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Subject[2.6.16-rc6 patch] smp fix for recalc_task_prio()
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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 {


-
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