From 07f06cb3b5f6bd21374a48dbefdb431d71d53974 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 9 Oct 2015 18:00:54 +0200 Subject: [PATCH] sched: Start stopper early 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) Signed-off-by: Oleg Nesterov Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Linus Torvalds Cc: Mike Galbraith Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Rik van Riel Cc: Tejun Heo Cc: Thomas Gleixner Cc: heiko.carstens@de.ibm.com Link: http://lkml.kernel.org/r/20151009160054.GA10176@redhat.com Signed-off-by: Ingo Molnar --- kernel/cpu.c | 1 - kernel/sched/core.c | 12 +++++++++--- 2 files changed, 9 insertions(+), 4 deletions(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 6467521..c85df27 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -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; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f45a7c7..7ee8cae 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -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. */ + set_cpu_active(cpu, true); + stop_machine_unpark(cpu); + return NOTIFY_OK; + case CPU_DOWN_FAILED: - set_cpu_active((long)hcpu, true); + set_cpu_active(cpu, true); return NOTIFY_OK; + default: return NOTIFY_DONE; } -- 2.7.4