Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932068AbWIOEmP (ORCPT ); Fri, 15 Sep 2006 00:42:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932069AbWIOEmP (ORCPT ); Fri, 15 Sep 2006 00:42:15 -0400 Received: from smtp.osdl.org ([65.172.181.4]:46310 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S932068AbWIOEmO (ORCPT ); Fri, 15 Sep 2006 00:42:14 -0400 Date: Thu, 14 Sep 2006 21:42:10 -0700 From: Andrew Morton To: Aristeu Sergio Rozanski Filho Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH -mm] 8250: remove not needed NMI watchdog tickle in serial8250_console_write() Message-Id: <20060914214210.9128e032.akpm@osdl.org> In-Reply-To: <20060913205203.GC4787@cathedrallabs.org> References: <20060913205203.GC4787@cathedrallabs.org> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1870 Lines: 42 On Wed, 13 Sep 2006 17:52:03 -0300 Aristeu Sergio Rozanski Filho wrote: > When touch_nmi_watchdog() was added to inside the wait loop in > wait_for_xmitr()[1], where the long delays come from, a unneeded > touch_nmi_watchdog() call was left in the beginning of > serial8250_console_write() (introduced in > 78512ece148992a5c00c63fbf4404f3cde635016) and this patch reverts it. > > [1] http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.18-rc6/2.6.18-rc6-mm2/broken-out/tickle-nmi-watchdog-on-serial-output.patch > http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.18-rc6/2.6.18-rc6-mm2/broken-out/tickle-nmi-watchdog-on-serial-output-fix.patch > [2] http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=78512ece148992a5c00c63fbf4404f3cde635016;hp=0ad775dbba12de3b7d25f586efe81ad995ca75a7 > > Signed-off-by: Aristeu S. Rozanski F. > > --- mm.orig/drivers/serial/8250.c 2006-09-13 17:26:53.000000000 -0300 > +++ mm/drivers/serial/8250.c 2006-09-13 17:27:14.000000000 -0300 > @@ -2263,8 +2263,6 @@ > unsigned int ier; > int locked = 1; > > - touch_nmi_watchdog(); > - > local_irq_save(flags); > if (up->port.sysrq) { > /* serial8250_handle_port() already took the lock */ I disagree. If characters are flowing out at a rate which consistently exceeds one-per-ten-milliseconds, the touch_nmi_watchdog() in wait_for_xmitr() will never be called. Consequently a large interrupt-time write to the serial port (ie: sysrq-T with serial-console enabled) will cause the NMI watchdog to trigger. No? - 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/