From: Ingo Molnar <mingo@elte.hu>
Date: Thu, 5 Jun 2008 09:17:16 +0000 (+0200)
Subject: x86, io-apic: fix nmi_watchdog=1 bootup hang
X-Git-Tag: v2.6.27-rc1~1106^2~251^2~13
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ff11571b25152edfb1eb0e6feb7e0009670fe4a5;p=linux-2.6

x86, io-apic: fix nmi_watchdog=1 bootup hang

nmi_watchdog=1 hangs on 64-bit:

[    0.250000] Detected 12.564 MHz APIC timer.
[    0.254178] APIC timer registered as dummy, due to nmi_watchdog=1!
[    0.260366] Testing NMI watchdog ... <4>WARNING: CPU#0: NMI appears to be stuck (0->0)!
[    ...     ]
[    0.470003] calling  genl_init+0x0/0xd0
[  hard hang ]

bisected it down to:

 git-bisect start
 git-bisect good 1beee8dc8cf58e3f605bd7b34d7a39939be7d8d2
 git-bisect bad 11582ece0aaa2d0f94f345c08a4ab9997078a083
 git-bisect bad 5479c623bb44089844022c03d4c0eb16d5b7a15f
 git-bisect bad cfb4c7fabeb499e1c29f9d1878968e37a938e28a
 git-bisect good 246dd412d31e4f5de1d43aa6422a325b785f36e4
 git-bisect bad 3f8237eaff7dc1e35fa791dae095574fd974e671
 git-bisect good 90e23b13ab849e2a11f00c655eb3a2011b4623be
 git-bisect bad 833526a34eeefc117df3191a594c3c3a4f15a9ac
 git-bisect good 791b93d3dfaf16c23e978bec0cc0a3dd9d855d63
 git-bisect bad 65767c64068f2c93e56a1accfed5c78230ac12d7
 git-bisect bad 2abc5c05dd82c188e3bdf6641a274f013348d14b
 git-bisect bad 317e1f2597ffb4d4db940577bbe56dc6e881ef07

| 317e1f2597ffb4d4db940577bbe56dc6e881ef07 is first bad commit
| commit 317e1f2597ffb4d4db940577bbe56dc6e881ef07
| Author: Maciej W. Rozycki <macro@linux-mips.org>
| Date:   Wed May 21 22:10:22 2008 +0100
|     x86: I/O APIC: clean up the 8259A on a NMI watchdog failure

the problem is that in the dummy-lapic branch we rely on the i8259A
but if the NMI watchdog fails we turn off IRQ 0 - which doesnt work
too well ;-)

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/arch/x86/kernel/apic_32.c b/arch/x86/kernel/apic_32.c
index 4b99b1bdeb..3cebf91d50 100644
--- a/arch/x86/kernel/apic_32.c
+++ b/arch/x86/kernel/apic_32.c
@@ -541,11 +541,13 @@ void __init setup_boot_APIC_clock(void)
 		 * PIT/HPET going.  Otherwise register lapic as a dummy
 		 * device.
 		 */
-		if (nmi_watchdog != NMI_IO_APIC)
+		if (nmi_watchdog != NMI_IO_APIC) {
 			lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;
-		else
+		} else {
 			printk(KERN_WARNING "APIC timer registered as dummy,"
 			       " due to nmi_watchdog=1!\n");
+			timer_through_8259 = 1;
+		}
 	}
 
 	/* Setup the lapic or request the broadcast */
diff --git a/arch/x86/kernel/apic_64.c b/arch/x86/kernel/apic_64.c
index 07fda23a9f..6cbc668a4c 100644
--- a/arch/x86/kernel/apic_64.c
+++ b/arch/x86/kernel/apic_64.c
@@ -413,11 +413,13 @@ void __init setup_boot_APIC_clock(void)
 	 * PIT/HPET going.  Otherwise register lapic as a dummy
 	 * device.
 	 */
-	if (nmi_watchdog != NMI_IO_APIC)
+	if (nmi_watchdog != NMI_IO_APIC) {
 		lapic_clockevent.features &= ~CLOCK_EVT_FEAT_DUMMY;
-	else
+	} else {
 		printk(KERN_WARNING "APIC timer registered as dummy,"
 		       " due to nmi_watchdog=1!\n");
+		timer_through_8259 = 1;
+	}
 
 	setup_APIC_timer();
 }