linux-kernel - Re: [PATCH, RFC] Remove fasync() BKL usage, take 3325

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Message-ID: <20090122160935.GI15750@one.firstfloor.org>
Date:	Thu, 22 Jan 2009 17:09:35 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jonathan Corbet <corbet@....net>, linux-kernel@...r.kernel.org,
	andi@...stfloor.org, viro@...IV.linux.org.uk, oleg@...hat.com,
	linux-api@...r.kernel.org, alan@...rguk.ukuu.org.uk
Subject: Re: [PATCH, RFC] Remove fasync() BKL usage, take 3325

> OK, replacing a lock_kernel() with a spin_lock(&global_lock) is pretty
> straightforwad.  But it's really really sad.  It basically leaves a great
> big FIXME in there.  It'd be better to fix it.

Also it might be that it's even worse than the BKL.

> 
> We don't have a handy lock in struct file which could be borrowed.
> 
> - We could add one
> 
> - We could borrow file->f_path.dentry->d_inode->i_lock
> 
> - We could convert that field to long and use bitops (sounds nice?)

It would still require a bitlock because some state in the low
level fasync needs to be protected.

Oleg has a proposal to do this using a flag bit which seemed
reasonable to me.

-Andi

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