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>

1 files changed, 15 insertions, 7 deletions

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2293e0b084a9..c851d707821f 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);