rv: Add option for nested monitors and include sched

Monitors describing complex systems, such as the scheduler, can easily
grow to the point where they are just hard to understand because of the
many possible state transitions.
Often it is possible to break such descriptions into smaller monitors,
sharing some or all events. Enabling those smaller monitors concurrently
is, in fact, testing the system as if we had one single larger monitor.
Splitting models into multiple specification is not only easier to
understand, but gives some more clues when we see errors.

Add the possibility to create container monitors, whose only purpose is
to host other nested monitors. Enabling a container monitor enables all
nested ones, but it's still possible to enable nested monitors
independently.
Add the sched monitor as first container, for now empty.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/20250305140406.350227-3-gmonaco@redhat.com
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

1 files changed, 25 insertions, 3 deletions

diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.c
index 7b49cbe388d4..9501ca886d83 100644
--- a/kernel/trace/rv/rv_reactors.c
+++ b/kernel/trace/rv/rv_reactors.c
@@ -158,8 +158,9 @@ static const struct seq_operations monitor_reactors_seq_ops = {
 	.show	= monitor_reactor_show
 };
 
-static void monitor_swap_reactors(struct rv_monitor_def *mdef, struct rv_reactor_def *rdef,
-				    bool reacting)
+static void monitor_swap_reactors_single(struct rv_monitor_def *mdef,
+					 struct rv_reactor_def *rdef,
+					 bool reacting, bool nested)
 {
 	bool monitor_enabled;
 
@@ -179,10 +180,31 @@ static void monitor_swap_reactors(struct rv_monitor_def *mdef, struct rv_reactor
 	mdef->reacting = reacting;
 	mdef->monitor->react = rdef->reactor->react;
 
-	if (monitor_enabled)
+	/* enable only once if iterating through a container */
+	if (monitor_enabled && !nested)
 		rv_enable_monitor(mdef);
 }
 
+static void monitor_swap_reactors(struct rv_monitor_def *mdef,
+				  struct rv_reactor_def *rdef, bool reacting)
+{
+	struct rv_monitor_def *p = mdef;
+
+	if (rv_is_container_monitor(mdef))
+		list_for_each_entry_continue(p, &rv_monitors_list, list) {
+			if (p->parent != mdef->monitor)
+				break;
+			monitor_swap_reactors_single(p, rdef, reacting, true);
+		}
+	/*
+	 * This call enables and disables the monitor if they were active.
+	 * In case of a container, we already disabled all and will enable all.
+	 * All nested monitors are enabled also if they were off, we may refine
+	 * this logic in the future.
+	 */
+	monitor_swap_reactors_single(mdef, rdef, reacting, false);
+}
+
 static ssize_t
 monitor_reactors_write(struct file *file, const char __user *user_buf,
 		      size_t count, loff_t *ppos)