[kernel] Disable soft lockup detector on virtual machines. (rhbz 971139)

[Dave Jones]

commit 18e50ce8f8d390b47ed295bbe96566c6bccf7e6f
Author: Dave Jones <davej at redhat.com>
Date:   Tue Jun 11 16:36:11 2013 -0400

    Disable soft lockup detector on virtual machines. (rhbz 971139)

 kernel.spec              |    8 +++++
 nowatchdog-on-virt.patch |   67 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 75 insertions(+), 0 deletions(-)
---
diff --git a/kernel.spec b/kernel.spec
index 9e1d7da..50da9e5 100644
--- a/kernel.spec
+++ b/kernel.spec
@@ -694,6 +694,8 @@ Patch14000: hibernate-freeze-filesystems.patch
 
 Patch14010: lis3-improve-handling-of-null-rate.patch
 
+Patch15000: nowatchdog-on-virt.patch
+
 
 # ARM
 Patch21000: arm-export-read_current_timer.patch
@@ -1418,6 +1420,9 @@ ApplyPatch efi-dont-map-boot-services-on-32bit.patch
 
 ApplyPatch lis3-improve-handling-of-null-rate.patch
 
+# Disable watchdog on virtual machines.
+ApplyPatch nowatchdog-on-virt.patch
+
 #rhbz 754518
 ApplyPatch scsi-sd_revalidate_disk-prevent-NULL-ptr-deref.patch
 
@@ -2278,6 +2283,9 @@ fi
 #                 ||----w |
 #                 ||     ||
 %changelog
+* Tue Jun 11 2013 Dave Jones <davej at redhat.com>
+- Disable soft lockup detector on virtual machines. (rhbz 971139)
+
 * Tue Jun 11 2013 Josh Boyer <jwboyer at redhat.com>
 - Add patches to fix MTRR issues in 3.9.5 (rhbz 973185)
 - Add two patches to fix issues with vhost_net and macvlan (rhbz 954181)
diff --git a/nowatchdog-on-virt.patch b/nowatchdog-on-virt.patch
new file mode 100644
index 0000000..b206422
--- /dev/null
+++ b/nowatchdog-on-virt.patch
@@ -0,0 +1,67 @@
+Disable watchdog on virtual machines.
+
+For various reasons, VMs seem to trigger the soft lockup detector a lot,
+in cases where it's just not possible for a lockup to occur.
+(Example: https://bugzilla.redhat.com/show_bug.cgi?id=971139)
+
+In some cases it seems that the host just never scheduled the app running
+the VM for a very long time (Could be the host was under heavy load).
+
+Just disable the detector on VMs.
+
+Signed-off-by: Dave Jones <davej at redhat.com>
+
+diff --git a/kernel/watchdog.c b/kernel/watchdog.c
+index 05039e3..a28aab9 100644
+--- a/kernel/watchdog.c
++++ b/kernel/watchdog.c
+@@ -24,6 +24,7 @@
+ #include <linux/sysctl.h>
+ #include <linux/smpboot.h>
+ #include <linux/sched/rt.h>
++#include <linux/dmi.h>
+ 
+ #include <asm/irq_regs.h>
+ #include <linux/kvm_para.h>
+@@ -96,6 +97,32 @@ static int __init nosoftlockup_setup(char *str)
+ __setup("nosoftlockup", nosoftlockup_setup);
+ /*  */
+ 
++static int disable_watchdog(const struct dmi_system_id *d)
++{
++	printk(KERN_INFO "watchdog: disabled (inside virtual machine)\n");
++	watchdog_enabled = 0;
++	return 0;
++}
++
++static const struct dmi_system_id watchdog_virt_dmi_table[] = {
++	{
++		.callback = disable_watchdog,
++		.ident = "VMware",
++		.matches = {
++			DMI_MATCH(DMI_SYS_VENDOR, "VMware, Inc."),
++		},
++	},
++	{
++		.callback = disable_watchdog,
++		.ident = "Bochs",
++		.matches = {
++			DMI_MATCH(DMI_SYS_VENDOR, "Bochs Bochs"),
++		},
++	},
++	{}
++};
++
++
+ /*
+  * Hard-lockup warnings should be triggered after just a few seconds. Soft-
+  * lockups can have false positives under extreme conditions. So we generally
+@@ -543,6 +570,8 @@ static struct smp_hotplug_thread watchdog_threads = {
+ 
+ void __init lockup_detector_init(void)
+ {
++	dmi_check_system(watchdog_virt_dmi_table);
++
+ 	set_sample_period();
+ 	if (smpboot_register_percpu_thread(&watchdog_threads)) {
+ 		pr_err("Failed to create watchdog threads, disabled\n");