From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933502AbXDFRQ6 (ORCPT ); Fri, 6 Apr 2007 13:16:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933504AbXDFRQ6 (ORCPT ); Fri, 6 Apr 2007 13:16:58 -0400 Received: from smtp.osdl.org ([65.172.181.24]:56712 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933510AbXDFRQ4 (ORCPT ); Fri, 6 Apr 2007 13:16:56 -0400 Date: Fri, 6 Apr 2007 10:16:27 -0700 (PDT) From: Linus Torvalds To: Oleg Nesterov cc: "Eric W. Biederman" , Robin Holt , Chris Snook , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: init's children list is long and slows reaping children. In-Reply-To: <20070406154750.GA541@tv-sign.ru> Message-ID: References: <20070406084250.GA179@tv-sign.ru> <20070406094413.GA673@tv-sign.ru> <20070406154750.GA541@tv-sign.ru> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 6 Apr 2007, Oleg Nesterov wrote: > > Oops. I misread stop_machine(), it does kernel_thread(), not kthread_create(). > So "stopmachine" threads are all re-parented to init when the caller exits. > I think it makes sense to set ->exit_state = -1 in stopmachine(), regadless > of any other changes. I agree that "->exit_state = -1" makes sense, but I disagree in that I don't think it *matters*. Most of the problematic kernel threads are long-running (as in "never exit"). Things like eventd, khelper, migration-threads etc will have init as their parent and never actually exit, so their ->exit_state doesn't matter. What matters is that they are on the children list, so when you have 1024 CPU's, and init has many thousand of these per-cpu threads as its children, then the *user* threads (that do exit) will cause problems! I'd almost prefer to just not add kernel threads to any parent process list *at*all*. Linus