linux-kernel - Re: [PATCH] kernel/hung_task.c: add error info when failed to start khungtaskd

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Date:   Fri, 22 Oct 2021 19:12:26 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Weitao Hou <houweitao@...iglobal.com>
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        lukas.bulwahn@...il.com, sfr@...b.auug.org.au,
        linux@...musvillemoes.dk, peterz@...radead.org,
        andriy.shevchenko@...ux.intel.com
Subject: Re: [PATCH] kernel/hung_task.c: add error info when failed to start
 khungtaskd

Hello.

On 2021/10/22 17:47, Weitao Hou wrote:
> we need add necessary error info when core thread started failed

This message is little useful. If kthread_run() from built-in modules' __init
functions is failing (due to e.g. out of memory), the system is already unusable.

> 
> Signed-off-by: Weitao Hou <houweitao@...iglobal.com>
> ---
>  kernel/hung_task.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/kernel/hung_task.c b/kernel/hung_task.c
> index 8cc07e7f29aa..8a95997a693e 100644
> --- a/kernel/hung_task.c
> +++ b/kernel/hung_task.c
> @@ -354,6 +354,10 @@ static int __init hung_task_init(void)
>  	pm_notifier(hungtask_pm_notify, 0);
>  
>  	watchdog_task = kthread_run(watchdog, NULL, "khungtaskd");
> +	if (IS_ERR(watchdog_task)) {
> +		pr_err("Failed to start khungtaskd\n");
> +		watchdog_task = NULL;
> +	}
>  
>  	return 0;
>  }
>