cpumask: Avoid cpumask_t in arch/x86/kernel/apic/nmi.c

Ingo wants the certainty of a static cpumask (rather than a
cpumask_var_t), but cpumask_t will some day be undefined to
avoid on-stack declarations.

This is what DECLARE_BITMAP/to_cpumask() is for.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
LKML-Reference: <200911031453.52394.rusty@rustcorp.com.au>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/apic/nmi.c

@@ -39,7 +39,8 @@
 int unknown_nmi_panic;
 int nmi_watchdog_enabled;
 
-static cpumask_t backtrace_mask __read_mostly;
+/* For reliability, we're prepared to waste bits here. */
+static DECLARE_BITMAP(backtrace_mask, NR_CPUS) __read_mostly;
 
 /* nmi_active:
  * >0: the lapic NMI watchdog is active, but can be disabled
@@ -414,7 +415,7 @@ nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 	}
 
 	/* We can be called before check_nmi_watchdog, hence NULL check. */
-	if (cpumask_test_cpu(cpu, &backtrace_mask)) {
+	if (cpumask_test_cpu(cpu, to_cpumask(backtrace_mask))) {
 		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */
 
 		spin_lock(&lock);
@@ -422,7 +423,7 @@ nmi_watchdog_tick(struct pt_regs *regs, unsigned reason)
 		show_regs(regs);
 		dump_stack();
 		spin_unlock(&lock);
-		cpumask_clear_cpu(cpu, &backtrace_mask);
+		cpumask_clear_cpu(cpu, to_cpumask(backtrace_mask));
 
 		rc = 1;
 	}
@@ -558,14 +559,14 @@ void arch_trigger_all_cpu_backtrace(void)
 {
 	int i;
 
-	cpumask_copy(&backtrace_mask, cpu_online_mask);
+	cpumask_copy(to_cpumask(backtrace_mask), cpu_online_mask);
 
 	printk(KERN_INFO "sending NMI to all CPUs:\n");
 	apic->send_IPI_all(NMI_VECTOR);
 
 	/* Wait for up to 10 seconds for all CPUs to do the backtrace */
 	for (i = 0; i < 10 * 1000; i++) {
-		if (cpumask_empty(&backtrace_mask))
+		if (cpumask_empty(to_cpumask(backtrace_mask)))
 			break;
 		mdelay(1);
 	}