From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC] page fault retry with NOPAGE_RETRY From: Benjamin Herrenschmidt In-Reply-To: References: <1158274508.14473.88.camel@localhost.localdomain> <20060915001151.75f9a71b.akpm@osdl.org> <20060915003529.8a59c542.akpm@osdl.org> Content-Type: text/plain Date: Sat, 16 Sep 2006 11:03:00 +1000 Message-Id: <1158368580.14473.207.camel@localhost.localdomain> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Hugh Dickins Cc: Andrew Morton , linux-mm@kvack.org, Linux Kernel list , Linus Torvalds , Mike Waychison List-ID: On Fri, 2006-09-15 at 14:30 +0100, Hugh Dickins wrote: > On Fri, 15 Sep 2006, Andrew Morton wrote: > > > > This assumes that no other heavyweight process will try to modify this > > single-threaded process's mm. I don't _think_ that happens anywhere, does > > it? access_process_vm() is the only case I can think of, > > "Modify" in the sense of fault into. > Yes, access_process_vm() is all I can think of too. > > > and it does down_read(other process's mmap_sem). > > If there were anything else, it'd have to do so too (if not down_write). > > I too like NOPAGE_RETRY: as you've both observed, it can help to solve > several different problems. Yes, I don't need any of the safeguards that Andrew mentioned in my case though. I want to return all the way to userland because I want signals to be handled (which might also be a good thing in your case in fact, so that a process being starved by that new mecanism can still be interrupted). I would ask that if you decide that the more complex approach is not 2.6.19 material, that the simple addition of NOPAGE_RETRY as I've defined could be included in a first step so I can solve my problem (and possibly other drivers wanting to do funky things with no_page() and still take signals), and the google patch be rebased on top of that for additional simmering :) Cheers, Ben. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org