sparc64: Manage NMI watchdog enabling like x86.

Use a per-cpu 'wd_enabled' boolean and a global atomic_t count
of watchdog NMI enabled cpus which is set to '-1' if something
is wrong with the watchdog and it can't be used.

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/include/asm/nmi.h

@@ -5,6 +5,6 @@ extern int __init nmi_init(void);
 extern void perfctr_irq(int irq, struct pt_regs *regs);
 extern void nmi_adjust_hz(unsigned int new_hz);
 
-extern int nmi_usable;
+extern atomic_t nmi_active;
 
 #endif /* __NMI_H */

arch/sparc/kernel/nmi.c

@@ -34,10 +34,17 @@
 static int nmi_watchdog_active;
 static int panic_on_timeout;
 
-int nmi_usable;
-EXPORT_SYMBOL_GPL(nmi_usable);
+/* nmi_active:
+ * >0: the NMI watchdog is active, but can be disabled
+ * <0: the NMI watchdog has not been set up, and cannot be enabled
+ *  0: the NMI watchdog is disabled, but can be enabled
+ */
+atomic_t nmi_active = ATOMIC_INIT(0);		/* oprofile uses this */
+EXPORT_SYMBOL(nmi_active);
 
 static unsigned int nmi_hz = HZ;
+static DEFINE_PER_CPU(short, wd_enabled);
+static int endflag __initdata;
 
 static DEFINE_PER_CPU(unsigned int, last_irq_sum);
 static DEFINE_PER_CPU(local_t, alert_counter);
@@ -110,7 +117,7 @@ notrace __kprobes void perfctr_irq(int irq, struct pt_regs *regs)
 		__get_cpu_var(last_irq_sum) = sum;
 		local_set(&__get_cpu_var(alert_counter), 0);
 	}
-	if (nmi_usable) {
+	if (__get_cpu_var(wd_enabled)) {
 		write_pic(picl_value(nmi_hz));
 		pcr_ops->write(pcr_enable);
 	}
@@ -121,8 +128,6 @@ static inline unsigned int get_nmi_count(int cpu)
 	return cpu_data(cpu).__nmi_count;
 }
 
-static int endflag __initdata;
-
 static __init void nmi_cpu_busy(void *data)
 {
 	local_irq_enable_in_hardirq();
@@ -143,19 +148,25 @@ static void report_broken_nmi(int cpu, int *prev_nmi_count)
 	printk(KERN_WARNING
 		"and attach the output of the 'dmesg' command.\n");
 
-	nmi_usable = 0;
+	per_cpu(wd_enabled, cpu) = 0;
+	atomic_dec(&nmi_active);
 }
 
-static void stop_watchdog(void *unused)
+static void stop_nmi_watchdog(void *unused)
 {
 	pcr_ops->write(PCR_PIC_PRIV);
+	__get_cpu_var(wd_enabled) = 0;
+	atomic_dec(&nmi_active);
 }
 
 static int __init check_nmi_watchdog(void)
 {
 	unsigned int *prev_nmi_count;
 	int cpu, err;
 
+	if (!atomic_read(&nmi_active))
+		return 0;
+
 	prev_nmi_count = kmalloc(nr_cpu_ids * sizeof(unsigned int), GFP_KERNEL);
 	if (!prev_nmi_count) {
 		err = -ENOMEM;
@@ -172,12 +183,15 @@ static int __init check_nmi_watchdog(void)
 	mdelay((20 * 1000) / nmi_hz); /* wait 20 ticks */
 
 	for_each_online_cpu(cpu) {
+		if (!per_cpu(wd_enabled, cpu))
+			continue;
 		if (get_nmi_count(cpu) - prev_nmi_count[cpu] <= 5)
 			report_broken_nmi(cpu, prev_nmi_count);
 	}
 	endflag = 1;
-	if (!nmi_usable) {
+	if (!atomic_read(&nmi_active)) {
 		kfree(prev_nmi_count);
+		atomic_set(&nmi_active, -1);
 		err = -ENODEV;
 		goto error;
 	}
@@ -188,12 +202,26 @@ static int __init check_nmi_watchdog(void)
 	kfree(prev_nmi_count);
 	return 0;
 error:
-	on_each_cpu(stop_watchdog, NULL, 1);
+	on_each_cpu(stop_nmi_watchdog, NULL, 1);
 	return err;
 }
 
-static void start_watchdog(void *unused)
+static void start_nmi_watchdog(void *unused)
+{
+	__get_cpu_var(wd_enabled) = 1;
+	atomic_inc(&nmi_active);
+
+	pcr_ops->write(PCR_PIC_PRIV);
+	write_pic(picl_value(nmi_hz));
+
+	pcr_ops->write(pcr_enable);
+}
+
+static void nmi_adjust_hz_one(void *unused)
 {
+	if (!__get_cpu_var(wd_enabled))
+		return;
+
 	pcr_ops->write(PCR_PIC_PRIV);
 	write_pic(picl_value(nmi_hz));
 
@@ -203,13 +231,13 @@ static void start_watchdog(void *unused)
 void nmi_adjust_hz(unsigned int new_hz)
 {
 	nmi_hz = new_hz;
-	on_each_cpu(start_watchdog, NULL, 1);
+	on_each_cpu(nmi_adjust_hz_one, NULL, 1);
 }
 EXPORT_SYMBOL_GPL(nmi_adjust_hz);
 
 static int nmi_shutdown(struct notifier_block *nb, unsigned long cmd, void *p)
 {
-	on_each_cpu(stop_watchdog, NULL, 1);
+	on_each_cpu(stop_nmi_watchdog, NULL, 1);
 	return 0;
 }
 
@@ -221,16 +249,14 @@ int __init nmi_init(void)
 {
 	int err;
 
-	nmi_usable = 1;
-
-	on_each_cpu(start_watchdog, NULL, 1);
+	on_each_cpu(start_nmi_watchdog, NULL, 1);
 
 	err = check_nmi_watchdog();
 	if (!err) {
 		err = register_reboot_notifier(&nmi_reboot_notifier);
 		if (err) {
-			nmi_usable = 0;
-			on_each_cpu(stop_watchdog, NULL, 1);
+			on_each_cpu(stop_nmi_watchdog, NULL, 1);
+			atomic_set(&nmi_active, -1);
 		}
 	}
 	return err;

arch/sparc/oprofile/init.c

@@ -57,7 +57,7 @@ static void timer_stop(void)
 
 static int op_nmi_timer_init(struct oprofile_operations *ops)
 {
-	if (!nmi_usable)
+	if (atomic_read(&nmi_active) <= 0)
 		return -ENODEV;
 
 	ops->start = timer_start;