From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263020AbVHENuX (ORCPT ); Fri, 5 Aug 2005 09:50:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263024AbVHENuX (ORCPT ); Fri, 5 Aug 2005 09:50:23 -0400 Received: from vana.vc.cvut.cz ([147.32.240.58]:64936 "EHLO vana.vc.cvut.cz") by vger.kernel.org with ESMTP id S263020AbVHENuL (ORCPT ); Fri, 5 Aug 2005 09:50:11 -0400 Date: Fri, 5 Aug 2005 15:50:07 +0200 From: Petr Vandrovec To: torvalds@osdl.org Cc: akpm@osdl.org, linux-kernel@vger.kernel.org Subject: [PATCH 2.6.13-rc5-gitNOW] msleep() cannot be used from interrupt Message-ID: <20050805135007.GA6985@vana.vc.cvut.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hello Linus, can you apply patch below? Since beginning of July my Opteron box was randomly crashing and being rebooted by hardware watchdog. Today it finally did it in front of me, and this patch will hopefully fix it. Problem is that at the end of June (28th, commit 47f176fdaf8924bc83fddcf9658f2fd3ef60d573, [PATCH] Using msleep() instead of HZ) rtc_get_rtc_time was converted to use msleep() instead of busy waiting. But rtc_get_rtc_time is used by hpet_rtc_interrupt, and scheduling is not allowed during interrupt. So I'm reverting this part of original change, replacing msleep() back with busy loop. Original old code was busy waiting for 20ms, while on my hardware in the worst case update-in-progress bit was asserted for at most 363 passes through loop (on 2GHz dual Opteron), much less than even one jiffie, not even talking about 20ms. So I changed code to just wait only as long as necessary. Otherwise when RTC was set to generate 8192Hz timer, it stopped doing anything for 20ms (160 pulses were skipped!) from time to time, and this is rather suboptimal as far as I can tell. Thanks, Petr Vandrovec Signed-off-by: Petr Vandrovec diff -urdN linux/drivers/char/rtc.c linux/drivers/char/rtc.c --- linux/drivers/char/rtc.c 2005-08-05 12:43:54.000000000 +0000 +++ linux/drivers/char/rtc.c 2005-08-05 13:26:48.000000000 +0000 @@ -1209,6 +1209,7 @@ void rtc_get_rtc_time(struct rtc_time *rtc_tm) { + unsigned long uip_watchdog = jiffies; unsigned char ctrl; #ifdef CONFIG_MACH_DECSTATION unsigned int real_year; @@ -1224,8 +1225,10 @@ * Once the read clears, read the RTC time (again via ioctl). Easy. */ - if (rtc_is_updating() != 0) - msleep(20); + while (rtc_is_updating() != 0 && jiffies - uip_watchdog < 2*HZ/100) { + barrier(); + cpu_relax(); + } /* * Only the values that we read from the RTC are set. We leave