From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 22 May 2002 19:32:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 22 May 2002 19:32:51 -0400 Received: from mail.ocs.com.au ([203.34.97.2]:48393 "HELO mail.ocs.com.au") by vger.kernel.org with SMTP id ; Wed, 22 May 2002 19:32:49 -0400 X-Mailer: exmh version 2.2 06/23/2000 with nmh-1.0.4 From: Keith Owens To: Eric Weigle Cc: "Linux kernel mailing list (lkml)" Subject: Re: Safety of -j N when building kernels? In-Reply-To: Your message of "Wed, 22 May 2002 10:53:20 CST." <20020522165320.GC18059@lanl.gov> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Thu, 23 May 2002 09:32:38 +1000 Message-ID: <344.1022110358@ocs3.intra.ocs.com.au> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 22 May 2002 10:53:20 -0600, Eric Weigle wrote: >So are the kernel's current Makefiles really SMP safe -- can one really >run multiple jobs when building Linux kernels? Any horror stories, or am >I just paranoid? make dep is not parallel safe. On some architectures make -jN dep will generate corrupt data, especially with module symbol versions. You might get away with it. It is not safe on any architecture to make -jN *config dep bzImage modules in one command, you need three separate commands for make -jN *config, make -jN dep and make -jN bzImage modules. The install step must also be a separate command. Building bzImage and modules should be parallel safe, as long as your machine can take the cpu load and has enough file descriptors. Sometimes people do not understand makefiles so the odd driver may not build correctly. aic7xxx around 2.4.19-pre5 was not parallel safe. Of course, in kbuild 2.5, all of this is parallel safe. make -j *config install works fine.