rcu: Allow expedited grace periods to be disabled at init
Expedited grace periods can speed up boot, but are undesirable in
aggressive real-time systems. This commit therefore introduces a
kernel parameter rcupdate.rcu_normal_after_boot that disables
expedited grace periods just before init is spawned.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 8fccda3..12b91f5 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -63,6 +63,9 @@
module_param(rcu_expedited, int, 0);
module_param(rcu_normal, int, 0);
+static int rcu_normal_after_boot;
+module_param(rcu_normal_after_boot, int, 0);
+
#if defined(CONFIG_DEBUG_LOCK_ALLOC) && defined(CONFIG_PREEMPT_COUNT)
/**
* rcu_read_lock_sched_held() - might we be in RCU-sched read-side critical section?
@@ -178,6 +181,8 @@
{
if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT))
rcu_unexpedite_gp();
+ if (rcu_normal_after_boot)
+ WRITE_ONCE(rcu_normal, 1);
}
#ifdef CONFIG_PREEMPT_RCU
