Root/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
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
56

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