* [2.6.16-rc6 patch] smp fix for recalc_task_prio()
@ 2006-03-18 4:37 Mike Galbraith
2006-03-18 4:41 ` Mike Galbraith
0 siblings, 1 reply; 2+ messages in thread
From: Mike Galbraith @ 2006-03-18 4:37 UTC (permalink / raw)
To: lkml; +Cc: Ingo Molnar
Greetings,
The patchlet below fixes an smp buglet where a task goes to sleep on one
cpu and wakes up on another, causing recalc_task_prio() to be called
with now < p->timestamp.
If this isn't 2.6.16 material, and I can respin against mm.
-Mike
--- linux-2.6.16-rc6/kernel/sched.c.org 2006-03-17 14:48:35.000000000 +0100
+++ linux-2.6.16-rc6/kernel/sched.c 2006-03-18 05:22:21.000000000 +0100
@@ -685,6 +685,16 @@
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
+ /*
+ * On SMP systems, a task can go to sleep on one CPU and
+ * wake up on another. When this happens, the timestamp
+ * is rounded to the nearest tick, which can lead to now
+ * being less than p->timestamp for short sleeps. Ignore
+ * these, they're insignificant.
+ */
+ if (unlikely(now < p->timestamp))
+ __sleep_time = 0ULL;
+
if (unlikely(p->policy == SCHED_BATCH))
sleep_time = 0;
else {
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [2.6.16-rc6 patch] smp fix for recalc_task_prio()
2006-03-18 4:37 [2.6.16-rc6 patch] smp fix for recalc_task_prio() Mike Galbraith
@ 2006-03-18 4:41 ` Mike Galbraith
0 siblings, 0 replies; 2+ messages in thread
From: Mike Galbraith @ 2006-03-18 4:41 UTC (permalink / raw)
To: lkml; +Cc: Ingo Molnar
On Sat, 2006-03-18 at 05:37 +0100, Mike Galbraith wrote:
> Greetings,
>
> The patchlet below fixes an smp buglet where a task goes to sleep on one
> cpu and wakes up on another, causing recalc_task_prio() to be called
> with now < p->timestamp.
>
> If this isn't 2.6.16 material, and I can respin against mm.
Sigh. Forgot sob line.
-Mike
Signed-off-by: Mike Galbraith <efault@gmx.de>
--- linux-2.6.16-rc6/kernel/sched.c.org 2006-03-17 14:48:35.000000000 +0100
+++ linux-2.6.16-rc6/kernel/sched.c 2006-03-18 05:22:21.000000000 +0100
@@ -685,6 +685,16 @@
unsigned long long __sleep_time = now - p->timestamp;
unsigned long sleep_time;
+ /*
+ * On SMP systems, a task can go to sleep on one CPU and
+ * wake up on another. When this happens, the timestamp
+ * is rounded to the nearest tick, which can lead to now
+ * being less than p->timestamp for short sleeps. Ignore
+ * these, they're insignificant.
+ */
+ if (unlikely(now < p->timestamp))
+ __sleep_time = 0ULL;
+
if (unlikely(p->policy == SCHED_BATCH))
sleep_time = 0;
else {
^ permalink raw reply [flat|nested] 2+ messages in thread
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