linux-kernel - [PATCH tip/core/rcu 18/40] srcu: Allow early boot use of synchronize

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Date:   Wed, 12 Apr 2017 10:40:03 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH tip/core/rcu 18/40] srcu: Allow early boot use of synchronize_srcu()

This commit checks for pre-scheduler state, and if that early in the
boot process, synchronize_srcu() and friends are no-ops.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
---
 kernel/rcu/srcu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index 6beeba7b0b67..1026ce24922f 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -411,6 +411,8 @@ static void __synchronize_srcu(struct srcu_struct *sp, int trycount)
 			 lock_is_held(&rcu_sched_lock_map),
 			 "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section");
 
+	if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE)
+		return;
 	might_sleep();
 	init_completion(&rcu.completion);
 
-- 
2.5.2