From: Jan Kiszka <jan.kiszka@siemens.com>
Date: Mon, 6 Oct 2008 18:50:59 +0000 (-0500)
Subject: kgdb, x86: Avoid invoking kgdb_nmicallback twice per NMI
X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=e85ceae9102f6e3c1d707e7ac88fa48d252e9cfa;p=GitHub%2Fexynos8895%2Fandroid_kernel_samsung_universal8895.git

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>
---

diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c
index 8282a2139681..10435a120d22 100644
--- a/arch/x86/kernel/kgdb.c
+++ b/arch/x86/kernel/kgdb.c
@@ -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: