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

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