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