linux-kernel - [PATCH RFC -rt] Alleged fix for CPU-hotplug deadlock

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Date:	Tue, 21 Feb 2012 12:00:09 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	rostedt@...dmis.org
Cc:	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH RFC -rt] Alleged fix for CPU-hotplug deadlock

This patch is intended to fix a deadlock seen in -rt.  Untested, might
not even compile.  The intent is to move kthread_stop() outside of
the CPU-hotplug lock, thus preventing deadlocks involving sleeping
spinlocks.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 8c26a49..e0d514b 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -2041,8 +2041,7 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
 		rcu_send_cbs_to_online(&rcu_sched_state);
 		rcu_preempt_send_cbs_to_online();
 		break;
-	case CPU_DEAD:
-	case CPU_DEAD_FROZEN:
+	case CPU_POST_DEAD:
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:
 		rcu_offline_cpu(cpu);

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