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-rw-r--r--include/linux/rcupdate.h1
-rw-r--r--init/Kconfig13
-rw-r--r--kernel/rcu/update.c11
3 files changed, 24 insertions, 1 deletions
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 57a4d1f73a00..b9f039b11d31 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -278,6 +278,7 @@ static inline int rcu_preempt_depth(void)
/* Internal to kernel */
void rcu_init(void);
+void rcu_end_inkernel_boot(void);
void rcu_sched_qs(void);
void rcu_bh_qs(void);
void rcu_check_callbacks(int user);
diff --git a/init/Kconfig b/init/Kconfig
index f5dbc6d4261b..9a0592516f48 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -791,6 +791,19 @@ 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 5f850823c187..7b12466f90bc 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -64,7 +64,8 @@ module_param(rcu_expedited, int, 0);
#ifndef CONFIG_TINY_RCU
-static atomic_t rcu_expedited_nesting;
+static atomic_t rcu_expedited_nesting =
+ ATOMIC_INIT(IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT) ? 1 : 0);
/*
* Should normal grace-period primitives be expedited? Intended for
@@ -109,6 +110,14 @@ EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
#endif /* #ifndef CONFIG_TINY_RCU */
+/*
+ * Inform RCU of the end of the in-kernel boot sequence.
+ */
+void rcu_end_inkernel_boot(void)
+{
+ if (IS_ENABLED(CONFIG_RCU_EXPEDITE_BOOT))
+ rcu_unexpedite_gp();
+}
#ifdef CONFIG_PREEMPT_RCU