Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262692AbVENHIj (ORCPT ); Sat, 14 May 2005 03:08:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262694AbVENHIj (ORCPT ); Sat, 14 May 2005 03:08:39 -0400 Received: from fire.osdl.org ([65.172.181.4]:12218 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S262692AbVENHIN (ORCPT ); Sat, 14 May 2005 03:08:13 -0400 Date: Sat, 14 May 2005 00:07:23 -0700 From: Andrew Morton To: Dave Jones Cc: linux-kernel@vger.kernel.org Subject: Re: tickle nmi watchdog whilst doing serial writes. Message-Id: <20050514000723.73bd6e5a.akpm@osdl.org> In-Reply-To: <20050514065753.GA28213@redhat.com> References: <20050513184806.GA24166@redhat.com> <20050513234331.0d097cb1.akpm@osdl.org> <20050514065753.GA28213@redhat.com> X-Mailer: Sylpheed version 1.0.0 (GTK+ 1.2.10; i386-vine-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: 3076 Lines: 96 Dave Jones wrote: > > On Fri, May 13, 2005 at 11:43:31PM -0700, Andrew Morton wrote: > > Dave Jones wrote: > > > > > > This was fun. I inserted a music CD with some obnoxious copy-protection > > > on it into the drive, and lots of SCSI errors went zipping over to > > > the serial console. Unfortunatly, the box was also compiling a kernel, > > > playing oggs, and doing a number of other things at the same time, > > > so this happened.. > > > > > > NMI Watchdog detected LOCKUP on CPU2CPU 2 > > > > OK.. But calling touch_nmi_watchdog() at 1MHz seems a bit excessive, and > > might perturb the finely-tuned timing in there. > > > > How's about this? > > Umm.. Despite it being past my bedtime, I'm pretty sure I'm > missing something here... > > > + while (!(serial_in(up, UART_MSR) & UART_MSR_CTS) && --tmout) > > udelay(1); > > I don't see how this is any better than the current code. > We're doing 1000000 udelays. Whilst we're doing that, > the nmi watchdog goes bonkers. > > > + if (tmout < 1000000) > > + touch_nmi_watchdog(); > > So by the time we do this, its already triggered. But the NMI watchdog won't expire after one second - normally it's set to fixe seconds. > How about.. > > --- linux-2.6.11/drivers/serial/8250.c~ 2005-05-14 02:49:02.000000000 -0400 > +++ linux-2.6.11/drivers/serial/8250.c 2005-05-14 02:54:30.000000000 -0400 > @@ -40,6 +40,7 @@ > #include > #include > #include > +#include > > #include > #include > @@ -2099,8 +2100,15 @@ static inline void wait_for_xmitr(struct > if (up->port.flags & UPF_CONS_FLOW) { > tmout = 1000000; > while (--tmout && > - ((serial_in(up, UART_MSR) & UART_MSR_CTS) == 0)) > + ((serial_in(up, UART_MSR) & UART_MSR_CTS) == 0)) { > + int cnt=0; > udelay(1); > + cnt++; > + if (cnt==100) { > + touch_nmi_watchdog(); > + cnt=0; > + } > + } spose so. --- 25/drivers/serial/8250.c~tickle-nmi-watchdog-whilst-doing-serial-writes 2005-05-14 00:03:09.000000000 -0700 +++ 25-akpm/drivers/serial/8250.c 2005-05-14 00:06:53.000000000 -0700 @@ -40,6 +40,7 @@ #include #include #include +#include #include #include @@ -2098,9 +2099,11 @@ static inline void wait_for_xmitr(struct /* Wait up to 1s for flow control if necessary */ if (up->port.flags & UPF_CONS_FLOW) { tmout = 1000000; - while (--tmout && - ((serial_in(up, UART_MSR) & UART_MSR_CTS) == 0)) + while (!(serial_in(up, UART_MSR) & UART_MSR_CTS) && --tmout) { udelay(1); + if ((tmout % 1000) == 0) + touch_nmi_watchdog(); + } } } _ - 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/