Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933111Ab0GTXIo (ORCPT ); Tue, 20 Jul 2010 19:08:44 -0400 Received: from relay2.sgi.com ([192.48.179.30]:57753 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932946Ab0GTXIn (ORCPT ); Tue, 20 Jul 2010 19:08:43 -0400 To: linux-kernel@vger.kernel.org Subject: [PATCH] x86, UV: make kdump avoid stack dumps Cc: mingo@elte.hu, hpa@zytor.com Message-Id: From: Cliff Wickman Date: Tue, 20 Jul 2010 18:09:05 -0500 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3105 Lines: 83 This patch is the same as one sent Jun18 2010. It doesn't seem to have been noticed. UV NMI callback's should not write stack dumps when a kdump is to be written. When invoking the crash kernel to write a dump, kdump_nmi_shootdown_cpus() uses NMI's to get all the cpu's to save their register context and halt. But the NMI interrupt handler runs a callback list. This patch sets a flag to prevent any of those callbacks from interfering with the halt of the cpu. For UV, which currently has the only callback to which this is relevant, the uv_handle_nmi() callback should not do dumping of stacks. The 'in_crash_kexec' flag is defined as an extern in kdebug.h firstly because x2apic_uv_x.c includes it. Secondly because some future callback might need the flag to know that it should not enter the debugger. (Such a scenario was in fact present in the 2.6.32 kernel, SuSE distribution, where a call to kdb needed to be avoided.) Diffed against 2.6.35 Signed-off-by: Cliff Wickman --- arch/x86/include/asm/kdebug.h | 1 + arch/x86/kernel/apic/x2apic_uv_x.c | 4 ++++ arch/x86/kernel/crash.c | 3 +++ 3 files changed, 8 insertions(+) Index: linux-2.6.35-rc3/arch/x86/kernel/apic/x2apic_uv_x.c =================================================================== --- linux-2.6.35-rc3.orig/arch/x86/kernel/apic/x2apic_uv_x.c +++ linux-2.6.35-rc3/arch/x86/kernel/apic/x2apic_uv_x.c @@ -604,6 +604,10 @@ int uv_handle_nmi(struct notifier_block { if (reason != DIE_NMI_IPI) return NOTIFY_OK; + + if (in_crash_kexec) + /* do nothing if entering the crash kernel */ + return NOTIFY_OK; /* * Use a lock so only one cpu prints at a time * to prevent intermixed output. Index: linux-2.6.35-rc3/arch/x86/kernel/crash.c =================================================================== --- linux-2.6.35-rc3.orig/arch/x86/kernel/crash.c +++ linux-2.6.35-rc3/arch/x86/kernel/crash.c @@ -28,6 +28,8 @@ #include #include +int in_crash_kexec; + #if defined(CONFIG_SMP) && defined(CONFIG_X86_LOCAL_APIC) static void kdump_nmi_callback(int cpu, struct die_args *args) @@ -61,6 +63,7 @@ static void kdump_nmi_callback(int cpu, static void kdump_nmi_shootdown_cpus(void) { + in_crash_kexec = 1; nmi_shootdown_cpus(kdump_nmi_callback); disable_local_APIC(); Index: linux-2.6.35-rc3/arch/x86/include/asm/kdebug.h =================================================================== --- linux-2.6.35-rc3.orig/arch/x86/include/asm/kdebug.h +++ linux-2.6.35-rc3/arch/x86/include/asm/kdebug.h @@ -33,5 +33,6 @@ extern void __show_regs(struct pt_regs * extern void show_regs(struct pt_regs *regs); extern unsigned long oops_begin(void); extern void oops_end(unsigned long, struct pt_regs *, int signr); +extern int in_crash_kexec; #endif /* _ASM_X86_KDEBUG_H */ -- 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/