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authorBalbir Singh <balbir@linux.vnet.ibm.com>2008-09-05 18:12:23 +0200
committerIngo Molnar <mingo@elte.hu>2008-09-05 18:14:35 +0200
commit49048622eae698e5c4ae61f7e71200f265ccc529 (patch)
treee568595fe5329e1293eafc3a3cc833dfe89ffbf2
parent56c7426b3951e4f35a71d695f1c982989399d6fd (diff)
sched: fix process time monotonicity
Spencer reported a problem where utime and stime were going negative despite the fixes in commit b27f03d4bdc145a09fb7b0c0e004b29f1ee555fa. The suspected reason for the problem is that signal_struct maintains it's own utime and stime (of exited tasks), these are not updated using the new task_utime() routine, hence sig->utime can go backwards and cause the same problem to occur (sig->utime, adds tsk->utime and not task_utime()). This patch fixes the problem TODO: using max(task->prev_utime, derived utime) works for now, but a more generic solution is to implement cputime_max() and use the cputime_gt() function for comparison. Reported-by: spencer@bluehost.com Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--fs/proc/array.c59
-rw-r--r--include/linux/sched.h4
-rw-r--r--kernel/exit.c6
-rw-r--r--kernel/sched.c59
4 files changed, 66 insertions, 62 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c
index 0d6eb33597c..71c9be59c9c 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -337,65 +337,6 @@ int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
return 0;
}
-/*
- * Use precise platform statistics if available:
- */
-#ifdef CONFIG_VIRT_CPU_ACCOUNTING
-static cputime_t task_utime(struct task_struct *p)
-{
- return p->utime;
-}
-
-static cputime_t task_stime(struct task_struct *p)
-{
- return p->stime;
-}
-#else
-static 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;
-}
-
-static 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
-
-static cputime_t task_gtime(struct task_struct *p)
-{
- return p->gtime;
-}
-
static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task, int whole)
{
diff --git a/include/linux/sched.h b/include/linux/sched.h
index cfb0d87b99f..3d9120c5ad1 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1475,6 +1475,10 @@ static inline void put_task_struct(struct task_struct *t)
__put_task_struct(t);
}
+extern cputime_t task_utime(struct task_struct *p);
+extern cputime_t task_stime(struct task_struct *p);
+extern cputime_t task_gtime(struct task_struct *p);
+
/*
* Per process flags
*/
diff --git a/kernel/exit.c b/kernel/exit.c
index 25ed2ad986d..16395644a98 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -112,9 +112,9 @@ static void __exit_signal(struct task_struct *tsk)
* We won't ever get here for the group leader, since it
* will have been the last reference on the signal_struct.
*/
- sig->utime = cputime_add(sig->utime, tsk->utime);
- sig->stime = cputime_add(sig->stime, tsk->stime);
- sig->gtime = cputime_add(sig->gtime, tsk->gtime);
+ sig->utime = cputime_add(sig->utime, task_utime(tsk));
+ sig->stime = cputime_add(sig->stime, task_stime(tsk));
+ sig->gtime = cputime_add(sig->gtime, task_gtime(tsk));
sig->min_flt += tsk->min_flt;
sig->maj_flt += tsk->maj_flt;
sig->nvcsw += tsk->nvcsw;
diff --git a/kernel/sched.c b/kernel/sched.c
index 9a1ddb84e26..1a5f73c1fcd 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -4179,6 +4179,65 @@ void account_steal_time(struct task_struct *p, cputime_t steal)
}
/*
+ * 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.
*