Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757049AbYB1JRW (ORCPT ); Thu, 28 Feb 2008 04:17:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752893AbYB1JRH (ORCPT ); Thu, 28 Feb 2008 04:17:07 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:37996 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752664AbYB1JRC (ORCPT ); Thu, 28 Feb 2008 04:17:02 -0500 Date: Thu, 28 Feb 2008 10:16:39 +0100 From: Ingo Molnar To: "Klaus S. Madsen" Cc: LKML , Pavel Machek , "Rafael J. Wysocki" , "H. Peter Anvin" , Thomas Gleixner Subject: Re: Regression in 2.6.25-rc3: s2ram segfaults before suspending Message-ID: <20080228091639.GB1133@elte.hu> References: <20080227221033.GR17932@hjernemadsen.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080227221033.GR17932@hjernemadsen.org> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2572 Lines: 70 * Klaus S. Madsen wrote: > Hi all, > > I have a Thinkpad T61p, which I'm able to suspend with s2ram > on Linux 2.6.24.3. However when I try to suspend it on 2.6.25-rc3, > s2ram dies after changing to vt1, with a segfault. I'm using s2ram > from cvs, and libx86 version 0.99 from > http://www.codon.org.uk/~mjg59/libx86/. > > Some details about the segfault: > > $ sudo gdb ./s2ram > (gdb) run > Starting program: /home/ksm/downloads/suspend/s2ram > Switching from vt7 to vt1 > Calling get_mode > > Program received signal SIGSEGV, Segmentation fault. > 0xb7facf4a in run_vm86 () at lrmi.c:526 > 526 asm volatile ( > (gdb) list > 521 static int > 522 lrmi_vm86(struct vm86_struct *vm) > 523 { > 524 int r; > 525 #ifdef __PIC__ > 526 asm volatile ( > 527 "pushl %%ebx\n\t" > 528 "movl %2, %%ebx\n\t" > 529 "int $0x80\n\t" > 530 "popl %%ebx" > (gdb) bt > #0 0xb7facf4a in run_vm86 () at lrmi.c:526 > #1 0xb7fad61b in LRMI_int (i=16, r=0xbffca670) at lrmi.c:844 > #2 0x0804acfc in do_vbe_service (AX=20227, BX=0, regs=0xbffca670) > at vbetool/vbetool.c:158 > #3 0x0804af7e in __get_mode () at vbetool/vbetool.c:453 > #4 0x0804a30f in s2ram_hacks () at s2ram-x86.c:268 > #5 0x0804954f in main (argc=1, argv=0x0) at s2ram-main.c:92 > > I have tried to bisect the problem, and it fingered the following > commit: > > commit 82bc03fc158e28c90d7ed9919410776039cb4e14 > Author: Ingo Molnar > > x86: add PWT to NOCACHE flags > > Reverting this commit in the bisected tree (by executing git show > 82bc03fc158e28c90d7ed9919410776039cb4e14 | patch -R -p1), makes the > segfault go away. I've run make clean between each kernel compile, to > be sure the tree was correctly compiled. thanks for tracking this down. It would be nice to figure out why this change made a difference. Perhaps VM86 mode has some restrictions in what type of pagetables it can operate in - and the CPU just refuses to properly emulate those 16-bit instructions? (this would be very weird). We are trying to execute 16-bit BIOS code here, right? which instruction is the segfault coming from - the int $0x80? So in vm86 mode we generated a #GPF which shows up as a SIGSEGV? Ingo -- 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/