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From: Tiejun Chen <tiejun.chen@windriver.com>
Subject: cpu_down: move migrate_enable() back
Date: Thu, 7 Nov 2013 10:06:07 +0800
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.9/older/patches-4.9.20-rt16.tar.xz
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()
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+ migrate_disable() = preempt_disable()
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+ cpu_hotplug_begin() or cpu_unplug_begin()
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+ schedule()
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+ __schedule()
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+ preempt_disable();
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+ __schedule_bug() is true!
So we should move migrate_enable() as the original scheme.
Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
---
kernel/cpu.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1195,6 +1195,7 @@ static int __ref _cpu_down(unsigned int
goto restore_cpus;
}
+ migrate_enable();
cpu_hotplug_begin();
ret = cpu_unplug_begin(cpu);
if (ret) {
@@ -1242,7 +1243,6 @@ static int __ref _cpu_down(unsigned int
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);
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