From: Peter Zijlstra <peterz@infradead.org>
Date: Wed, 4 Nov 2015 16:22:05 +0000 (-0800)
Subject: rcu: Move wakeup out from under rnp->lock
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=e11f13355b09df970495c45ed0eac1dc85dcf5c1;p=linux-beck.git

rcu: Move wakeup out from under rnp->lock

This patch removes a potential deadlock hazard by moving the
wake_up_process() in rcu_spawn_gp_kthread() out from under rnp->lock.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 40940b0d0310..87b604d0b0d2 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4319,8 +4319,8 @@ static int __init rcu_spawn_gp_kthread(void)
 			sp.sched_priority = kthread_prio;
 			sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
 		}
-		wake_up_process(t);
 		raw_spin_unlock_irqrestore(&rnp->lock, flags);
+		wake_up_process(t);
 	}
 	rcu_spawn_nocb_kthreads();
 	rcu_spawn_boost_kthreads();