Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 17 Sep 2002 13:13:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 17 Sep 2002 13:13:31 -0400 Received: from smtpout.mac.com ([204.179.120.85]:27614 "EHLO smtpout.mac.com") by vger.kernel.org with ESMTP id ; Tue, 17 Sep 2002 13:13:29 -0400 Date: Tue, 17 Sep 2002 19:18:19 +0200 Subject: Re: Oops in sched.c on PPro SMP Content-Type: text/plain; charset=US-ASCII; format=flowed Mime-Version: 1.0 (Apple Message framework v482) Cc: Alan Cox , linux-kernel@vger.kernel.org, mingo@redhat.com To: Andrea Arcangeli From: Peter Waechtler In-Reply-To: <20020916231303.GF11605@dualathlon.random> Message-Id: <7617860B-CA61-11D6-8873-00039387C942@mac.com> Content-Transfer-Encoding: 7bit X-Mailer: Apple Mail (2.482) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2825 Lines: 71 Am Dienstag den, 17. September 2002, um 01:13, schrieb Andrea Arcangeli: > On Mon, Sep 16, 2002 at 11:16:20PM +0200, Peter Waechtler wrote: >> Am Montag den, 16. September 2002, um 17:44, schrieb Andrea Arcangeli: >> >>> On Mon, Sep 16, 2002 at 03:49:27PM +0100, Alan Cox wrote: >>>> Also does turning off the nmi watchdog junk make the box stable ? >>> >>> good idea, I didn't though about this one since I only heard the nmi >>> to >>> lockup hard boxes after hours of load, never to generate any >>> malfunction, but certainly the nmi handling isn't probably one of the >>> most exercised hardware paths in the cpus, so it's a good idea to >>> reproduce with it turned off (OTOH I guess you probably turned it on >>> explicitly only after you got these troubles, in order to debug them). >>> >> >> I only turned the nmi watchdog on, on the one "unknown" version Oops. >> >> This box was running fine with 2.4.18-SuSE with uptimes 40+days. _Now_ >> I am almost sure, that it's _not_ a hardware problem (FENCE counting >> here as software - since there is a software workaround). >> >> I had 3 lockups in 2 days, when I switched to 2.4.19 - and even lower >> room temperature. No, there _must_ be a bug :) > > possible. Which was the previous kernel running in the machine before > 2.4.18-SuSE? > I guess 2.4.10-SuSE from 7.3 In january I switched to 2.4.14 and 2.4.17 and applied the xfs patches. At exactly the same instruction: kaboom! http://marc.theaimsgroup.com/?l=linux-kernel&m=101113532211430&w=2 >> Can someone explain me the difference for label 1 and 2? >> Why is the "js 2f" there? This I don't understand fully - >> it looks broken to me. > > it's correct, if not we would have noticed since a long time ;) > > What it does is to subtract 1 to the lock, if it goes negative (signed) > it jumps into the looping slow path (label 2), then when it finally > stops looping because it acquired the lock, it jumps back to 1 and > enters the critical section. The slow path takes care of acquiring the > lock internally, first polling and doing without requiring the cacheline > exclusive the trylock again. After studying the disassembly I now see the "trick" with a jump to a new section. >> >> include/asm-i386/rwlock.h >> >> #define __build_read_lock_ptr(rw, helper) \ >> asm volatile(LOCK "subl $1,(%0)\n\t" \ >> "js 2f\n" \ >> "1:\n" \ >> LOCK_SECTION_START("") \ >> "2:\tcall " helper "\n\t" \ >> "jmp 1b\n" \ >> LOCK_SECTION_END \ >> ::"a" (rw) : "memory") - 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/