From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id E8DD88D003A for ; Mon, 14 Mar 2011 16:40:39 -0400 (EDT) Date: Mon, 14 Mar 2011 21:31:52 +0100 From: Oleg Nesterov Subject: Re: [PATCH 1/3 for 2.6.38] oom: oom_kill_process: don't set TIF_MEMDIE if !p->mm Message-ID: <20110314203152.GA25080@redhat.com> References: <20110309151946.dea51cde.akpm@linux-foundation.org> <20110312123413.GA18351@redhat.com> <20110312134341.GA27275@redhat.com> <20110313212726.GA24530@redhat.com> <20110314190419.GA21845@redhat.com> <20110314190446.GB21845@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: Hugh Dickins , Andrew Morton , KOSAKI Motohiro , KAMEZAWA Hiroyuki , Andrey Vagin , David Rientjes , Frantisek Hrbata , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 03/14, Linus Torvalds wrote: > > On Mon, Mar 14, 2011 at 12:04 PM, Oleg Nesterov wrote: > > oom_kill_process() simply sets TIF_MEMDIE and returns if PF_EXITING. > > This is very wrong by many reasons. In particular, this thread can > > be the dead group leader. Check p->mm != NULL. > > Explain more, please. Maybe I'm missing some context because I wasn't > cc'd on the original thread, but PF_EXITING gets set by exit_signal(), > and exit_mm() is called almost immediately afterwards which will set > p->mm to NULL. > > So afaik, this will basically just remove the whole point of the code > entirely - so why not remove it then? I am afraid I am going to lie... But iirc I tried to remove this code before. Can't find the previous discussion, probably I am wrong. Anyway. I never understood why do we have this special case. > The combination of testing PF_EXITING and p->mm just doesn't seem to > make any sense. To me, it doesn't make too much sense even if we do not check ->mm. But. I _think_ the intent was to wait until this "exiting" process does exit_mm() and frees the memory. This is like the "the process of releasing memory " code in select_bad_process(). Once again, this is only my speculation. In any case, this patch doesn't pretend to be the right fix. Oleg. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org