This is a note to let you know that I've just added the patch titled
tracing: Wait for preempt irq delay thread to finish
to the 5.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-wait-for-preempt-irq-delay-thread-to-finish.patch
and it can be found in the queue-5.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From d16a8c31077e75ecb9427fbfea59b74eed00f698 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Date: Wed, 6 May 2020 10:20:10 -0400
Subject: tracing: Wait for preempt irq delay thread to finish
From: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
commit d16a8c31077e75ecb9427fbfea59b74eed00f698 upstream.
Running on a slower machine, it is possible that the preempt delay kernel
thread may still be executing if the module was immediately removed after
added, and this can cause the kernel to crash as the kernel thread might be
executing after its code has been removed.
There's no reason that the caller of the code shouldn't just wait for the
delay thread to finish, as the thread can also be created by a trigger in
the sysfs code, which also has the same issues.
Link: http://lore.kernel.org/r/5EA2B0C8.2080706@xxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 793937236d1ee ("lib: Add module for testing preemptoff/irqsoff latency tracers")
Reported-by: Xiao Yang <yangx.jy@xxxxxxxxxxxxxx>
Reviewed-by: Xiao Yang <yangx.jy@xxxxxxxxxxxxxx>
Reviewed-by: Joel Fernandes <joel@xxxxxxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/preemptirq_delay_test.c | 30 ++++++++++++++++++++++++------
1 file changed, 24 insertions(+), 6 deletions(-)
--- a/kernel/trace/preemptirq_delay_test.c
+++ b/kernel/trace/preemptirq_delay_test.c
@@ -113,22 +113,42 @@ static int preemptirq_delay_run(void *da
for (i = 0; i < s; i++)
(testfuncs[i])(i);
+
+ set_current_state(TASK_INTERRUPTIBLE);
+ while (!kthread_should_stop()) {
+ schedule();
+ set_current_state(TASK_INTERRUPTIBLE);
+ }
+
+ __set_current_state(TASK_RUNNING);
+
return 0;
}
-static struct task_struct *preemptirq_start_test(void)
+static int preemptirq_run_test(void)
{
+ struct task_struct *task;
+
char task_name[50];
snprintf(task_name, sizeof(task_name), "%s_test", test_mode);
- return kthread_run(preemptirq_delay_run, NULL, task_name);
+ task = kthread_run(preemptirq_delay_run, NULL, task_name);
+ if (IS_ERR(task))
+ return PTR_ERR(task);
+ if (task)
+ kthread_stop(task);
+ return 0;
}
static ssize_t trigger_store(struct kobject *kobj, struct kobj_attribute *attr,
const char *buf, size_t count)
{
- preemptirq_start_test();
+ ssize_t ret;
+
+ ret = preemptirq_run_test();
+ if (ret)
+ return ret;
return count;
}
@@ -148,11 +168,9 @@ static struct kobject *preemptirq_delay_
static int __init preemptirq_delay_init(void)
{
- struct task_struct *test_task;
int retval;
- test_task = preemptirq_start_test();
- retval = PTR_ERR_OR_ZERO(test_task);
+ retval = preemptirq_run_test();
if (retval != 0)
return retval;
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-5.6/tracing-wait-for-preempt-irq-delay-thread-to-finish.patch
queue-5.6/tracing-boottime-fix-kprobe-event-api-usage.patch
queue-5.6/tracing-kprobes-reject-new-event-if-loc-is-null.patch
queue-5.6/tracing-kprobes-fix-a-double-initialization-typo.patch
queue-5.6/tracing-add-a-vmalloc_sync_mappings-for-safe-measure.patch
