From 874bae78eb0b7aa2ac939636ba0031962633f841 Mon Sep 17 00:00:00 2001 From: Ruchi Kandoi Date: Fri, 26 Jun 2015 14:19:21 -0700 Subject: uid_cputime: Fixes double accounting race condition on task exit. 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 Signed-off-by: Ruchi Kandoi --- drivers/misc/uid_cputime.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/misc/uid_cputime.c b/drivers/misc/uid_cputime.c index ad32727..73ed8b2 100644 --- a/drivers/misc/uid_cputime.c +++ b/drivers/misc/uid_cputime.c @@ -101,6 +101,10 @@ static int uid_stat_show(struct seq_file *m, void *v) __func__, 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_times(task, &utime, &stime); uid_entry->active_utime += utime; uid_entry->active_stime += stime; @@ -212,6 +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); -- cgit v1.1