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Date:   Sat, 05 Jan 2019 14:10:21 -0800 (PST)
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        daniel@iogearbox.net, ast@kernel.org, mcgrof@kernel.org
Subject: Re: [PATCH net 1/4] umh: add exit routine for UMH process
From:   David Miller <davem@davemloft.net>
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From: Taehee Yoo <ap420073@gmail.com>
Date: Mon, 31 Dec 2018 01:31:43 +0900

> +void exit_umh(struct task_struct *tsk)
> +{
> +	struct umh_info *info;
> +	pid_t pid = tsk->pid;
> +
> +	mutex_lock(&umh_list_lock);
> +	list_for_each_entry(info, &umh_list, list) {

So this is probably too expensive of a cost for every process exit.
The problem is that the cost will be taken even if the process is
not a UMH.

I've taken my time to respond in hopes that I could come up with a
good alternative to suggest, but so far I don't have any better ideas.

I'll keep thinking about this some more, please let me know if you
have any ideas.