From d9f1bb6ad7fc53c406706f47858dd5ff030b14a3 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 25 Feb 2010 14:06:47 -0800 Subject: [PATCH 1/1] rcu: Make rcu_read_lock_sched_held() take boot time into account Before the scheduler starts, all tasks are non-preemptible by definition. So, during that time, rcu_read_lock_sched_held() needs to always return "true". This patch makes that be so. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: mathieu.desnoyers@polymtl.ca Cc: josh@joshtriplett.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: Valdis.Kletnieks@vt.edu Cc: dhowells@redhat.com LKML-Reference: <1267135607-7056-2-git-send-email-paulmck@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 4 +++- include/linux/rcutiny.h | 4 ---- include/linux/rcutree.h | 1 - kernel/rcupdate.c | 18 ++++++++++++++++++ kernel/rcutree.c | 19 ------------------- 5 files changed, 21 insertions(+), 25 deletions(-) diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 1a4de31bd7b4..fcea332a8424 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -62,6 +62,8 @@ extern int sched_expedited_torture_stats(char *page); /* Internal to kernel */ extern void rcu_init(void); +extern int rcu_scheduler_active; +extern void rcu_scheduler_starting(void); #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) #include @@ -140,7 +142,7 @@ static inline int rcu_read_lock_sched_held(void) if (debug_locks) lockdep_opinion = lock_is_held(&rcu_sched_lock_map); - return lockdep_opinion || preempt_count() != 0; + return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active; } #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index 2b70d4e37383..a5195875480a 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -105,10 +105,6 @@ static inline void rcu_exit_nohz(void) #endif /* #else #ifdef CONFIG_NO_HZ */ -static inline void rcu_scheduler_starting(void) -{ -} - static inline void exit_rcu(void) { } diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 704a010f686c..42cc3a04779e 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -35,7 +35,6 @@ struct notifier_block; extern void rcu_sched_qs(int cpu); extern void rcu_bh_qs(int cpu); extern int rcu_needs_cpu(int cpu); -extern void rcu_scheduler_starting(void); extern int rcu_expedited_torture_stats(char *page); #ifdef CONFIG_TREE_PREEMPT_RCU diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 033cb55c26df..7bfa004572b1 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -44,6 +44,7 @@ #include #include #include +#include #ifdef CONFIG_DEBUG_LOCK_ALLOC static struct lock_class_key rcu_lock_key; @@ -62,6 +63,23 @@ struct lockdep_map rcu_sched_lock_map = EXPORT_SYMBOL_GPL(rcu_sched_lock_map); #endif +int rcu_scheduler_active __read_mostly; + +/* + * This function is invoked towards the end of the scheduler's initialization + * process. Before this is called, the idle task might contain + * RCU read-side critical sections (during which time, this idle + * task is booting the system). After this function is called, the + * idle tasks are prohibited from containing RCU read-side critical + * sections. + */ +void rcu_scheduler_starting(void) +{ + WARN_ON(num_online_cpus() != 1); + WARN_ON(nr_context_switches() > 0); + rcu_scheduler_active = 1; +} + /* * Awaken the corresponding synchronize_rcu() instance now that a * grace period has elapsed. diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 525d39810616..335bfe4f0076 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -46,7 +46,6 @@ #include #include #include -#include #include "rcutree.h" @@ -81,9 +80,6 @@ DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); -static int rcu_scheduler_active __read_mostly; - - /* * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s * permit this function to be invoked without holding the root rcu_node @@ -1565,21 +1561,6 @@ static int rcu_needs_cpu_quick_check(int cpu) rcu_preempt_needs_cpu(cpu); } -/* - * This function is invoked towards the end of the scheduler's initialization - * process. Before this is called, the idle task might contain - * RCU read-side critical sections (during which time, this idle - * task is booting the system). After this function is called, the - * idle tasks are prohibited from containing RCU read-side critical - * sections. - */ -void rcu_scheduler_starting(void) -{ - WARN_ON(num_online_cpus() != 1); - WARN_ON(nr_context_switches() > 0); - rcu_scheduler_active = 1; -} - static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; static atomic_t rcu_barrier_cpu_count; static DEFINE_MUTEX(rcu_barrier_mutex); -- 2.34.1