From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264740AbTFQOXs (ORCPT ); Tue, 17 Jun 2003 10:23:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264738AbTFQOXr (ORCPT ); Tue, 17 Jun 2003 10:23:47 -0400 Received: from pub237.cambridge.redhat.com ([213.86.99.237]:13050 "EHLO warthog.warthog") by vger.kernel.org with ESMTP id S264751AbTFQOWw (ORCPT ); Tue, 17 Jun 2003 10:22:52 -0400 From: David Howells To: Linus Torvalds cc: Kernel Mailing List Subject: [PATCH] disentangle printk's whilst oopsing on SMP User-Agent: EMH/1.14.1 SEMI/1.14.4 (Hosorogi) FLIM/1.14.4 (=?ISO-8859-4?Q?Kashiharajing=FE-mae?=) APEL/10.4 Emacs/21.2 (i386-redhat-linux-gnu) MULE/5.0 (SAKAKI) MIME-Version: 1.0 (generated by SEMI 1.14.4 - "Hosorogi") Content-Type: text/plain; charset=US-ASCII Date: Tue, 17 Jun 2003 15:36:43 +0100 Message-ID: <6452.1055860603@warthog.warthog> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi Linus, The attached patch stops printk's issued on different processors from becoming char-by-char interleaved whilst one of them is oopsing. David diff -uNr linux-2.5.72/kernel/printk.c linux-2.5.72-auto/kernel/printk.c --- linux-2.5.72/kernel/printk.c 2003-06-17 15:01:58.000000000 +0100 +++ linux-2.5.72-auto/kernel/printk.c 2003-06-17 15:06:31.000000000 +0100 @@ -373,6 +373,9 @@ logged_chars++; } +/* cpu currently holding logbuf_lock */ +static volatile int printk_cpu = -1; + /* * This is printk. It can be called from any context. We want it to work. * @@ -395,8 +398,9 @@ static char printk_buf[1024]; static int log_level_unknown = 1; - if (oops_in_progress) { - /* If a crash is occurring, make sure we can't deadlock */ + if (oops_in_progress && printk_cpu==smp_processor_id()) { + /* If a crash is occurring during printk() on this CPU, + * make sure we can't deadlock */ spin_lock_init(&logbuf_lock); /* And make sure that we print immediately */ init_MUTEX(&console_sem); @@ -404,6 +408,7 @@ /* This stops the holder of console_sem just where we want him */ spin_lock_irqsave(&logbuf_lock, flags); + printk_cpu = smp_processor_id(); /* Emit the output into the temporary buffer */ va_start(args, fmt);