Messages in this thread Patch in this message | | | From | "Paul E. McKenney" <> | Subject | [PATCH v2 RFC tip/core/rcu 4/4] rcu: Add Kconfig option to expedite grace periods during boot | Date | Thu, 19 Feb 2015 21:09:39 -0800 |
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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
This commit adds a CONFIG_RCU_EXPEDITE_BOOT Kconfig parameter that emulates a very early boot rcu_expedite_gp(). A late-boot call to rcu_end_inkernel_boot() will provide the corresponding rcu_unexpedite_gp(). The late-boot call to rcu_end_inkernel_boot() should be made just before init is spawned.
Reported-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- include/linux/rcupdate.h | 1 + init/Kconfig | 13 +++++++++++++ kernel/rcu/update.c | 11 ++++++++++- 3 files changed, 24 insertions(+), 1 deletion(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 0189ac088c67..573a5afd5ed8 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -287,6 +287,7 @@ 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 1354ac09b516..ece7e9380867 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 44a74c24936a..1f133350da01 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 -- 1.8.1.5
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