From 2124fd9572e3939cadd535631542398b36c022f4 Mon Sep 17 00:00:00 2001 From: Tiejun Chen Date: Thu, 7 Nov 2013 10:06:07 +0800 Subject: [PATCH 285/352] cpu_down: move migrate_enable() back Commit 08c1ab68, "hotplug-use-migrate-disable.patch", intends to use migrate_enable()/migrate_disable() to replace that combination of preempt_enable() and preempt_disable(), but actually in !CONFIG_PREEMPT_RT_FULL case, migrate_enable()/migrate_disable() are still equal to preempt_enable()/preempt_disable(). So that followed cpu_hotplug_begin()/cpu_unplug_begin(cpu) would go schedule() to trigger schedule_debug() like this: _cpu_down() | + migrate_disable() = preempt_disable() | + cpu_hotplug_begin() or cpu_unplug_begin() | + schedule() | + __schedule() | + preempt_disable(); | + __schedule_bug() is true! So we should move migrate_enable() as the original scheme. Signed-off-by: Tiejun Chen --- kernel/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index cd25dbb..bb5cde2 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -1310,6 +1310,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, goto restore_cpus; } + migrate_enable(); cpu_hotplug_begin(); ret = cpu_unplug_begin(cpu); if (ret) { @@ -1357,7 +1358,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen, cpu_unplug_done(cpu); out_cancel: cpu_hotplug_done(); - migrate_enable(); /* This post dead nonsense must die */ if (!ret && hasdied) cpu_notify_nofail(CPU_POST_DEAD, cpu); -- 2.7.4