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Commit 5edd19af authored by Cliff Wickman's avatar Cliff Wickman Committed by H. Peter Anvin
Browse files

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: default avatarCliff Wickman <cpw@sgi.com>
LKML-Reference: <E1ObLvt-0005UZ-Va@eag09.americas.sgi.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 93a7ca0c

arch/x86/include/asm/kdebug.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/kernel/apic/x2apic_uv_x.c

+4 −0
Original line number Diff line number Diff line
@@ -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.

arch/x86/kernel/crash.c

+3 −0
Original line number Diff line number Diff line
@@ -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();