Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751555AbVJMKNy (ORCPT ); Thu, 13 Oct 2005 06:13:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751549AbVJMKNy (ORCPT ); Thu, 13 Oct 2005 06:13:54 -0400 Received: from smtp.osdl.org ([65.172.181.4]:9407 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751499AbVJMKNx (ORCPT ); Thu, 13 Oct 2005 06:13:53 -0400 Date: Thu, 13 Oct 2005 03:13:47 -0700 From: Chris Wright To: Jamie Lokier Cc: Janak Desai , chrisw@osdl.org, viro@ZenIV.linux.org.uk, nickpiggin@yahoo.com.au, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, akpm@osdl.org Subject: Re: [PATCH] New System call unshare (try 2) Message-ID: <20051013101347.GN5856@shell0.pdx.osdl.net> References: <20051012171914.GA8622@mail.shareable.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20051012171914.GA8622@mail.shareable.org> User-Agent: Mutt/1.5.6i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1598 Lines: 43 * Jamie Lokier (jamie@shareable.org) wrote: > Janak Desai wrote: > > Don't allow sighand unsharing if not unsharing vm > > Why not? It's permitted to clone with unshared sighand and shared vm, > and it's useful too. I think that one's just backwards. Although I do question how useful it is to unshare sighand. Sharing vm is pretty intimate ;-) > It's the combination shared sighand + unshared vm which is not > allowed by clone - so I think that's what you should refuse. > > > Don't allow vm unsharing if task cloned with CLONE_THREAD > > It would be better to do what clone does, and say "don't allow sighand > unsharing if task cloned with CLONE_THREAD". This is because > CLONE_THREAD tasks must have shared signals. Yes, I agree. > In combination with the rule above for sighand (my rule, not yours), > that implies "don't allow vm unsharing.." as a consequence. > > > Don't allow vm unsharing if the task is performing async io > > Why not? > > Async ios are tied to an mm (see lookup_ioctx in fs/aio.c), which may > be shared among tasks. I see no reason why the async ios can't > continue and be waited in on in other tasks that may be using the old mm. My concern was the case where there are no other tasks. But I don't think that's an issue other than having the aio effect of setting up aio then exiting. thanks, -chris - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/