From: Nick Piggin <nickpiggin@yahoo.com.au>
Some fixes for unsynchronised TSCs. A task's timestamp may have been set by
another CPU. Although we try to adjust this correctly with the
timestamp_last_tick field, there is no guarantee this will be exactly right.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/kernel/sched.c | 7 ++++++-
1 files changed, 6 insertions(+), 1 deletion(-)
diff -puN kernel/sched.c~sched-timestamp-fixes kernel/sched.c
--- 25/kernel/sched.c~sched-timestamp-fixes 2005-02-24 19:54:44.000000000 -0800
+++ 25-akpm/kernel/sched.c 2005-02-24 19:54:44.000000000 -0800
@@ -650,6 +650,7 @@ static inline void __activate_idle_task(
static void recalc_task_prio(task_t *p, unsigned long long now)
{
+ /* Caller must always ensure 'now >= p->timestamp' */
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
@@ -2663,8 +2664,10 @@ need_resched_nonpreemptible:
schedstat_inc(rq, sched_cnt);
now = sched_clock();
- if (likely(now - prev->timestamp < NS_MAX_SLEEP_AVG))
+ if (likely((long long)now - prev->timestamp < NS_MAX_SLEEP_AVG))
run_time = now - prev->timestamp;
+ if (unlikely((long long)now - prev->timestamp < 0))
+ run_time = 0;
else
run_time = NS_MAX_SLEEP_AVG;
@@ -2742,6 +2745,8 @@ go_idle:
if (!rt_task(next) && next->activated > 0) {
unsigned long long delta = now - next->timestamp;
+ if (unlikely((long long)now - next->timestamp < 0))
+ delta = 0;
if (next->activated == 1)
delta = delta * (ON_RUNQUEUE_WEIGHT * 128 / 100) / 128;
_