rv: Allow to configure the number of per-task monitor

Now that there are 2 monitors for real-time applications, users may want to
enable both of them simultaneously. Make the number of per-task monitor
configurable. Default it to 2 for now.

Cc: John Ogness <john.ogness@linutronix.de>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/93e83313fc4ba7f6e66f4abe80ca5f5494d658d0.1752088709.git.namcao@linutronix.de
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Author: covanam

include/linux/rv.h

@@ -75,14 +75,7 @@ struct ltl_monitor {};
 
 #endif /* CONFIG_RV_LTL_MONITOR */
 
-/*
- * Per-task RV monitors count. Nowadays fixed in RV_PER_TASK_MONITORS.
- * If we find justification for more monitors, we can think about
- * adding more or developing a dynamic method. So far, none of
- * these are justified.
- */
-#define RV_PER_TASK_MONITORS		1
-#define RV_PER_TASK_MONITOR_INIT	(RV_PER_TASK_MONITORS)
+#define RV_PER_TASK_MONITOR_INIT	(CONFIG_RV_PER_TASK_MONITORS)
 
 union rv_task_monitor {
 	struct da_monitor	da_mon;

include/linux/sched.h

@@ -1642,12 +1642,10 @@ struct task_struct {
 
 #ifdef CONFIG_RV
 	/*
-	 * Per-task RV monitor. Nowadays fixed in RV_PER_TASK_MONITORS.
-	 * If we find justification for more monitors, we can think
-	 * about adding more or developing a dynamic method. So far,
-	 * none of these are justified.
+	 * Per-task RV monitor, fixed in CONFIG_RV_PER_TASK_MONITORS.
+	 * If memory becomes a concern, we can think about a dynamic method.
 	 */
-	union rv_task_monitor		rv[RV_PER_TASK_MONITORS];
+	union rv_task_monitor		rv[CONFIG_RV_PER_TASK_MONITORS];
 #endif
 
 #ifdef CONFIG_USER_EVENTS

kernel/trace/rv/Kconfig

@@ -32,6 +32,15 @@ menuconfig RV
 	  For further information, see:
 	    Documentation/trace/rv/runtime-verification.rst
 
+config RV_PER_TASK_MONITORS
+	int "Maximum number of per-task monitor"
+	depends on RV
+	range 1 8
+	default 2
+	help
+	  This option configures the maximum number of per-task RV monitors that can run
+	  simultaneously.
+
 source "kernel/trace/rv/monitors/wip/Kconfig"
 source "kernel/trace/rv/monitors/wwnr/Kconfig"
 source "kernel/trace/rv/monitors/sched/Kconfig"

kernel/trace/rv/monitors/rtapp/Kconfig

@@ -1,5 +1,6 @@
 config RV_MON_RTAPP
 	depends on RV
+	depends on RV_PER_TASK_MONITORS >= 2
 	bool "rtapp monitor"
 	help
 	  Collection of monitors to check for common problems with real-time

kernel/trace/rv/rv.c

@@ -165,20 +165,20 @@ struct dentry *get_monitors_root(void)
 LIST_HEAD(rv_monitors_list);
 
 static int task_monitor_count;
-static bool task_monitor_slots[RV_PER_TASK_MONITORS];
+static bool task_monitor_slots[CONFIG_RV_PER_TASK_MONITORS];
 
 int rv_get_task_monitor_slot(void)
 {
 	int i;
 
 	lockdep_assert_held(&rv_interface_lock);
 
-	if (task_monitor_count == RV_PER_TASK_MONITORS)
+	if (task_monitor_count == CONFIG_RV_PER_TASK_MONITORS)
 		return -EBUSY;
 
 	task_monitor_count++;
 
-	for (i = 0; i < RV_PER_TASK_MONITORS; i++) {
+	for (i = 0; i < CONFIG_RV_PER_TASK_MONITORS; i++) {
 		if (task_monitor_slots[i] == false) {
 			task_monitor_slots[i] = true;
 			return i;
@@ -194,7 +194,7 @@ void rv_put_task_monitor_slot(int slot)
 {
 	lockdep_assert_held(&rv_interface_lock);
 
-	if (slot < 0 || slot >= RV_PER_TASK_MONITORS) {
+	if (slot < 0 || slot >= CONFIG_RV_PER_TASK_MONITORS) {
 		WARN_ONCE(1, "RV releasing an invalid slot!: %d\n", slot);
 		return;
 	}