[PATCH] x86: Add abilty to enable/disable nmi watchdog with sysctl

Adds a new /proc/sys/kernel/nmi call that will enable/disable the nmi
watchdog.

Signed-off-by:  Don Zickus <dzickus@redhat.com>
Signed-off-by: Andi Kleen <ak@suse.de>

1 files changed, 48 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index 9d175dcf3a2..3a17411a9a1 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -750,6 +750,54 @@ static int unknown_nmi_panic_callback(struct pt_regs *regs, int cpu)
         return 0;
 }
 
+/*
+ * proc handler for /proc/sys/kernel/nmi
+ */
+int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file,
+                        void __user *buffer, size_t *length, loff_t *ppos)
+{
+        int old_state;
+
+        nmi_watchdog_enabled = (atomic_read(&nmi_active) > 0) ? 1 : 0;
+        old_state = nmi_watchdog_enabled;
+        proc_dointvec(table, write, file, buffer, length, ppos);
+        if (!!old_state == !!nmi_watchdog_enabled)
+                return 0;
+
+        if (atomic_read(&nmi_active) < 0) {
+                printk( KERN_WARNING "NMI watchdog is permanently disabled\n");
+                return -EINVAL;
+        }
+
+        /* if nmi_watchdog is not set yet, then set it */
+        nmi_watchdog_default();
+
+        if (nmi_watchdog == NMI_LOCAL_APIC)
+        {
+                if (nmi_watchdog_enabled)
+                        enable_lapic_nmi_watchdog();
+                else
+                        disable_lapic_nmi_watchdog();
+        } else if (nmi_watchdog == NMI_IO_APIC) {
+                /* FIXME
+                 * for some reason these functions don't work
+                 */
+                printk("Can not enable/disable NMI on IO APIC\n");
+                return -EIO;
+#if 0
+                if (nmi_watchdog_enabled)
+                        enable_timer_nmi_watchdog();
+                else
+                        disable_timer_nmi_watchdog();
+#endif
+        } else {
+                printk(KERN_WARNING
+                        "NMI watchdog doesn't know what hardware to touch\n");
+                return -EIO;
+        }
+        return 0;
+}
+
 #endif
 
 EXPORT_SYMBOL(nmi_active);