LXR linux/lib/smp_processor

   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
  10unsigned 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();
  41
  42        if (!printk_ratelimit())
  43                goto out_enable;
  44
  45        printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] code: %s/%d\n", preempt_count(), current->comm, current->pid);
  46        print_symbol("caller is %s\n", (long)__builtin_return_address(0));
  47        dump_stack();
  48
  49out_enable:
  50        preempt_enable_no_resched();
  51out:
  52        return this_cpu;
  53}
  54
  55EXPORT_SYMBOL(debug_smp_processor_id);
  56
  57