linux-kernel - [PATCH 3/3] rv: Add explicit lockdep context for reactors

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Message-Id: <20251014-rv-lockdep-v1-3-0b9e51919ea8@linutronix.de>
Date: Tue, 14 Oct 2025 07:51:58 +0200
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Steven Rostedt <rostedt@...dmis.org>, 
 Gabriele Monaco <gmonaco@...hat.com>, 
 Masami Hiramatsu <mhiramat@...nel.org>, 
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
 Nam Cao <namcao@...utronix.de>
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [PATCH 3/3] rv: Add explicit lockdep context for reactors

Reactors can be called from any context through tracepoints.
When developing reactors care needs to be taken to only call APIs which
are safe. As the tracepoints used during testing may not actually be
called from restrictive contexts lockdep may not be helpful.

Add explicit overrides to help lockdep find invalid code patterns.

The usage of LD_WAIT_FREE will trigger lockdep warnings in the panic
reactor. These are indeed valid warnings but they are out of scope for
RV and will instead be fixed by the printk subsystem.

Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
---
 kernel/trace/rv/rv_reactors.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/trace/rv/rv_reactors.c b/kernel/trace/rv/rv_reactors.c
index 8c02426bc3bd944265f809e431283d1a20d56a8c..d9d335ae9badaa320f1d35dd159a033c3a30eb1a 100644
--- a/kernel/trace/rv/rv_reactors.c
+++ b/kernel/trace/rv/rv_reactors.c
@@ -61,6 +61,7 @@
  *      printk
  */
 
+#include <linux/lockdep.h>
 #include <linux/slab.h>
 
 #include "rv.h"
@@ -480,6 +481,7 @@ int init_rv_reactors(struct dentry *root_dir)
 
 void rv_react(struct rv_monitor *monitor, const char *msg, ...)
 {
+	static DEFINE_WAIT_OVERRIDE_MAP(rv_react_map, LD_WAIT_FREE);
 	va_list args;
 
 	if (!rv_reacting_on() || !monitor->react)
@@ -487,7 +489,9 @@ void rv_react(struct rv_monitor *monitor, const char *msg, ...)
 
 	va_start(args, msg);
 
+	lock_map_acquire_try(&rv_react_map);
 	monitor->react(msg, args);
+	lock_map_release(&rv_react_map);
 
 	va_end(args);
 }

-- 
2.51.0