path: root/kernel
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authorPaul Turner <pjt@google.com>2011-01-21 20:44:59 -0800
committerIngo Molnar <mingo@elte.hu>2011-01-26 12:31:01 +0100
commite37b6a7b27b400c3aa488db8c6629a05095bc79c (patch)
treeb27ed41b74eb7e69d2e6b02cc659c4fab3ef12ef /kernel
parent6663050edd9c2e8b1e1f55c09459144d84c045f0 (diff)
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')
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);