uid_cputime: Avoids double accounting of process stime, utime and cpu…

…_power in 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.

When the task is terminated, the cpu_power for that particular task is
added to the terminated tasks. It is possible that before the task releases all
the resources, cpu reschedules the task or a timer interrupt is fired. At this
point we will try to add the additional time to the process, which will cause
the accounting to be skewed. This avoids that race condition.

Bug: 22064385
Change-Id: Id2ae04b33fcd230eda9683a41b6019d4dd8f5d85
Signed-off-by: Jin Qian <jinqian@google.com>
Signed-off-by: Ruchi Kandoi <kandoiruchi@google.com>
Git-commit: 344377047daa5832ef798af697adee388e367d57
Git-repo: https://android.googlesource.com/kernel/msm/
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>
Signed-off-by: Srinivasarao P <spathi@codeaurora.org>
Change-Id: I405733725d535b0a864088516bf52fa3638ee6aa

Used commit: https://github.com/omnirom/android_kernel_lge_msm8992/commit/e36bbc4edde59683e980c816fb4a432fbbe594bb

diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c
index 529fae6a6df7fea4c97da49d67531412db8e2fca..92067b3d265149fe6540044cdac68ac05ccf164b 100644 (file)
--- a/drivers/cpufreq/cpufreq_stats.c
+++ b/drivers/cpufreq/cpufreq_stats.c
@@ -152,7 +152,8 @@ void acct_update_power(struct task_struct *task, cputime_t cputime) {
                return;
 
        curr = powerstats->curr[stats->last_index];
-       task->cpu_power += curr * cputime_to_usecs(cputime);
+       if (task->cpu_power != ULLONG_MAX)
+               task->cpu_power += curr * cputime_to_usecs(cputime);
 }
 EXPORT_SYMBOL_GPL(acct_update_power);