linux-kernel - [PATCH] kernel/trace: Stop and wait for kthread on preempt irq module unload

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Message-Id: <20200424223630.224895-1-joel@joelfernandes.org>
Date:   Fri, 24 Apr 2020 18:36:30 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Xiao Yang <yangx.jy@...fujitsu.com>,
        Ingo Molnar <mingo@...hat.com>
Subject: [PATCH] kernel/trace: Stop and wait for kthread on preempt irq module unload

Kthread running the test needs to be stopped or it can continue
executing code unloaded by module causing a crash.

Suggested-by: Steven Rostedt <rostedt@...dmis.org>
Reported-by: Xiao Yang <yangx.jy@...fujitsu.com>
Link: http://lore.kernel.org/r/5EA2B0C8.2080706@cn.fujitsu.com
Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 kernel/trace/preemptirq_delay_test.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c
index 31c0fad4cb9e1..1c28ca20e30b6 100644
--- a/kernel/trace/preemptirq_delay_test.c
+++ b/kernel/trace/preemptirq_delay_test.c
@@ -145,10 +145,10 @@ static struct attribute_group attr_group = {
 };
 
 static struct kobject *preemptirq_delay_kobj;
+static struct task_struct *test_task;
 
 static int __init preemptirq_delay_init(void)
 {
-	struct task_struct *test_task;
 	int retval;
 
 	test_task = preemptirq_start_test();
@@ -171,6 +171,9 @@ static int __init preemptirq_delay_init(void)
 static void __exit preemptirq_delay_exit(void)
 {
 	kobject_put(preemptirq_delay_kobj);
+
+	if (test_task)
+		kthread_stop(test_task);
 }
 
 module_init(preemptirq_delay_init)
-- 
2.26.2.303.gf8c07b1a785-goog