From 5edd19af18a36a4e22c570b1b969179e0ca1fe4c Mon Sep 17 00:00:00 2001 From: Cliff Wickman Date: Tue, 20 Jul 2010 18:09:05 -0500 Subject: [PATCH] x86, UV: Make kdump avoid stack dumps 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.) Signed-off-by: Cliff Wickman LKML-Reference: Signed-off-by: H. Peter Anvin --- 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(+) diff --git a/arch/x86/include/asm/kdebug.h b/arch/x86/include/asm/kdebug.h index fa7c0b974761..7a2910b3512b 100644 --- a/arch/x86/include/asm/kdebug.h +++ b/arch/x86/include/asm/kdebug.h @@ -33,5 +33,6 @@ extern void __show_regs(struct pt_regs *regs, int all); 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 */ diff --git a/arch/x86/kernel/apic/x2apic_uv_x.c b/arch/x86/kernel/apic/x2apic_uv_x.c index e46f98f36e31..7b598b84c902 100644 --- a/arch/x86/kernel/apic/x2apic_uv_x.c +++ b/arch/x86/kernel/apic/x2apic_uv_x.c @@ -604,6 +604,10 @@ int uv_handle_nmi(struct notifier_block *self, unsigned long reason, void *data) { 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. diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c index ebd4c51d096a..764c7c2b1811 100644 --- a/arch/x86/kernel/crash.c +++ b/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, struct die_args *args) static void kdump_nmi_shootdown_cpus(void) { + in_crash_kexec = 1; nmi_shootdown_cpus(kdump_nmi_callback); disable_local_APIC(); -- GitLab