commit 3077a3d4222d821e90c91a6b2f8bca8f0149de11
author Pavlin Radoslavov <pavlin@google.com> Mon Jan 08 11:37:05 2018 -0800
committer Ryan Longair <rlongair@google.com> Wed Jan 17 16:51:04 2018 -0800
tree 1d7fd5bf63f0a761c753cce9191c45e80ead3de8
parent 6ba7064c63270f239fc5677e2e76d19f3a435e33

Removed alarm callback execution statistics

Updating the alarm state after the callback returns can be problematic
in case the callback itself deleted the alarm.

Bug: 67110137
Test: Manual
Change-Id: Id4de06eebedb792cadd63d09efb68672e9bddc69
Merged-In: Id4de06eebedb792cadd63d09efb68672e9bddc69
(cherry picked from commit 04574e1cde3b0d46b59b4b6ebab935ac60af9f97)
(cherry picked from commit b9ebb4ab26e27d0701d43faee775c1b1975d0191)

osi/src/alarm.c

diff --git a/osi/src/alarm.c b/osi/src/alarm.c
index 69ded69..ab4ed12 100644
--- a/osi/src/alarm.c
+++ b/osi/src/alarm.c
@@ -64,7 +64,6 @@
   size_t rescheduled_count;
   size_t total_updates;
   period_ms_t last_update_ms;
-  stat_t callback_execution;
   stat_t overdue_scheduling;
   stat_t premature_scheduling;
 } alarm_stats_t;
@@ -134,10 +133,8 @@
 static void timer_callback(void *data);
 static void callback_dispatch(void *context);
 static bool timer_create_internal(const clockid_t clock_id, timer_t *timer);
-static void update_scheduling_stats(alarm_stats_t *stats,
-                                    period_ms_t now_ms,
-                                    period_ms_t deadline_ms,
-                                    period_ms_t execution_delta_ms);
+static void update_scheduling_stats(alarm_stats_t *stats, period_ms_t now_ms,
+                                    period_ms_t deadline_ms);
 
 static void update_stat(stat_t *stat, period_ms_t delta)
 {
@@ -614,14 +611,12 @@
   pthread_mutex_lock(&alarm->callback_lock);
   pthread_mutex_unlock(&monitor);
 
-  period_ms_t t0 = now();
-  callback(data);
-  period_ms_t t1 = now();
-
   // Update the statistics
-  assert(t1 >= t0);
-  period_ms_t delta = t1 - t0;
-  update_scheduling_stats(&alarm->stats, t0, deadline, delta);
+  update_scheduling_stats(&alarm->stats, now(), deadline);
+
+  // NOTE: Do NOT access "alarm" after the callback, as a safety precaution
+  // in case the callback itself deleted the alarm.
+  callback(data);
 
   pthread_mutex_unlock(&alarm->callback_lock);
 }
@@ -693,16 +688,11 @@
   return true;
 }
 
-static void update_scheduling_stats(alarm_stats_t *stats,
-                                    period_ms_t now_ms,
-                                    period_ms_t deadline_ms,
-                                    period_ms_t execution_delta_ms)
-{
+static void update_scheduling_stats(alarm_stats_t *stats, period_ms_t now_ms,
+                                    period_ms_t deadline_ms) {
   stats->total_updates++;
   stats->last_update_ms = now_ms;
 
-  update_stat(&stats->callback_execution, execution_delta_ms);
-
   if (deadline_ms < now_ms) {
     // Overdue scheduling
     period_ms_t delta_ms = now_ms - deadline_ms;
@@ -755,7 +745,7 @@
     dprintf(fd, "%-51s: %zu / %zu / %zu / %zu\n",
             "    Action counts (sched/resched/exec/cancel)",
             stats->scheduled_count, stats->rescheduled_count,
-            stats->callback_execution.count, stats->canceled_count);
+            stats->total_updates, stats->canceled_count);
 
     dprintf(fd, "%-51s: %zu / %zu\n",
             "    Deviation counts (overdue/premature)",
@@ -768,9 +758,6 @@
             (unsigned long long) alarm->period,
             (long long)(alarm->deadline - just_now));
 
-    dump_stat(fd, &stats->callback_execution,
-              "    Callback execution time in ms (total/max/avg)");
-
     dump_stat(fd, &stats->overdue_scheduling,
               "    Overdue scheduling time in ms (total/max/avg)");