lib/smp_processor_id.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * lib/smp_processor_id.c
   4  *
   5  * DEBUG_PREEMPT variant of smp_processor_id().
   6  */
   7 #include <linux/export.h>
   8 #include <linux/sched.h>
   9
  10 notrace static unsigned int check_preemption_disabled(const char *what1,
  11                                                         const char *what2)
  12 {
  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_SCHEDULING)
  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 %s%s() in preemptible [%08x] code: %s/%d\n",
  43                 what1, what2, preempt_count() - 1, current->comm, current->pid);
  44
  45         printk("caller is %pS\n", __builtin_return_address(0));
  46         dump_stack();
  47
  48 out_enable:
  49         preempt_enable_no_resched_notrace();
  50 out:
  51         return this_cpu;
  52 }
  53
  54 notrace unsigned int debug_smp_processor_id(void)
  55 {
  56         return check_preemption_disabled("smp_processor_id", "");
  57 }
  58 EXPORT_SYMBOL(debug_smp_processor_id);
  59
  60 notrace void __this_cpu_preempt_check(const char *op)
  61 {
  62         check_preemption_disabled("__this_cpu_", op);
  63 }
  64 EXPORT_SYMBOL(__this_cpu_preempt_check);