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Commit fcef8576 authored by Rusty Russell's avatar Rusty Russell
Browse files

cpumask: convert arch/x86/kernel/nmi.c's backtrace_mask to a cpumask_var_t 



Impact: cleanup, reduce memory usage for CONFIG_CPUMASK_OFFSTACK=y

I *think* every path calls check_nmi_watchdog before using the
watchdog, so that's the right place for the initialization.

If that's wrong, we'll get a nice NULL-deref with
CONFIG_CPUMASK_OFFSTACK=y, and have uncovered another bug.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent bc9b83dd

arch/x86/kernel/apic/nmi.c

+6 −5
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ 
int unknown_nmi_panic;

int nmi_watchdog_enabled;



static cpumask_t backtrace_mask = CPU_MASK_NONE;

static cpumask_var_t backtrace_mask;



/* nmi_active:

 * >0: the lapic NMI watchdog is active, but can be disabled
@@ -138,6 +138,7 @@ int __init check_nmi_watchdog(void) 
	if (!prev_nmi_count)

		goto error;



	alloc_cpumask_var(&backtrace_mask, GFP_KERNEL);

	printk(KERN_INFO "Testing NMI watchdog ... ");



#ifdef CONFIG_SMP
@@ -413,14 +414,14 @@ nmi_watchdog_tick(struct pt_regs *regs, unsigned reason) 
		touched = 1;

	}



	if (cpu_isset(cpu, backtrace_mask)) {

	if (cpumask_test_cpu(cpu, backtrace_mask)) {

		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */



		spin_lock(&lock);

		printk(KERN_WARNING "NMI backtrace for cpu %d\n", cpu);

		dump_stack();

		spin_unlock(&lock);

		cpu_clear(cpu, backtrace_mask);

		cpumask_clear_cpu(cpu, backtrace_mask);

	}



	/* Could check oops_in_progress here too, but it's safer not to */
@@ -554,10 +555,10 @@ void __trigger_all_cpu_backtrace(void) 
{

	int i;



	backtrace_mask = cpu_online_map;

	cpumask_copy(backtrace_mask, cpu_online_mask);

	/* Wait for up to 10 seconds for all CPUs to do the backtrace */

	for (i = 0; i < 10 * 1000; i++) {

		if (cpus_empty(backtrace_mask))

		if (cpumask_empty(backtrace_mask))

			break;

		mdelay(1);

	}