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 <cpw@sgi.com>
LKML-Reference: <E1ObLvt-0005UZ-Va@eag09.americas.sgi.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c
index ebd4c51..764c7c2 100644
--- a/arch/x86/kernel/crash.c
+++ b/arch/x86/kernel/crash.c
@@ -28,6 +28,8 @@
#include <asm/reboot.h>
#include <asm/virtext.h>
+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_shootdown_cpus(void)
{
+ in_crash_kexec = 1;
nmi_shootdown_cpus(kdump_nmi_callback);
disable_local_APIC();