Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262689AbVENG6C (ORCPT ); Sat, 14 May 2005 02:58:02 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262690AbVENG6C (ORCPT ); Sat, 14 May 2005 02:58:02 -0400 Received: from mx1.redhat.com ([66.187.233.31]:52711 "EHLO mx1.redhat.com") by vger.kernel.org with ESMTP id S262689AbVENG55 (ORCPT ); Sat, 14 May 2005 02:57:57 -0400 Date: Sat, 14 May 2005 02:57:53 -0400 From: Dave Jones To: Andrew Morton Cc: linux-kernel@vger.kernel.org Subject: Re: tickle nmi watchdog whilst doing serial writes. Message-ID: <20050514065753.GA28213@redhat.com> Mail-Followup-To: Dave Jones , Andrew Morton , linux-kernel@vger.kernel.org References: <20050513184806.GA24166@redhat.com> <20050513234331.0d097cb1.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050513234331.0d097cb1.akpm@osdl.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2245 Lines: 74 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. 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; + } + } } } Signed-off-by: Dave Jones totally uncompiled & untested. I'm not even sure about that magic '100'. I'll let someone less sleep-deprived than myself choose a better number. Dave - 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/