rcu: update: Make RCU_EXPEDITE_BOOT be the default

RCU_EXPEDITE_BOOT should speed up the boot process by enforcing
synchronize_rcu_expedited() instead of synchronize_rcu() during the boot
process. There should be no reason why one does not want this and there
is no need worry about real time latency at this point.
Therefore make it default.

Note that users wishing to avoid expediting entirely, for example when
bringing up new hardware possibly having flaky IPIs, can use the
rcu_normal boot parameter to override boot-time expediting.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
[ paulmck: Reworded commit log. ]
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

diff --git a/init/Kconfig b/init/Kconfig
index 223b734abccdc3b7f3baae457261dd66862fcd1d..96e6d56acd508a12cdd1658eaf8211e446569404 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -781,19 +781,6 @@ config RCU_NOCB_CPU_ALL
 
 endchoice
 
-config RCU_EXPEDITE_BOOT
-       bool
-       default n
-       help
-         This option enables expedited grace periods at boot time,
-         as if rcu_expedite_gp() had been invoked early in boot.
-         The corresponding rcu_unexpedite_gp() is invoked from
-         rcu_end_inkernel_boot(), which is intended to be invoked
-         at the end of the kernel-only boot sequence, just before
-         init is exec'ed.
-
-         Accept the default if unsure.
-
 endmenu # "RCU Subsystem"
 
 config BUILD_BIN2C

diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 4f6db7e6a1179ee00c99f62d854a39b00c959d2b..9e03db9ea9c09c422625537c80a16a020fe0bda0 100644 (file)
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -132,8 +132,7 @@ bool rcu_gp_is_normal(void)
 }
 EXPORT_SYMBOL_GPL(rcu_gp_is_normal);
 
-static atomic_t rcu_expedited_nesting =
-       ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0);
+static atomic_t rcu_expedited_nesting = ATOMIC_INIT(1);
 
 /*
  * Should normal grace-period primitives be expedited?  Intended for
@@ -182,8 +181,7 @@ EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
  */
 void rcu_end_inkernel_boot(void)
 {
-       if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT))
-               rcu_unexpedite_gp();
+       rcu_unexpedite_gp();
        if (rcu_normal_after_boot)
                WRITE_ONCE(rcu_normal, 1);
 }