linux-kernel - Re: [PATCH] task_work: add a scheduling point in task_work

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Message-ID: <20120822053847.GM23464@ZenIV.linux.org.uk>
Date:	Wed, 22 Aug 2012 06:38:47 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Michael Wang <wangyun@...ux.vnet.ibm.com>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	". James Morris" <jmorris@...ei.org>,
	linux-security-module@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>
Subject: Re: [PATCH] task_work: add a scheduling point in task_work_run()

On Wed, Aug 22, 2012 at 01:27:21PM +0800, Michael Wang wrote:

> And can we make sure that it is safe to sleep(schedule) at this point?
> It may need some totally testing to cover all the situation...

task_work callback can bloody well block, so yes, it is safe.  Hell,
we are doing final close from that; that can lead to any amount of
IO, up to and including on-disk file freeing and, in case of vfsmount
kept alive by an opened file after we'd done umount -l, actual final
unmount of a filesystem.  That can more than just block, that can block
for a long time if that's a network filesystem...
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