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
10notrace 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
48out_enable:
49	preempt_enable_no_resched_notrace();
50out:
51	return this_cpu;
52}
53
54EXPORT_SYMBOL(debug_smp_processor_id);
55