x86, UV: Make kdump avoid stack dumps (5edd19af) · Commits · 戴 / test

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>

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();

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