tests/kernel/rdtsc-smp.c

   1 /* rdtsc-smp
   2  *
   3  * Test TSC
   4  */
   5
   6
   7 #include <linux/jiffies.h>
   8 #include <linux/compiler.h>
   9 #include <linux/init.h>
  10 #include <linux/module.h>
  11 #include <linux/workqueue.h>
  12
  13 static atomic_t busy_wait;
  14 static struct delayed_work testwork[NR_CPUS];
  15
  16
  17 static void do_work(struct work_struct *work)
  18 {
  19         cycles_t val;
  20         int cpu1, cpu2;
  21         int num_online = num_online_cpus();
  22         int copybusy;
  23         int i;
  24
  25         cpu1 = smp_processor_id();
  26         printk("Busy waiting on cpu %d\n", cpu1);
  27
  28         /* Prime busy_wait in cache */
  29         for(i=0; i<100; i++) {
  30                 copybusy = atomic_read(&busy_wait);
  31         }
  32         barrier();
  33         atomic_inc(&busy_wait);
  34         while(atomic_read(&busy_wait) != num_online) {
  35                 barrier();
  36         }
  37
  38         val = get_cycles();
  39
  40         cpu2 = smp_processor_id();
  41         BUG_ON(cpu1 != cpu2);
  42         printk("Cycle count on cpu %d is %llu\n", cpu1, val);
  43 }
  44
  45
  46 static int ltt_test_init(void)
  47 {
  48         int cpu;
  49
  50         printk(KERN_ALERT "test init\n");
  51
  52         atomic_set(&busy_wait, 0);
  53         for_each_online_cpu(cpu) {
  54                 INIT_DELAYED_WORK(&testwork[cpu], do_work);
  55                 schedule_delayed_work_on(cpu, &testwork[cpu], 0);
  56         }
  57         return 0;
  58 }
  59
  60 static void ltt_test_exit(void)
  61 {
  62         /* Test program... wait for output before unload */
  63         printk(KERN_ALERT "test exit\n");
  64 }
  65
  66 module_init(ltt_test_init)
  67 module_exit(ltt_test_exit)
  68
  69 MODULE_LICENSE("GPL");
  70 MODULE_AUTHOR("Mathieu Desnoyers");
  71 MODULE_DESCRIPTION("Linux Trace Toolkit Test");
  72