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| author | Paul Turner <pjt@google.com> | 2011-01-21 20:44:59 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-01-26 12:31:01 +0100 |
| commit | e37b6a7b27b400c3aa488db8c6629a05095bc79c (patch) | |
| tree | b27ed41b74eb7e69d2e6b02cc659c4fab3ef12ef /kernel/sched_fair.c | |
| parent | 6663050edd9c2e8b1e1f55c09459144d84c045f0 (diff) | |
| download | lwn-e37b6a7b27b400c3aa488db8c6629a05095bc79c.tar.gz lwn-e37b6a7b27b400c3aa488db8c6629a05095bc79c.zip | |
sched: Fix sign under-flows in wake_affine
While care is taken around the zero-point in effective_load to not exceed
the instantaneous rq->weight, it's still possible (e.g. using wake_idx != 0)
for (load + effective_load) to underflow.
In this case the comparing the unsigned values can result in incorrect balanced
decisions.
Signed-off-by: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110122044851.734245014@google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
| -rw-r--r-- | kernel/sched_fair.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 354769979c02..ccecfec02a70 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1432,7 +1432,7 @@ static inline unsigned long effective_load(struct task_group *tg, int cpu, static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) { - unsigned long this_load, load; + s64 this_load, load; int idx, this_cpu, prev_cpu; unsigned long tl_per_task; struct task_group *tg; @@ -1471,8 +1471,8 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) * Otherwise check if either cpus are near enough in load to allow this * task to be woken on this_cpu. */ - if (this_load) { - unsigned long this_eff_load, prev_eff_load; + if (this_load > 0) { + s64 this_eff_load, prev_eff_load; this_eff_load = 100; this_eff_load *= power_of(prev_cpu); |