Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755667AbYJQVCf (ORCPT ); Fri, 17 Oct 2008 17:02:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752506AbYJQVC2 (ORCPT ); Fri, 17 Oct 2008 17:02:28 -0400 Received: from charlotte.tuxdriver.com ([70.61.120.58]:45202 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751954AbYJQVC1 (ORCPT ); Fri, 17 Oct 2008 17:02:27 -0400 Date: Fri, 17 Oct 2008 17:00:13 -0400 From: Neil Horman To: kexec@lists.infradead.org, linux-kernel@vger.kernel.org Cc: vgoyal@redhat.com, hbabu@us.ibm.com, ebiederm@xmission.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, nhorman@tuxdriver.com, akpm@linux-foundation.org Subject: [PATCH] kexec: fix hang on i386 when panic occurs while console_sem is held Message-ID: <20081017210013.GD23591@hmsreliant.think-freely.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) X-Spam-Score: -1.4 (-) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1844 Lines: 52 Hey all- Theres a corner case in 32 bit x86 kdump at the moment. When the box panics via nmi, we call bust_spinlocks(1) to disable sensitivity to the console_sem (allowing us to print to the console in all cases), but we don't call crash_kexec, until after we call bust_spinlocks(0), which re-enables console_sem sensitivity. The result is that, if we get an nmi while the console_sem is held and kdump is configured, and we try to print something to the console during kdump shutdown (which we often do) we deadlock the box. The fix is to simply do what 64 bit die_nmi does which is to not call bust_spinlocks(0) until after we call crash_kexec. Patch below tested successfully by me: Regards Neil Signed-off-by: Neil Horman dumpstack_32.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c index 1a78180..b361475 100644 --- a/arch/x86/kernel/dumpstack_32.c +++ b/arch/x86/kernel/dumpstack_32.c @@ -405,7 +405,6 @@ die_nmi(char *str, struct pt_regs *regs, int do_panic) panic("Non maskable interrupt"); console_silent(); spin_unlock(&nmi_print_lock); - bust_spinlocks(0); /* * If we are in kernel we are probably nested up pretty bad @@ -416,6 +415,7 @@ die_nmi(char *str, struct pt_regs *regs, int do_panic) crash_kexec(regs); } + bust_spinlocks(0); do_exit(SIGSEGV); } -- /**************************************************** * Neil Horman * Software Engineer, Red Hat ****************************************************/ -- 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/