2.6.23-stable review patch. If anyone has any objections, please let us
know.
------------------
From: Chuck Ebbert <[email protected]>
No patch in mainline as this logic has been removed from 2.6.24 so it is
not necessary.
https://bugzilla.redhat.com/show_bug.cgi?id=340161
The problem code has been removed in 2.6.24. The below patch disables
SCHED_FEAT_PRECISE_CPU_LOAD which causes the offending code to be skipped
but does not prevent the user from enabling it.
The divide-by-zero is here in kernel/sched.c:
static void update_cpu_load(struct rq *this_rq)
{
u64 fair_delta64, exec_delta64, idle_delta64, sample_interval64, tmp64;
unsigned long total_load = this_rq->ls.load.weight;
unsigned long this_load = total_load;
struct load_stat *ls = &this_rq->ls;
int i, scale;
this_rq->nr_load_updates++;
if (unlikely(!(sysctl_sched_features & SCHED_FEAT_PRECISE_CPU_LOAD)))
goto do_avg;
/* Update delta_fair/delta_exec fields first */
update_curr_load(this_rq);
fair_delta64 = ls->delta_fair + 1;
ls->delta_fair = 0;
exec_delta64 = ls->delta_exec + 1;
ls->delta_exec = 0;
sample_interval64 = this_rq->clock - ls->load_update_last;
ls->load_update_last = this_rq->clock;
if ((s64)sample_interval64 < (s64)TICK_NSEC)
sample_interval64 = TICK_NSEC;
if (exec_delta64 > sample_interval64)
exec_delta64 = sample_interval64;
idle_delta64 = sample_interval64 - exec_delta64;
======> tmp64 = div64_64(SCHED_LOAD_SCALE * exec_delta64, fair_delta64);
tmp64 = div64_64(tmp64 * exec_delta64, sample_interval64);
this_load = (unsigned long)tmp64;
do_avg:
/* Update our load: */
for (i = 0, scale = 1; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
unsigned long old_load, new_load;
/* scale is effectively 1 << i now, and >> i divides by scale */
old_load = this_rq->cpu_load[i];
new_load = this_load;
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) >> i;
}
}
For stable only; the code has been removed in 2.6.24.
Signed-off-by: Chuck Ebbert <[email protected]>
Acked-by: Ingo Molnar <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/sched_fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -93,7 +93,7 @@ unsigned int sysctl_sched_features __rea
SCHED_FEAT_FAIR_SLEEPERS *1 |
SCHED_FEAT_SLEEPER_AVG *0 |
SCHED_FEAT_SLEEPER_LOAD_AVG *1 |
- SCHED_FEAT_PRECISE_CPU_LOAD *1 |
+ SCHED_FEAT_PRECISE_CPU_LOAD *0 |
SCHED_FEAT_START_DEBIT *1 |
SCHED_FEAT_SKIP_INITIAL *0;
--
-
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