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Commit 5afcdab7 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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sched: Remove rq->clock coupling from set_task_cpu() 



set_task_cpu() should be rq invariant and only touch task state, it
currently fails to do so, which opens up a few races, since not all
callers hold both rq->locks.

Remove the relyance on rq->clock, as any site calling set_task_cpu()
should also do a remote clock update, which should ensure the observed
time between these two cpus is monotonic, as per
kernel/sched_clock.c:sched_clock_remote().

Therefore we can simply remove the clock_offset bits and be happy.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 970b13ba

kernel/sched.c

+1 −12
Original line number Diff line number Diff line
@@ -2060,23 +2060,12 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd) 
void set_task_cpu(struct task_struct *p, unsigned int new_cpu)

{

	int old_cpu = task_cpu(p);

	struct rq *old_rq = cpu_rq(old_cpu), *new_rq = cpu_rq(new_cpu);

	struct rq *old_rq = cpu_rq(old_cpu);

	struct cfs_rq *old_cfsrq = task_cfs_rq(p),

		      *new_cfsrq = cpu_cfs_rq(old_cfsrq, new_cpu);

	u64 clock_offset;



	clock_offset = old_rq->clock - new_rq->clock;



	trace_sched_migrate_task(p, new_cpu);



#ifdef CONFIG_SCHEDSTATS

	if (p->se.wait_start)

		p->se.wait_start -= clock_offset;

	if (p->se.sleep_start)

		p->se.sleep_start -= clock_offset;

	if (p->se.block_start)

		p->se.block_start -= clock_offset;

#endif

	if (old_cpu != new_cpu) {

		p->se.nr_migrations++;

#ifdef CONFIG_SCHEDSTATS