linux-kernel - Re: [PATCH v2 1/3] cgroup: fix mount failure in a corner case

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Message-ID: <20140628115743.GB10829@htj.dyndns.org>
Date:	Sat, 28 Jun 2014 07:58:39 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] cgroup: fix mount failure in a corner case

Hello, Li.

On Fri, Jun 27, 2014 at 05:13:12PM +0800, Li Zefan wrote:
> +	for_each_subsys(ss, i) {
> +		if (!(opts.subsys_mask & (1 << i)) ||
> +		    ss->root == &cgrp_dfl_root)
> +			continue;
> +
> +		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
> +			mutex_unlock(&cgroup_mutex);
> +			msleep(10);
> +			ret = restart_syscall();
> +			goto out_free;
> +		}

Why not just put it immediately?  We know that it's not gonna be
destroyed while holding cgroup_mutex.  It may look a bit weird but
this is a pretty special case anyway and deferring put doesn't buy
anything.

Thanks.

-- 
tejun
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