1 /*
2  * lib/smp_processor_id.c
3  *
4  * DEBUG_PREEMPT variant of smp_processor_id().
5  */
6 #include <linux/module.h>
7 #include <linux/kallsyms.h>
8 #include <linux/sched.h>
9 
debug_smp_processor_id(void)10 notrace unsigned int debug_smp_processor_id(void)
11 {
12 	unsigned long preempt_count = preempt_count();
13 	int this_cpu = raw_smp_processor_id();
14 
15 	if (likely(preempt_count))
16 		goto out;
17 
18 	if (irqs_disabled())
19 		goto out;
20 
21 	/*
22 	 * Kernel threads bound to a single CPU can safely use
23 	 * smp_processor_id():
24 	 */
25 	if (cpumask_equal(&current->cpus_allowed, cpumask_of(this_cpu)))
26 		goto out;
27 
28 	/*
29 	 * It is valid to assume CPU-locality during early bootup:
30 	 */
31 	if (system_state != SYSTEM_RUNNING)
32 		goto out;
33 
34 	/*
35 	 * Avoid recursion:
36 	 */
37 	preempt_disable_notrace();
38 
39 	if (!printk_ratelimit())
40 		goto out_enable;
41 
42 	printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] "
43 			"code: %s/%d\n",
44 			preempt_count() - 1, current->comm, current->pid);
45 	print_symbol("caller is %s\n", (long)__builtin_return_address(0));
46 	dump_stack();
47 
48 out_enable:
49 	preempt_enable_no_resched_notrace();
50 out:
51 	return this_cpu;
52 }
53 
54 EXPORT_SYMBOL(debug_smp_processor_id);
55 
56