sched: fix /proc/<PID>/stat stime/utime monotonicity, part 2

Extend Peter's patch to fix accounting issues, by keeping stime
monotonic too.

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Tested-by: Frans Pop <elendil@planet.nl>

3 files changed, 4 insertions, 2 deletions

diff --git a/fs/proc/array.c b/fs/proc/array.c
index d80baaabf835..eba339ecba27 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -374,7 +374,8 @@ static cputime_t task_stime(struct task_struct *p)
         stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
                         cputime_to_clock_t(task_utime(p));
 
-        return clock_t_to_cputime(stime);
+        p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
+        return p->prev_stime;
 }
 #endif
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index b0b1fe6e0b17..155d7438f7ad 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1009,7 +1009,7 @@ struct task_struct {
         unsigned int rt_priority;
         cputime_t utime, stime, utimescaled, stimescaled;
         cputime_t gtime;
-        cputime_t prev_utime;
+        cputime_t prev_utime, prev_stime;
         unsigned long nvcsw, nivcsw; /* context switch counts */
         struct timespec start_time;             /* monotonic time */
         struct timespec real_start_time;        /* boot based time */
diff --git a/kernel/fork.c b/kernel/fork.c
index a65bfc47177c..28a740151988 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1057,6 +1057,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         p->utimescaled = cputime_zero;
         p->stimescaled = cputime_zero;
         p->prev_utime = cputime_zero;
+        p->prev_stime = cputime_zero;
 
 #ifdef CONFIG_TASK_XACCT
         p->rchar = 0;           /* I/O counter: bytes read */