/*
   * lib/smp_processor_id.c
   *
   * DEBUG_PREEMPT variant of smp_processor_id().
   */
  #include <linux/module.h>
  #include <linux/kallsyms.h>

  #include <linux/sched.h>

  
  unsigned int debug_smp_processor_id(void)
  {
  	unsigned long preempt_count = preempt_count();
  	int this_cpu = raw_smp_processor_id();
  	cpumask_t this_mask;
  
  	if (likely(preempt_count))
  		goto out;
  
  	if (irqs_disabled())
  		goto out;
  
  	/*
  	 * Kernel threads bound to a single CPU can safely use
  	 * smp_processor_id():
  	 */
  	this_mask = cpumask_of_cpu(this_cpu);
  
  	if (cpus_equal(current->cpus_allowed, this_mask))
  		goto out;
  
  	/*
  	 * It is valid to assume CPU-locality during early bootup:
  	 */
  	if (system_state != SYSTEM_RUNNING)
  		goto out;
  
  	/*
  	 * Avoid recursion:
  	 */
  	preempt_disable();
  
  	if (!printk_ratelimit())
  		goto out_enable;

  	printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] "
  			"code: %s/%d
  ",
  			preempt_count() - 1, current->comm, current->pid);

  	print_symbol("caller is %s
  ", (long)__builtin_return_address(0));
  	dump_stack();
  
  out_enable:
  	preempt_enable_no_resched();
  out:
  	return this_cpu;
  }
  
  EXPORT_SYMBOL(debug_smp_processor_id);