Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit e37b6a7b authored by Paul Turner's avatar Paul Turner Committed by Ingo Molnar
Browse files

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: default avatarPaul Turner <pjt@google.com>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110122044851.734245014@google.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 6663050e

kernel/sched_fair.c

+3 −3
Original line number Original line Diff line number Diff line
@@ -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)

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;

	int idx, this_cpu, prev_cpu;

	unsigned long tl_per_task;

	unsigned long tl_per_task;

	struct task_group *tg;

	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

	 * Otherwise check if either cpus are near enough in load to allow this

	 * task to be woken on this_cpu.

	 * task to be woken on this_cpu.

	 */

	 */

	if (this_load) {

	if (this_load > 0) {

		unsigned long this_eff_load, prev_eff_load;

		s64 this_eff_load, prev_eff_load;





		this_eff_load = 100;

		this_eff_load = 100;

		this_eff_load *= power_of(prev_cpu);

		this_eff_load *= power_of(prev_cpu);