tests/kernel/test-local.c

   1 /* test-local.c
   2  *
   3  * Sample module for local.h usage.
   4  */
   5
   6
   7 #include <asm/local.h>
   8 #include <linux/module.h>
   9 #include <linux/timer.h>
  10
  11 static DEFINE_PER_CPU(local_t, counters) = LOCAL_INIT(0);
  12
  13 static struct timer_list test_timer;
  14
  15 /* IPI called on each CPU. */
  16 static void test_each(void *info)
  17 {
  18         /* Increment the counter from a non preemptible context */
  19         printk("Increment on cpu %d\n", smp_processor_id());
  20         local_inc(&__get_cpu_var(counters));
  21
  22         /* This is what incrementing the variable would look like within a
  23          * preemptible context (it disables preemption) :
  24          *
  25          * local_inc(&get_cpu_var(counters));
  26          * put_cpu_var(counters);
  27          */
  28 }
  29
  30 static void do_test_timer(unsigned long data)
  31 {
  32         int cpu;
  33
  34         /* Increment the counters */
  35         on_each_cpu(test_each, NULL, 0, 1);
  36         /* Read all the counters */
  37         printk("Counters read from CPU %d\n", smp_processor_id());
  38         for_each_online_cpu(cpu) {
  39                 printk("Read : CPU %d, count %ld\n", cpu,
  40                         local_read(&per_cpu(counters, cpu)));
  41         }
  42         del_timer(&test_timer);
  43         test_timer.expires = jiffies + 1000;
  44         add_timer(&test_timer);
  45 }
  46
  47 static int __init test_init(void)
  48 {
  49         /* initialize the timer that will increment the counter */
  50         init_timer(&test_timer);
  51         test_timer.function = do_test_timer;
  52         test_timer.expires = jiffies + 1;
  53         add_timer(&test_timer);
  54
  55         return 0;
  56 }
  57
  58 static void __exit test_exit(void)
  59 {
  60         del_timer_sync(&test_timer);
  61 }
  62
  63 module_init(test_init);
  64 module_exit(test_exit);
  65
  66 MODULE_LICENSE("GPL");
  67 MODULE_AUTHOR("Mathieu Desnoyers");
  68 MODULE_DESCRIPTION("Local Atomic Ops");
  69