From mboxrd@z Thu Jan 1 00:00:00 1970 From: Steven Rostedt Subject: [PATCH RT 1/5] cpu_down: move migrate_enable() back Date: Tue, 10 Dec 2013 19:46:32 -0500 Message-ID: <20131211004643.182742571@goodmis.org> References: <20131211004631.950208564@goodmis.org> Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Tiejun Chen To: linux-kernel@vger.kernel.org, linux-rt-users Return-path: Content-Disposition: inline; filename=0001-cpu_down-move-migrate_enable-back.patch Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org 3.8.13.13-rt26-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Tiejun Chen 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. Cc: stable-rt@vger.kernel.org Signed-off-by: Tiejun Chen Signed-off-by: Steven Rostedt --- kernel/cpu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/cpu.c b/kernel/cpu.c index 98f2ea3..da6e128 100644 --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -594,6 +594,7 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) err = -EBUSY; goto restore_cpus; } + migrate_enable(); cpu_hotplug_begin(); err = cpu_unplug_begin(cpu); @@ -647,7 +648,6 @@ static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) out_release: cpu_unplug_done(cpu); out_cancel: - migrate_enable(); cpu_hotplug_done(); if (!err) cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu); -- 1.8.4.3