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

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Date:   Tue, 28 Apr 2020 10:45:43 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Xiao Yang <yangx.jy@...fujitsu.com>
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH] kernel/trace: Stop and wait for kthread on preempt irq
 module unload

On Tue, 28 Apr 2020 10:44:09 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 28 Apr 2020 18:19:05 +0800
> Xiao Yang <yangx.jy@...fujitsu.com> wrote:
> 
> > Hi Joel,
> > 
> > Thanks for your quick fix.
> > 
> > Unfortunately, it fixes my original panic but introduces other
> > issues(two wanings and one panic) on my arm64 vm, as below:
> >  
> 
> Does the following on top of Joel's patch fix it?
> 
> -- Steve
> 
> diff --git a/kernel/trace/preemptirq_delay_test.c b/kernel/trace/preemptirq_delay_test.c
> index 1c28ca20e30b..6d9131ae7e8c 100644
> --- a/kernel/trace/preemptirq_delay_test.c
> +++ b/kernel/trace/preemptirq_delay_test.c
> @@ -113,15 +113,27 @@ static int preemptirq_delay_run(void *data)
>  
>  	for (i = 0; i < s; i++)
>  		(testfuncs[i])(i);
> +
> +	while (!kthread_should_stop()) {
> +		schedule();
> +		set_current_state(TASK_INTERRUPTIBLE);
> +	}
> +
> +	__set_current_state(TASK_RUNNING);
> +
>  	return 0;
>  }
>  


The below isn't needed, as the return does check IS_ERR().

-- Steve

>  static struct task_struct *preemptirq_start_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 NULL;
> +	return task;
>  }
>  
>  
>