rcu: Make rcu_read_lock_sched_held() handle !PREEMPT

The rcu_read_lock_sched_held() needs to unconditionally return
the value "1" in a !PREEMPT kernel, because under !PREEMPT,
-all- kernel code is implicitly preempt-disabled.  This patch
makes this happen.

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: <1267667418-32233-1-git-send-email-paulmck@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/rcupdate.h

@@ -136,6 +136,7 @@ static inline int rcu_read_lock_bh_held(void)
  * can prove otherwise.  Note that disabling of preemption (including
  * disabling irqs) counts as an RCU-sched read-side critical section.
  */
+#ifdef CONFIG_PREEMPT
 static inline int rcu_read_lock_sched_held(void)
 {
 	int lockdep_opinion = 0;
@@ -144,6 +145,12 @@ static inline int rcu_read_lock_sched_held(void)
 		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
 	return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active;
 }
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+	return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
 
 #else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
@@ -164,10 +171,17 @@ static inline int rcu_read_lock_bh_held(void)
 	return 1;
 }
 
+#ifdef CONFIG_PREEMPT
 static inline int rcu_read_lock_sched_held(void)
 {
 	return preempt_count() != 0 || !rcu_scheduler_active;
 }
+#else /* #ifdef CONFIG_PREEMPT */
+static inline int rcu_read_lock_sched_held(void)
+{
+	return 1;
+}
+#endif /* #else #ifdef CONFIG_PREEMPT */
 
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */