Commit e85ceae9 authored Oct 06, 2008 by Jan Kiszka Committed by Jason Wessel Oct 06, 2008

kgdb, x86: Avoid invoking kgdb_nmicallback twice per NMI

Stress-testing KVM's latest NMI support with kgdbts inside an SMP guest,
I came across spurious unhandled NMIs while running the singlestep test.
Looking closer at the code path each NMI takes when KGDB is enabled, I
noticed that kgdb_nmicallback is called twice per event: One time via
DIE_NMI_IPI notification, the second time on DIE_NMI. Removing the first
invocation cures the unhandled NMIs here.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>

parent fec6ed1d

arch/x86/kernel/kgdb.c

+1 −6

Original line number	Diff line number	Diff line
		@@ -455,12 +455,7 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
		return NOTIFY_DONE;

		case DIE_NMI_IPI:
		if (atomic_read(&kgdb_active) != -1) {
		/* KGDB CPU roundup */
		kgdb_nmicallback(raw_smp_processor_id(), regs);
		was_in_debug_nmi[raw_smp_processor_id()] = 1;
		touch_nmi_watchdog();
		}
		/* Just ignore, we will handle the roundup on DIE_NMI. */
		return NOTIFY_DONE;

		case DIE_NMIUNKNOWN:

Admin message