sched: fix process time monotonicity

[linux-2.6-omap-h63xx.git] / kernel / sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index 9a1ddb84e26d56e7d6b283daab1edbad20ae2042..1a5f73c1fcdcd12983c6a2eed9ef66e630dca837 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4178,6 +4178,65 @@ void account_steal_time(struct task_struct *p, cputime_t steal)
                cpustat->steal = cputime64_add(cpustat->steal, tmp);
 }
 
+/*
+ * Use precise platform statistics if available:
+ */
+#ifdef CONFIG_VIRT_CPU_ACCOUNTING
+cputime_t task_utime(struct task_struct *p)
+{
+       return p->utime;
+}
+
+cputime_t task_stime(struct task_struct *p)
+{
+       return p->stime;
+}
+#else
+cputime_t task_utime(struct task_struct *p)
+{
+       clock_t utime = cputime_to_clock_t(p->utime),
+               total = utime + cputime_to_clock_t(p->stime);
+       u64 temp;
+
+       /*
+        * Use CFS's precise accounting:
+        */
+       temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime);
+
+       if (total) {
+               temp *= utime;
+               do_div(temp, total);
+       }
+       utime = (clock_t)temp;
+
+       p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime));
+       return p->prev_utime;
+}
+
+cputime_t task_stime(struct task_struct *p)
+{
+       clock_t stime;
+
+       /*
+        * Use CFS's precise accounting. (we subtract utime from
+        * the total, to make sure the total observed by userspace
+        * grows monotonically - apps rely on that):
+        */
+       stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
+                       cputime_to_clock_t(task_utime(p));
+
+       if (stime >= 0)
+               p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
+
+       return p->prev_stime;
+}
+#endif
+
+inline cputime_t task_gtime(struct task_struct *p)
+{
+       return p->gtime;
+}
+
 /*
  * This function gets called by the timer code, with HZ frequency.
  * We call it with interrupts disabled.