linux-kernel - Re: [PATCH] cgroup: make cgrp->event_list

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Message-ID: <CAOS58YNJd557hGDMGqavp8eq+B9x5WExCcpW+CwZ8dUainjUUw@mail.gmail.com>
Date:	Tue, 5 Mar 2013 23:21:03 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: Re: [PATCH] cgroup: make cgrp->event_list_lock irqsafe

Hello, Li.

On Tue, Mar 5, 2013 at 11:15 PM, Li Zefan <lizefan@...wei.com> wrote:
> wqh->lock is used through out fs/eventfd.c. I don't know if currently there's
> any kernel user using eventfd APIs in an irq handler, but at least that should
> be allowed.
>
> wake_up() is also allowed to be called from irq handler?

Yeah, well, we don't consider everything which uses wake_up() to be
irq-safe. I'm not necessarily against making the lock irq-safe but at
least the commit message is misleading as currently posted. I'd
suggest looking at eventfd and see whether the wakeup could actually
happen from irq context. If not, I don't know, I don't think it
matters either way. It's not like it's a difficult one to detect with
lockdep.

-- 
tejun
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