rcu: Define rcu_all_qs() only in !PREEMPT builds

Now that rcu_all_qs() is used only in !PREEMPT builds, move it to
tree_plugin.h so that it is defined only in those builds.  This in
turn means that rcu_momentary_dyntick_idle() is only used in !PREEMPT
builds, but it is simply marked __maybe_unused in order to keep it
near the rest of the dyntick-idle code.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index d09a9ab..7f83179 100644 (file)
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -66,7 +66,9 @@ void rcu_scheduler_starting(void);
 extern int rcu_scheduler_active __read_mostly;
 void rcu_end_inkernel_boot(void);
 bool rcu_is_watching(void);
+#ifndef CONFIG_PREEMPT
 void rcu_all_qs(void);
+#endif
 
 /* RCUtree hotplug events */
 int rcutree_prepare_cpu(unsigned int cpu);

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index c8761e7..e140aaa 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -356,7 +356,7 @@ bool rcu_eqs_special_set(int cpu)
  *
  * The caller must have disabled interrupts and must not be idle.
  */
-static void rcu_momentary_dyntick_idle(void)
+static void __maybe_unused rcu_momentary_dyntick_idle(void)
 {
        struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
        int special;
@@ -381,45 +381,6 @@ static int rcu_is_cpu_rrupt_from_idle(void)
               __this_cpu_read(rcu_dynticks.dynticks_nmi_nesting) <= 1;
 }
 
-/*
- * Register an urgently needed quiescent state.  If there is an
- * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight
- * dyntick-idle quiescent state visible to other CPUs, which will in
- * some cases serve for expedited as well as normal grace periods.
- * Either way, register a lightweight quiescent state.
- *
- * The barrier() calls are redundant in the common case when this is
- * called externally, but just in case this is called from within this
- * file.
- *
- */
-void rcu_all_qs(void)
-{
-       unsigned long flags;
-
-       if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs))
-               return;
-       preempt_disable();
-       /* Load rcu_urgent_qs before other flags. */
-       if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) {
-               preempt_enable();
-               return;
-       }
-       this_cpu_write(rcu_dynticks.rcu_urgent_qs, false);
-       barrier(); /* Avoid RCU read-side critical sections leaking down. */
-       if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) {
-               local_irq_save(flags);
-               rcu_momentary_dyntick_idle();
-               local_irq_restore(flags);
-       }
-       if (unlikely(raw_cpu_read(rcu_data.cpu_no_qs.b.exp)))
-               rcu_qs();
-       this_cpu_inc(rcu_dynticks.rcu_qs_ctr);
-       barrier(); /* Avoid RCU read-side critical sections leaking up. */
-       preempt_enable();
-}
-EXPORT_SYMBOL_GPL(rcu_all_qs);
-
 #define DEFAULT_RCU_BLIMIT 10     /* Maximum callbacks per rcu_do_batch. */
 static long blimit = DEFAULT_RCU_BLIMIT;
 #define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */

diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index cd4c1b9..7add1c2 100644 (file)
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -947,6 +947,45 @@ static void rcu_qs(void)
        rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
 }
 
+/*
+ * Register an urgently needed quiescent state.  If there is an
+ * emergency, invoke rcu_momentary_dyntick_idle() to do a heavy-weight
+ * dyntick-idle quiescent state visible to other CPUs, which will in
+ * some cases serve for expedited as well as normal grace periods.
+ * Either way, register a lightweight quiescent state.
+ *
+ * The barrier() calls are redundant in the common case when this is
+ * called externally, but just in case this is called from within this
+ * file.
+ *
+ */
+void rcu_all_qs(void)
+{
+       unsigned long flags;
+
+       if (!raw_cpu_read(rcu_dynticks.rcu_urgent_qs))
+               return;
+       preempt_disable();
+       /* Load rcu_urgent_qs before other flags. */
+       if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) {
+               preempt_enable();
+               return;
+       }
+       this_cpu_write(rcu_dynticks.rcu_urgent_qs, false);
+       barrier(); /* Avoid RCU read-side critical sections leaking down. */
+       if (unlikely(raw_cpu_read(rcu_dynticks.rcu_need_heavy_qs))) {
+               local_irq_save(flags);
+               rcu_momentary_dyntick_idle();
+               local_irq_restore(flags);
+       }
+       if (unlikely(raw_cpu_read(rcu_data.cpu_no_qs.b.exp)))
+               rcu_qs();
+       this_cpu_inc(rcu_dynticks.rcu_qs_ctr);
+       barrier(); /* Avoid RCU read-side critical sections leaking up. */
+       preempt_enable();
+}
+EXPORT_SYMBOL_GPL(rcu_all_qs);
+
 /*
  * Note a PREEMPT=n context switch.  The caller must have disabled interrupts.
  */