ftrace: debug smp_processor_id, use notrace preempt disable
[linux-3.10.git] / lib / smp_processor_id.c
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
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         cpumask_t this_mask;
15
16         if (likely(preempt_count))
17                 goto out;
18
19         if (irqs_disabled())
20                 goto out;
21
22         /*
23          * Kernel threads bound to a single CPU can safely use
24          * smp_processor_id():
25          */
26         this_mask = cpumask_of_cpu(this_cpu);
27
28         if (cpus_equal(current->cpus_allowed, this_mask))
29                 goto out;
30
31         /*
32          * It is valid to assume CPU-locality during early bootup:
33          */
34         if (system_state != SYSTEM_RUNNING)
35                 goto out;
36
37         /*
38          * Avoid recursion:
39          */
40         preempt_disable_notrace();
41
42         if (!printk_ratelimit())
43                 goto out_enable;
44
45         printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] "
46                         "code: %s/%d\n",
47                         preempt_count() - 1, current->comm, current->pid);
48         print_symbol("caller is %s\n", (long)__builtin_return_address(0));
49         dump_stack();
50
51 out_enable:
52         preempt_enable_no_resched_notrace();
53 out:
54         return this_cpu;
55 }
56
57 EXPORT_SYMBOL(debug_smp_processor_id);
58