linux-kernel - [PATCH 5/6] rv: Remove the nop reactor

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Message-Id: <21a530ffb705887d7aed18255572521e5b880bc0.1753091084.git.namcao@linutronix.de>
Date: Mon, 21 Jul 2025 11:47:12 +0200
From: Nam Cao <namcao@...utronix.de>
To: Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	linux-trace-kernel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Gabriele Monaco <gmonaco@...hat.com>
Cc: Nam Cao <namcao@...utronix.de>
Subject: [PATCH 5/6] rv: Remove the nop reactor

As suggested by the name, the nop reactor does not do anything. It is the
default reactor when nothing else is selected.

However, the monitors already null-check the reactor function pointers.
Thus, instead of a nop reactor, just set the react function pointer to
NULL. The nop reactor can then be removed.

Signed-off-by: Nam Cao <namcao@...utronix.de>
---
 kernel/trace/rv/rv_reactors.c | 63 ++++++-----------------------------
 1 file changed, 11 insertions(+), 52 deletions(-)

diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.c
index a8e849e6cd85..aee622e4b833 100644
--- a/kernel/trace/rv/rv_reactors.c
+++ b/kernel/trace/rv/rv_reactors.c
@@ -70,17 +70,6 @@
  */
 static LIST_HEAD(rv_reactors_list);
 
-static struct rv_reactor *get_reactor_rdef_by_name(char *name)
-{
-	struct rv_reactor *r;
-
-	list_for_each_entry(r, &rv_reactors_list, list) {
-		if (strcmp(name, r->name) == 0)
-			return r;
-	}
-	return NULL;
-}
-
 /*
  * Available reactors seq functions.
  */
@@ -174,7 +163,7 @@ static void monitor_swap_reactors_single(struct rv_monitor *mon,
 
 	mon->reactor = reactor;
 	mon->reacting = reacting;
-	mon->react = reactor->react;
+	mon->react = reactor ? reactor->react : NULL;
 
 	/* enable only once if iterating through a container */
 	if (monitor_enabled && !nested)
@@ -210,10 +199,15 @@ monitor_reactors_write(struct file *file, const char __user *user_buf,
 	struct rv_reactor *reactor;
 	struct seq_file *seq_f;
 	int retval = -EINVAL;
-	bool enable;
 	char *ptr;
 	int len;
 
+	/*
+	 * See monitor_reactors_open()
+	 */
+	seq_f = file->private_data;
+	mon = seq_f->private;
+
 	if (count < 1 || count > MAX_RV_REACTOR_NAME_SIZE + 1)
 		return -EINVAL;
 
@@ -226,14 +220,10 @@ monitor_reactors_write(struct file *file, const char __user *user_buf,
 	ptr = strim(buff);
 
 	len = strlen(ptr);
-	if (!len)
+	if (!len) {
+		monitor_swap_reactors(mon, NULL, false);
 		return count;
-
-	/*
-	 * See monitor_reactors_open()
-	 */
-	seq_f = file->private_data;
-	mon = seq_f->private;
+	}
 
 	mutex_lock(&rv_interface_lock);
 
@@ -243,12 +233,7 @@ monitor_reactors_write(struct file *file, const char __user *user_buf,
 		if (strcmp(ptr, reactor->name) != 0)
 			continue;
 
-		if (strcmp(reactor->name, "nop"))
-			enable = false;
-		else
-			enable = true;
-
-		monitor_swap_reactors(mon, reactor, enable);
+		monitor_swap_reactors(mon, reactor, true);
 
 		retval = count;
 		break;
@@ -435,32 +420,12 @@ int reactor_populate_monitor(struct rv_monitor *mon)
 	if (!tmp)
 		return -ENOMEM;
 
-	/*
-	 * Configure as the rv_nop reactor.
-	 */
-	mon->reactor = get_reactor_rdef_by_name("nop");
-	mon->reacting = false;
-
 	return 0;
 }
 
-/*
- * Nop reactor register
- */
-__printf(1, 2) static void rv_nop_reaction(const char *msg, ...)
-{
-}
-
-static struct rv_reactor rv_nop = {
-	.name = "nop",
-	.description = "no-operation reactor: do nothing.",
-	.react = rv_nop_reaction
-};
-
 int init_rv_reactors(struct dentry *root_dir)
 {
 	struct dentry *available, *reacting;
-	int retval;
 
 	available = rv_create_file("available_reactors", RV_MODE_READ, root_dir, NULL,
 				   &available_reactors_ops);
@@ -471,16 +436,10 @@ int init_rv_reactors(struct dentry *root_dir)
 	if (!reacting)
 		goto rm_available;
 
-	retval = __rv_register_reactor(&rv_nop);
-	if (retval)
-		goto rm_reacting;
-
 	turn_reacting_on();
 
 	return 0;
 
-rm_reacting:
-	rv_remove(reacting);
 rm_available:
 	rv_remove(available);
 out_err:
-- 
2.39.5