rcu: Clean up code based on review feedback from Josh Triplett

[firefly-linux-kernel-4.4.55.git] / kernel / rcutree_plugin.h

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 1cee04f627eb2631aab0083e5eebe02e6be394be..8ff1ba7b3c432f37e7f5cbdc1ef972a40c75368c 100644 (file)
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -150,6 +150,16 @@ void __rcu_read_lock(void)
 }
 EXPORT_SYMBOL_GPL(__rcu_read_lock);
 
+/*
+ * Check for preempted RCU readers blocking the current grace period
+ * for the specified rcu_node structure.  If the caller needs a reliable
+ * answer, it must hold the rcu_node's ->lock.
+ */
+static int rcu_preempted_readers(struct rcu_node *rnp)
+{
+       return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
+}
+
 static void rcu_read_unlock_special(struct task_struct *t)
 {
        int empty;
@@ -196,7 +206,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
                                break;
                        spin_unlock(&rnp->lock);  /* irqs remain disabled. */
                }
-               empty = list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
+               empty = !rcu_preempted_readers(rnp);
                list_del_init(&t->rcu_node_entry);
                t->rcu_blocked_node = NULL;
 
@@ -207,7 +217,7 @@ static void rcu_read_unlock_special(struct task_struct *t)
                 * drop rnp->lock and restore irq.
                 */
                if (!empty && rnp->qsmask == 0 &&
-                   list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1])) {
+                   !rcu_preempted_readers(rnp)) {
                        struct rcu_node *rnp_p;
 
                        if (rnp->parent == NULL) {
@@ -257,12 +267,12 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
 {
        unsigned long flags;
        struct list_head *lp;
-       int phase = rnp->gpnum & 0x1;
+       int phase;
        struct task_struct *t;
 
-       if (!list_empty(&rnp->blocked_tasks[phase])) {
+       if (rcu_preempted_readers(rnp)) {
                spin_lock_irqsave(&rnp->lock, flags);
-               phase = rnp->gpnum & 0x1; /* re-read under lock. */
+               phase = rnp->gpnum & 0x1;
                lp = &rnp->blocked_tasks[phase];
                list_for_each_entry(t, lp, rcu_node_entry)
                        printk(" P%d", t->pid);
@@ -281,20 +291,10 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
  */
 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
 {
-       WARN_ON_ONCE(!list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]));
+       WARN_ON_ONCE(rcu_preempted_readers(rnp));
        WARN_ON_ONCE(rnp->qsmask);
 }
 
-/*
- * Check for preempted RCU readers for the specified rcu_node structure.
- * If the caller needs a reliable answer, it must hold the rcu_node's
- * >lock.
- */
-static int rcu_preempted_readers(struct rcu_node *rnp)
-{
-       return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]);
-}
-
 #ifdef CONFIG_HOTPLUG_CPU
 
 /*
@@ -461,6 +461,15 @@ static void rcu_preempt_note_context_switch(int cpu)
 {
 }
 
+/*
+ * Because preemptable RCU does not exist, there are never any preempted
+ * RCU readers.
+ */
+static int rcu_preempted_readers(struct rcu_node *rnp)
+{
+       return 0;
+}
+
 #ifdef CONFIG_RCU_CPU_STALL_DETECTOR
 
 /*
@@ -483,15 +492,6 @@ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
        WARN_ON_ONCE(rnp->qsmask);
 }
 
-/*
- * Because preemptable RCU does not exist, there are never any preempted
- * RCU readers.
- */
-static int rcu_preempted_readers(struct rcu_node *rnp)
-{
-       return 0;
-}
-
 #ifdef CONFIG_HOTPLUG_CPU
 
 /*