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

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Message-ID: <5EA96AE8.6000707@cn.fujitsu.com>
Date:   Wed, 29 Apr 2020 19:54:16 +0800
From:   Xiao Yang <yangx.jy@...fujitsu.com>
To:     Steven Rostedt <rostedt@...dmis.org>
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 2020/4/28 22:45, Steven Rostedt wrote:
> 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;
>>    }
>>
Hi Steven,

Thanks for your patch.

I also used the following steps to do test and didn't get any 
warning/panic after applying your patch.
---------------------------------
for i in $(seq 1 100); do modprobe preemptirq_delay_test test_mode=irq 
delay=500000; rmmod preemptirq_delay_test; done
for i in $(seq 1 100); do modprobe preemptirq_delay_test 
test_mode=preempt delay=500000; rmmod preemptirq_delay_test; done
---------------------------------

But I am not sure which fix(from you and Joel) is better.

Thanks,
Xiao Yang