[PATCH v2] thermal: testing: zone: Flush work items during cleanup

[Rafael J. Wysocki]

From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

To prevent freed module code from being executed during the thermal
testing module unload, make it add a dedicated workqueue for thermal
testing work items and flush it in thermal_testing_exit().

Fixes: f6a034f2df42 ("thermal: Introduce a debugfs-based testing facility")
Link: https://sashiko.dev/#/patchset/20260605185212.2491144-1-sam.moelius%40trailofbits.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
---

This is an update of

https://lore.kernel.org/linux-pm/5107023.GXAFRqVoOG@rafael.j.wysocki/

sent to address Sashiko feedback

https://sashiko.dev/#/patchset/12941879.O9o76ZdvQC%40rafael.j.wysocki

(and the first patch in the series is not really necessary, so it has been
dropped).

Thanks!

---
 drivers/thermal/testing/command.c         |   35 ++++++++++++++++++++++++++----
 drivers/thermal/testing/thermal_testing.h |    8 ++++++
 drivers/thermal/testing/zone.c            |    7 ++----
 3 files changed, 42 insertions(+), 8 deletions(-)

--- a/drivers/thermal/testing/command.c
+++ b/drivers/thermal/testing/command.c
@@ -86,7 +86,9 @@
 
 #include "thermal_testing.h"
 
-struct dentry *d_testing;
+struct workqueue_struct *tt_wq __ro_after_init;
+
+struct dentry *d_testing, *d_command __ro_after_init;
 
 #define TT_COMMAND_SIZE		16
 
@@ -203,17 +205,42 @@ static const struct file_operations tt_c
 
 static int __init thermal_testing_init(void)
 {
+	int error;
+
+	tt_wq = alloc_workqueue("thermal_testing", WQ_UNBOUND, 0);
+	if (!tt_wq)
+		return -ENOMEM;
+
 	d_testing = debugfs_create_dir("thermal-testing", NULL);
-	if (!IS_ERR(d_testing))
-		debugfs_create_file("command", 0200, d_testing, NULL,
-				    &tt_command_fops);
+	if (IS_ERR(d_testing)) {
+		error = PTR_ERR(d_testing);
+		goto destroy_wq;
+	}
+
+	d_command = debugfs_create_file("command", 0200, d_testing, NULL, &tt_command_fops);
+	if (IS_ERR(d_command)) {
+		error = PTR_ERR(d_command);
+		goto remove_d_testing;
+	}
 
 	return 0;
+
+remove_d_testing:
+	debugfs_remove(d_testing);
+destroy_wq:
+	destroy_workqueue(tt_wq);
+	return error;
 }
 module_init(thermal_testing_init);
 
 static void __exit thermal_testing_exit(void)
 {
+	/* First, prevent new commands from being entered. */
+	debugfs_remove(d_command);
+	/* Flush commands in progress (if any). */
+	flush_workqueue(tt_wq);
+	destroy_workqueue(tt_wq);
+	/* Remove the directory structure and clean up. */
 	debugfs_remove(d_testing);
 	tt_zone_cleanup();
 }
--- a/drivers/thermal/testing/thermal_testing.h
+++ b/drivers/thermal/testing/thermal_testing.h
@@ -1,4 +1,12 @@
 /* SPDX-License-Identifier: GPL-2.0 */
+#include <linux/workqueue.h>
+
+extern struct workqueue_struct *tt_wq;
+
+static inline void tt_queue_work(struct work_struct *work)
+{
+	queue_work(tt_wq, work);
+}
 
 extern struct dentry *d_testing;
 
--- a/drivers/thermal/testing/zone.c
+++ b/drivers/thermal/testing/zone.c
@@ -13,7 +13,6 @@
 #include <linux/idr.h>
 #include <linux/list.h>
 #include <linux/thermal.h>
-#include <linux/workqueue.h>
 
 #include "thermal_testing.h"
 
@@ -207,7 +206,7 @@ int tt_add_tz(void)
 
 	INIT_WORK(&tt_work->work, tt_add_tz_work_fn);
 	tt_work->tt_zone = no_free_ptr(tt_zone);
-	schedule_work(&(no_free_ptr(tt_work)->work));
+	tt_queue_work(&(no_free_ptr(tt_work)->work));
 
 	return 0;
 }
@@ -269,7 +268,7 @@ int tt_del_tz(const char *arg)
 
 	INIT_WORK(&tt_work->work, tt_del_tz_work_fn);
 	tt_work->tt_zone = tt_zone;
-	schedule_work(&(no_free_ptr(tt_work)->work));
+	tt_queue_work(&(no_free_ptr(tt_work)->work));
 
 	return 0;
 }
@@ -358,7 +357,7 @@ int tt_zone_add_trip(const char *arg)
 	INIT_WORK(&tt_work->work, tt_zone_add_trip_work_fn);
 	tt_work->tt_zone = no_free_ptr(tt_zone);
 	tt_work->tt_trip = no_free_ptr(tt_trip);
-	schedule_work(&(no_free_ptr(tt_work)->work));
+	tt_queue_work(&(no_free_ptr(tt_work)->work));
 
 	return 0;
 }