linux-kernel - [for-next][PATCH 5/5] rv: Add explicit lockdep context for reactors

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Message-ID: <20251112222007.272818255@kernel.org>
Date: Wed, 12 Nov 2025 17:19:51 -0500
From: Steven Rostedt <rostedt@...nel.org>
To: linux-kernel@...r.kernel.org
Cc: Gabriele Monaco <gmonaco@...hat.com>,
 Nam Cao <namcao@...utronix.de>,
 Thomas Weißschuh <thomas.weissschuh@...utronix.de>
Subject: [for-next][PATCH 5/5] rv: Add explicit lockdep context for reactors

From: =?UTF-8?q?Thomas=20Wei=C3=9Fschuh?= <thomas.weissschuh@...utronix.de>

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>
Acked-by: Nam Cao <namcao@...utronix.de>
Link: https://lore.kernel.org/r/20251014-rv-lockdep-v1-3-0b9e51919ea8@linutronix.de
Signed-off-by: Gabriele Monaco <gmonaco@...hat.com>
---
 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 8c02426bc3bd..d9d335ae9bad 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