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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2009-11-27 08:12:25 -0500
committerIngo Molnar <mingo@elte.hu>2009-12-09 04:03:03 -0500
commit5afcdab706d6002cb02b567ba46e650215e694e8 (patch)
tree015c3fb61dc8a4217bc83927efd7882e7d494d2b
parent970b13bacba14a8cef6f642861947df1d175b0b3 (diff)
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: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched.c13
1 files changed, 1 insertions, 12 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 01fd131b47a4..1f9c6d99f15d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2060,23 +2060,12 @@ task_hot(struct task_struct *p, u64 now, struct sched_domain *sd)
2060void set_task_cpu(struct task_struct *p, unsigned int new_cpu) 2060void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
2061{ 2061{
2062 int old_cpu = task_cpu(p); 2062 int old_cpu = task_cpu(p);
2063 struct rq *old_rq = cpu_rq(old_cpu), *new_rq = cpu_rq(new_cpu); 2063 struct rq *old_rq = cpu_rq(old_cpu);
2064 struct cfs_rq *old_cfsrq = task_cfs_rq(p), 2064 struct cfs_rq *old_cfsrq = task_cfs_rq(p),
2065 *new_cfsrq = cpu_cfs_rq(old_cfsrq, new_cpu); 2065 *new_cfsrq = cpu_cfs_rq(old_cfsrq, new_cpu);
2066 u64 clock_offset;
2067
2068 clock_offset = old_rq->clock - new_rq->clock;
2069 2066
2070 trace_sched_migrate_task(p, new_cpu); 2067 trace_sched_migrate_task(p, new_cpu);
2071 2068
2072#ifdef CONFIG_SCHEDSTATS
2073 if (p->se.wait_start)
2074 p->se.wait_start -= clock_offset;
2075 if (p->se.sleep_start)
2076 p->se.sleep_start -= clock_offset;
2077 if (p->se.block_start)
2078 p->se.block_start -= clock_offset;
2079#endif
2080 if (old_cpu != new_cpu) { 2069 if (old_cpu != new_cpu) {
2081 p->se.nr_migrations++; 2070 p->se.nr_migrations++;
2082#ifdef CONFIG_SCHEDSTATS 2071#ifdef CONFIG_SCHEDSTATS