[RFC PATCH 06/20] rv: Add rv_get_monitor_by_name()

[Gabriele Monaco <gmonaco@redhat.com>]

Add a helper function to get the rv_monitor pointer for a registered
monitor given its name and add its first user in rv_register_monitor().

Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
---
 kernel/trace/rv/rv.c | 28 +++++++++++++++++++---------
 kernel/trace/rv/rv.h |  1 +
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/kernel/trace/rv/rv.c b/kernel/trace/rv/rv.c
index f77c5865f41a..33919c5fbd6a 100644
--- a/kernel/trace/rv/rv.c
+++ b/kernel/trace/rv/rv.c
@@ -142,6 +142,7 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/rculist.h>
 
 #ifdef CONFIG_RV_MON_EVENTS
 #define CREATE_TRACE_POINTS
@@ -229,6 +230,18 @@ bool rv_is_container_monitor(struct rv_monitor *mon)
 	return next->parent == mon || !mon->enable;
 }
 
+struct rv_monitor *rv_get_monitor_by_name(const char *name)
+{
+	struct rv_monitor *m;
+
+	list_for_each_entry_rcu(m, &rv_monitors_list, list,
+				lockdep_is_held(&rv_interface_lock)) {
+		if (strcmp(name, m->name) == 0)
+			return m;
+	}
+	return NULL;
+}
+
 /*
  * This section collects the monitor/ files and folders.
  */
@@ -753,7 +766,6 @@ static void destroy_monitor_dir(struct rv_monitor *mon)
  */
 int rv_register_monitor(struct rv_monitor *monitor, struct rv_monitor *parent)
 {
-	struct rv_monitor *r;
 	int retval = 0;
 
 	if (strnlen(monitor->name, MAX_RV_MONITOR_NAME_SIZE) == MAX_RV_MONITOR_NAME_SIZE) {
@@ -764,11 +776,9 @@ int rv_register_monitor(struct rv_monitor *monitor, struct rv_monitor *parent)
 
 	guard(mutex)(&rv_interface_lock);
 
-	list_for_each_entry(r, &rv_monitors_list, list) {
-		if (strcmp(monitor->name, r->name) == 0) {
-			pr_info("Monitor %s is already registered\n", monitor->name);
-			return -EEXIST;
-		}
+	if (rv_get_monitor_by_name(monitor->name)) {
+		pr_info("Monitor %s is already registered\n", monitor->name);
+		return -EEXIST;
 	}
 
 	if (parent && rv_is_nested_monitor(parent)) {
@@ -785,9 +795,9 @@ int rv_register_monitor(struct rv_monitor *monitor, struct rv_monitor *parent)
 
 	/* keep children close to the parent for easier visualisation */
 	if (parent)
-		list_add(&monitor->list, &parent->list);
+		list_add_rcu(&monitor->list, &parent->list);
 	else
-		list_add_tail(&monitor->list, &rv_monitors_list);
+		list_add_tail_rcu(&monitor->list, &rv_monitors_list);
 
 	return 0;
 }
@@ -803,7 +813,7 @@ int rv_unregister_monitor(struct rv_monitor *monitor)
 	guard(mutex)(&rv_interface_lock);
 
 	rv_disable_monitor(monitor);
-	list_del(&monitor->list);
+	list_del_rcu(&monitor->list);
 	destroy_monitor_dir(monitor);
 
 	return 0;
diff --git a/kernel/trace/rv/rv.h b/kernel/trace/rv/rv.h
index 07512046e5cc..4d2c9cb284c9 100644
--- a/kernel/trace/rv/rv.h
+++ b/kernel/trace/rv/rv.h
@@ -27,6 +27,7 @@ int rv_disable_monitor(struct rv_monitor *mon);
 int rv_enable_monitor(struct rv_monitor *mon);
 bool rv_is_container_monitor(struct rv_monitor *mon);
 bool rv_is_nested_monitor(struct rv_monitor *mon);
+struct rv_monitor *rv_get_monitor_by_name(const char *name);
 
 #ifdef CONFIG_RV_REACTORS
 int reactor_populate_monitor(struct rv_monitor *mon, struct dentry *root);
-- 
2.55.0