[RFC PATCH 06/10] yield_to(), cpu-hotplug: Prevent offlining of other CPUs properly
From: Srivatsa S. Bhat <hidden>
Date: 2012-12-04 08:58:49
Also in:
lkml
Subsystem:
scheduler, the rest · Maintainers:
Ingo Molnar, Peter Zijlstra, Juri Lelli, Vincent Guittot, Linus Torvalds
With stop_machine() gone from the CPU offline path, we can't depend on local_irq_save() to prevent CPUs from going offline from under us. Use the get/put_online_cpus_stable_atomic() APIs to prevent CPUs from going offline, while invoking from atomic context. And use the stable online mask while interacting with other CPUs. Signed-off-by: Srivatsa S. Bhat <redacted> --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c1a5d93..d0b159b 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c@@ -4312,6 +4312,7 @@ bool __sched yield_to(struct task_struct *p, bool preempt) unsigned long flags; bool yielded = 0; + get_online_cpus_stable_atomic(); local_irq_save(flags); rq = this_rq();
@@ -4339,13 +4340,14 @@ again: * Make p's CPU reschedule; pick_next_entity takes care of * fairness. */ - if (preempt && rq != p_rq) + if (preempt && rq != p_rq && cpu_online_stable(task_cpu(p))) resched_task(p_rq->curr); } out: double_rq_unlock(rq, p_rq); local_irq_restore(flags); + put_online_cpus_stable_atomic(); if (yielded) schedule();