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 <paulmck@linux.vnet.ibm.com>
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 <mingo@elte.hu>

3 files changed, 3 insertions, 6 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 <linux/rcutree.h>
@@ -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