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sched: Start stopper early

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Ensure the stopper thread is active 'early', because the load balancer
pretty much assumes that its available. And when 'online && active' the
load-balancer is fully available.

Not only the numa balancing stop_two_cpus() caller relies on it, but
also the self migration stuff does, and at CPU_ONLINE time the cpu
really is 'free' to run anything.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: heiko.carstens@de.ibm.com
Link: http://lkml.kernel.org/r/20151009160054.GA10176@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2015-10-09 18:00:54 +02:00 committed by Ingo Molnar
parent f0cf16cbd0
commit 07f06cb3b5
2 changed files with 10 additions and 5 deletions
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1
kernel/cpu.c
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@ -475,7 +475,6 @@ static int smpboot_thread_call(struct notifier_block *nfb,
case CPU_DOWN_FAILED:
case CPU_ONLINE:
stop_machine_unpark(cpu);
smpboot_unpark_threads(cpu);
break;

14
kernel/sched/core.c
View File

@ -5545,21 +5545,27 @@ static void set_cpu_rq_start_time(void)
static int sched_cpu_active(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
int cpu = (long)hcpu;
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_STARTING:
set_cpu_rq_start_time();
return NOTIFY_OK;
case CPU_ONLINE:
/*
* At this point a starting CPU has marked itself as online via
* set_cpu_online(). But it might not yet have marked itself
* as active, which is essential from here on.
*
* Thus, fall-through and help the starting CPU along.
*/
case CPU_DOWN_FAILED:
set_cpu_active((long)hcpu, true);
set_cpu_active(cpu, true);
stop_machine_unpark(cpu);
return NOTIFY_OK;
case CPU_DOWN_FAILED:
set_cpu_active(cpu, true);
return NOTIFY_OK;
default:
return NOTIFY_DONE;
}