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ANDROID: uid_cputime: Avoids double accounting of process stime, utime and cpu_power in task exit.

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This avoids the race where a particular process is terminating and we
read the show_uid_stats. At this time since the task_struct still exists
and we will account for the terminating process as one of the active
task, where as the stats would have been added in the task exit
callback.

Bug: 22064385
Change-Id: Id2ae04b33fcd230eda9683a41b6019d4dd8f5d85
Signed-off-by: Jin Qian <jinqian@google.com>
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>
This commit is contained in:
Ruchi Kandoi
2015-06-26 14:19:21 -07:00
committed by Dmitry Shmidt
parent bf7cb02771
commit 40b78cc953
1 changed files with 6 additions and 0 deletions
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6
drivers/misc/uid_cputime.c
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@@ -100,6 +100,11 @@ static int uid_stat_show(struct seq_file *m, void *v)
task_uid(task)));
return -ENOMEM;
}
/* if this task is exiting, we have already accounted for the
* time and power.
*/
if (task->cpu_power == ULLONG_MAX)
continue;
task_cputime_adjusted(task, &utime, &stime);
uid_entry->active_utime += utime;
uid_entry->active_stime += stime;
@@ -211,6 +216,7 @@ static int process_notifier(struct notifier_block *self,
uid_entry->utime += utime;
uid_entry->stime += stime;
uid_entry->power += task->cpu_power;
task->cpu_power = ULLONG_MAX;
exit:
mutex_unlock(&uid_lock);