calc_timer_values(struct perf_event *event,
+ u64 *running,
+ u64 *enabled)
+{
+ u64 now, ctx_time;
+
+ now = perf_clock();
+ ctx_time = event->shadow_ctx_time + now;
+ *enabled = ctx_time - event->tstamp_enabled;
+ *running = ctx_time - event->tstamp_running;
+}
+
/*
* Callers need to ensure there can be no nesting of this function, otherwise
* the seqlock logic goes bad. We can not serialize this because the arch
@@ -3816,7 +3828,7 @@ static void perf_output_read_group(struct perf_output_handle *handle,
static void perf_output_read(struct perf_output_handle *handle,
struct perf_event *event)
{
- u64 enabled = 0, running = 0, now, ctx_time;
+ u64 enabled = 0, running = 0;
u64 read_format = event->attr.read_format;

/*
@@ -3828,12 +3840,8 @@ static void perf_output_read(struct perf_output_handle *handle,
* because of locking issue as we are called in
* NMI context
*/
- if (read_format & PERF_FORMAT_TOTAL_TIMES) {
- now = perf_clock();
- ctx_time = event->shadow_ctx_time + now;
- enabled = ctx_time - event->tstamp_enabled;
- running = ctx_time - event->tstamp_running;
- }
+ if (read_format & PERF_FORMAT_TOTAL_TIMES)
+ calc_timer_values(event, &enabled, &running);

if (event->attr.read_format & PERF_FORMAT_GROUP)
perf_output_read_group(handle, event, enabled, running);