[patch, -rc5-mm1] lock validator: disable NMI watchdog if CONFIG_LOCKDEP, i386

[Ingo Molnar <mingo@elte.hu>]

* Mike Galbraith <efault@gmx.de> wrote:

> > > BUG: warning at kernel/lockdep.c:2398/check_flags()
> > 
> > this one could be related to NMI. We are already disabling NMI on 
> > x86_64, but i thought i had it fixed up for i386 - apparently not.
> 
> Booted with nmi_watchdog=0, no warning and no deadlock.

ok, great. The patch below turns off NMI on i386 automatically.

-------------------
Subject: lock validator: disable NMI watchdog if CONFIG_LOCKDEP, i386
From: Ingo Molnar <mingo@elte.hu>

The NMI watchdog uses spinlocks (notifier chains, etc.),
so it's not lockdep-safe at the moment.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/i386/kernel/nmi.c |   11 +++++++++++
 1 file changed, 11 insertions(+)

Index: linux/arch/i386/kernel/nmi.c
===================================================================
--- linux.orig/arch/i386/kernel/nmi.c
+++ linux/arch/i386/kernel/nmi.c
@@ -741,6 +741,17 @@ static void stop_intel_arch_watchdog(voi
 
 void setup_apic_nmi_watchdog (void *unused)
 {
+#ifdef CONFIG_LOCKDEP
+	/*
+	 * The NMI watchdog uses spinlocks (notifier chains, etc.),
+	 * so it's not lockdep-safe:
+	 */
+	nmi_watchdog = NMI_NONE;
+	printk("lockdep: disabled NMI watchdog.\n");
+
+	return;
+#endif
+
 	/* only support LOCAL and IO APICs for now */
 	if ((nmi_watchdog != NMI_LOCAL_APIC) &&
 	    (nmi_watchdog != NMI_IO_APIC))