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kgdb, x86: Avoid invoking kgdb_nmicallback twice per NMI

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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>
This commit is contained in:
Jan Kiszka 2008-10-06 13:50:59 -05:00 committed by Jason Wessel
parent fec6ed1d1f
commit e85ceae910
1 changed files with 1 additions and 6 deletions
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7
arch/x86/kernel/kgdb.c
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@ -455,12 +455,7 @@ static int __kgdb_notify(struct die_args *args, unsigned long cmd)
return NOTIFY_DONE; return NOTIFY_DONE;
case DIE_NMI_IPI: case DIE_NMI_IPI:
if (atomic_read(&kgdb_active) != -1) { /* Just ignore, we will handle the roundup on DIE_NMI. */
/* KGDB CPU roundup */
kgdb_nmicallback(raw_smp_processor_id(), regs);
was_in_debug_nmi[raw_smp_processor_id()] = 1;
touch_nmi_watchdog();
}
return NOTIFY_DONE; return NOTIFY_DONE;
case DIE_NMIUNKNOWN: case DIE_NMIUNKNOWN: