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/kprobes.h>
   9 #include <linux/sched.h>
  10
  11 noinstr static
  12 unsigned int check_preemption_disabled(const char *what1, const char *what2)
  13 {
  14         int this_cpu = raw_smp_processor_id();
  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         if (current->nr_cpus_allowed == 1)
  27                 goto out;
  28
  29 #ifdef CONFIG_SMP
  30         if (current->migration_disabled)
  31                 goto out;
  32 #endif
  33
  34         /*
  35          * It is valid to assume CPU-locality during early bootup:
  36          */
  37         if (system_state < SYSTEM_SCHEDULING)
  38                 goto out;
  39
  40         /*
  41          * Avoid recursion:
  42          */
  43         preempt_disable_notrace();
  44
  45         instrumentation_begin();
  46         if (!printk_ratelimit())
  47                 goto out_enable;
  48
  49         printk(KERN_ERR "BUG: using %s%s() in preemptible [%08x] code: %s/%d\n",
  50                 what1, what2, preempt_count() - 1, current->comm, current->pid);
  51
  52         printk("caller is %pS\n", __builtin_return_address(0));
  53         dump_stack();
  54         instrumentation_end();
  55
  56 out_enable:
  57         preempt_enable_no_resched_notrace();
  58 out:
  59         return this_cpu;
  60 }
  61
  62 noinstr unsigned int debug_smp_processor_id(void)
  63 {
  64         return check_preemption_disabled("smp_processor_id", "");
  65 }
  66 EXPORT_SYMBOL(debug_smp_processor_id);
  67
  68 noinstr void __this_cpu_preempt_check(const char *op)
  69 {
  70         check_preemption_disabled("__this_cpu_", op);
  71 }
  72 EXPORT_SYMBOL(__this_cpu_preempt_check);