From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Morton Subject: Re: [PATCH, RFC] Remove fasync() BKL usage, take 3325 Date: Thu, 22 Jan 2009 21:31:05 -0800 Message-ID: <20090122213105.74142908.akpm@linux-foundation.org> References: <20090115153211.663df310@bike.lwn.net> <20090122065104.2787df2d.akpm@linux-foundation.org> <20090122221500.4c62aa54@tpl> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20090122221500.4c62aa54@tpl> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Jonathan Corbet Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org, viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org, oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, alan-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org List-Id: linux-api@vger.kernel.org > On Thu, 22 Jan 2009 22:15:00 -0700 Jonathan Corbet wrote: > On Thu, 22 Jan 2009 06:51:04 -0800 > Andrew Morton wrote: > > > 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. > > > > We don't have a handy lock in struct file which could be borrowed. > > Yeah, I noticed that too. > > > - We could add one > > The problem there is that this bloats struct file, and that seemed like > something worth avoiding. Not a big deal, really. There's one of these for each presently-open file. It's not like dentries and inodes, which we cache after userspace has closed off the file handles. > It could easily be done, but I don't know > why we would before knowing that the global spinlock is a problem. > > But... it's *already* protected by a global spinlock (the BKL) which is > (still) more widely used. > > > - We could borrow file->f_path.dentry->d_inode->i_lock > > I didn't think of that one. Using a lock which is three indirections > away seems a little obscure; again, I guess we could do that if the > global spinlock actually turns out to be a problem. > > > - We could convert that field to long and use bitops (sounds nice?) > > I did think of that one. Reasons not to include growing struct file > and the fact that there are places which set more than one flag at > once. So we'd replace assignments with loops - and we still don't > solve the fasync() problem. > I don't know what "the fasync() problem" is? -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html