rcu: Add boosting to TREE_PREEMPT_RCU tracing

Includes total number of tasks boosted, number boosted on behalf of each
of normal and expedited grace periods, and statistics on attempts to
initiate boosting that failed for various reasons.

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 68 insertions, 0 deletions

diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c
index 1cedf94e2c4f..ead5736f99b5 100644
--- a/kernel/rcutree_trace.c
+++ b/kernel/rcutree_trace.c
@@ -157,6 +157,71 @@ static const struct file_operations rcudata_csv_fops = {
         .release = single_release,
 };
 
+#ifdef CONFIG_RCU_BOOST
+
+static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp)
+{
+        seq_printf(m,  "%d:%d tasks=%c%c%c%c ntb=%lu neb=%lu nnb=%lu "
+                   "j=%04x bt=%04x\n",
+                   rnp->grplo, rnp->grphi,
+                   "T."[list_empty(&rnp->blkd_tasks)],
+                   "N."[!rnp->gp_tasks],
+                   "E."[!rnp->exp_tasks],
+                   "B."[!rnp->boost_tasks],
+                   rnp->n_tasks_boosted, rnp->n_exp_boosts,
+                   rnp->n_normal_boosts,
+                   (int)(jiffies & 0xffff),
+                   (int)(rnp->boost_time & 0xffff));
+        seq_printf(m, "%s: nt=%lu egt=%lu bt=%lu nb=%lu ny=%lu nos=%lu\n",
+                   "     balk",
+                   rnp->n_balk_blkd_tasks,
+                   rnp->n_balk_exp_gp_tasks,
+                   rnp->n_balk_boost_tasks,
+                   rnp->n_balk_notblocked,
+                   rnp->n_balk_notyet,
+                   rnp->n_balk_nos);
+}
+
+static int show_rcu_node_boost(struct seq_file *m, void *unused)
+{
+        struct rcu_node *rnp;
+
+        rcu_for_each_leaf_node(&rcu_preempt_state, rnp)
+                print_one_rcu_node_boost(m, rnp);
+        return 0;
+}
+
+static int rcu_node_boost_open(struct inode *inode, struct file *file)
+{
+        return single_open(file, show_rcu_node_boost, NULL);
+}
+
+static const struct file_operations rcu_node_boost_fops = {
+        .owner = THIS_MODULE,
+        .open = rcu_node_boost_open,
+        .read = seq_read,
+        .llseek = seq_lseek,
+        .release = single_release,
+};
+
+/*
+ * Create the rcuboost debugfs entry.  Standard error return.
+ */
+static int rcu_boost_trace_create_file(struct dentry *rcudir)
+{
+        return !debugfs_create_file("rcuboost", 0444, rcudir, NULL,
+                                    &rcu_node_boost_fops);
+}
+
+#else /* #ifdef CONFIG_RCU_BOOST */
+
+static int rcu_boost_trace_create_file(struct dentry *rcudir)
+{
+        return 0;  /* There cannot be an error if we didn't create it! */
+}
+
+#endif /* #else #ifdef CONFIG_RCU_BOOST */
+
 static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
 {
         unsigned long gpnum;
@@ -315,6 +380,9 @@ static int __init rcutree_trace_init(void)
         if (!retval)
                 goto free_out;
 
+        if (rcu_boost_trace_create_file(rcudir))
+                goto free_out;
+
         retval = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops);
         if (!retval)
                 goto free_out;