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
   9 unsigned int debug_smp_processor_id(void)
  10 {
  11         unsigned long preempt_count = preempt_count();
  12         int this_cpu = raw_smp_processor_id();
  13         cpumask_t this_mask;
  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         this_mask = cpumask_of_cpu(this_cpu);
  26
  27         if (cpus_equal(current->cpus_allowed, this_mask))
  28                 goto out;
  29
  30         /*
  31          * It is valid to assume CPU-locality during early bootup:
  32          */
  33         if (system_state != SYSTEM_RUNNING)
  34                 goto out;
  35
  36         /*
  37          * Avoid recursion:
  38          */
  39         preempt_disable();
  40
  41         if (!printk_ratelimit())
  42                 goto out_enable;
  43
  44         printk(KERN_ERR "BUG: using smp_processor_id() in preemptible [%08x] code: %s/%d\n", preempt_count(), current->comm, current->pid);
  45         print_symbol("caller is %s\n", (long)__builtin_return_address(0));
  46         dump_stack();
  47
  48 out_enable:
  49         preempt_enable_no_resched();
  50 out:
  51         return this_cpu;
  52 }
  53
  54 EXPORT_SYMBOL(debug_smp_processor_id);
  55