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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>
This commit is contained in:
Cliff Wickman 2010-07-20 18:09:05 -05:00 committed by H. Peter Anvin
parent 93a7ca0c3e
commit 5edd19af18
3 changed files with 8 additions and 0 deletions
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1
arch/x86/include/asm/kdebug.h
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@ -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 */

4
arch/x86/kernel/apic/x2apic_uv_x.c
View File

@ -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.

3
arch/x86/kernel/crash.c
View File

@ -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_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();