Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964787AbWH1KpE (ORCPT ); Mon, 28 Aug 2006 06:45:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964788AbWH1KpD (ORCPT ); Mon, 28 Aug 2006 06:45:03 -0400 Received: from cantor.suse.de ([195.135.220.2]:55523 "EHLO mx1.suse.de") by vger.kernel.org with ESMTP id S964787AbWH1KpB (ORCPT ); Mon, 28 Aug 2006 06:45:01 -0400 Date: Mon, 28 Aug 2006 12:44:59 +0200 From: Nick Piggin To: Oleg Nesterov Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH -mm] select_bad_process: cleanup 'releasing' check Message-ID: <20060828104459.GA14010@wotan.suse.de> References: <20060827182538.GA1779@oleg> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060827182538.GA1779@oleg> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2303 Lines: 63 On Sun, Aug 27, 2006 at 10:25:38PM +0400, Oleg Nesterov wrote: > On top of "select_bad_process: kill a bogus PF_DEAD/TASK_DEAD check" > > No logic changes, but imho easier to read. > > Signed-off-by: Oleg Nesterov > > --- 2.6.18-rc4/mm/oom_kill.c~ 2006-08-27 20:56:23.000000000 +0400 > +++ 2.6.18-rc4/mm/oom_kill.c 2006-08-27 21:58:32.000000000 +0400 > @@ -205,7 +205,6 @@ static struct task_struct *select_bad_pr > do_posix_clock_monotonic_gettime(&uptime); > do_each_thread(g, p) { > unsigned long points; > - int releasing; > > /* > * skip kernel threads and tasks which have already released > @@ -227,16 +226,15 @@ static struct task_struct *select_bad_pr > * the process of exiting and releasing its resources. > * Otherwise we could get an OOM deadlock. > */ > - releasing = test_tsk_thread_flag(p, TIF_MEMDIE) || > - p->flags & PF_EXITING; > - if (releasing) { > - if (p->flags & PF_EXITING && p == current) { > - chosen = p; > - *ppoints = ULONG_MAX; > - break; > - } > - return ERR_PTR(-1UL); > - } > + if ((p->flags & PF_EXITING) && p == current) { > + chosen = p; > + *ppoints = ULONG_MAX; > + break; > + } > + if ((p->flags & PF_EXITING) || > + test_tsk_thread_flag(p, TIF_MEMDIE)) > + return ERR_PTR(-1UL); > + Hmm, actually I think I spot a bug in the original logic: we don't want to have more than 1 task with TIF_MEMDIE at once, becaues that gives it access to memory reserves (but I saw it first in the new formulation, so maybe that does suggest it is more readable ;) What I think should be done is the check for TIF_MEMDIE (and return -1) first, and then the PF_EXITING test. At which point, if current is found to be exiting, it should be chosen but not break... that way a subsequent MEMDIE or EXITING task has the chance to trigger the -1 return. Anyway, if you don't want to do all that, I will when my hand gets better. Otherwise the 3 patches you sent look good, they could all have an Acked-by: Nick Piggin Thanks, Nick - 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/