tools/testing/selftests/powerpc/math/fpu_preempt.c

   1 /*
   2  * Copyright 2015, Cyril Bur, IBM Corp.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version
   7  * 2 of the License, or (at your option) any later version.
   8  *
   9  * This test attempts to see if the FPU registers change across preemption.
  10  * Two things should be noted here a) The check_fpu function in asm only checks
  11  * the non volatile registers as it is reused from the syscall test b) There is
  12  * no way to be sure preemption happened so this test just uses many threads
  13  * and a long wait. As such, a successful test doesn't mean much but a failure
  14  * is bad.
  15  */
  16
  17 #include <stdio.h>
  18 #include <unistd.h>
  19 #include <sys/syscall.h>
  20 #include <sys/time.h>
  21 #include <sys/types.h>
  22 #include <sys/wait.h>
  23 #include <stdlib.h>
  24 #include <pthread.h>
  25
  26 #include "utils.h"
  27
  28 /* Time to wait for workers to get preempted (seconds) */
  29 #define PREEMPT_TIME 20
  30 /*
  31  * Factor by which to multiply number of online CPUs for total number of
  32  * worker threads
  33  */
  34 #define THREAD_FACTOR 8
  35
  36
  37 __thread double darray[] = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0,
  38                      1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,
  39                      2.1};
  40
  41 int threads_starting;
  42 int running;
  43
  44 extern void preempt_fpu(double *darray, int *threads_starting, int *running);
  45
  46 void *preempt_fpu_c(void *p)
  47 {
  48         int i;
  49         srand(pthread_self());
  50         for (i = 0; i < 21; i++)
  51                 darray[i] = rand();
  52
  53         /* Test failed if it ever returns */
  54         preempt_fpu(darray, &threads_starting, &running);
  55
  56         return p;
  57 }
  58
  59 int test_preempt_fpu(void)
  60 {
  61         int i, rc, threads;
  62         pthread_t *tids;
  63
  64         threads = sysconf(_SC_NPROCESSORS_ONLN) * THREAD_FACTOR;
  65         tids = malloc((threads) * sizeof(pthread_t));
  66         FAIL_IF(!tids);
  67
  68         running = true;
  69         threads_starting = threads;
  70         for (i = 0; i < threads; i++) {
  71                 rc = pthread_create(&tids[i], NULL, preempt_fpu_c, NULL);
  72                 FAIL_IF(rc);
  73         }
  74
  75         setbuf(stdout, NULL);
  76         /* Not really necessary but nice to wait for every thread to start */
  77         printf("\tWaiting for all workers to start...");
  78         while(threads_starting)
  79                 asm volatile("": : :"memory");
  80         printf("done\n");
  81
  82         printf("\tWaiting for %d seconds to let some workers get preempted...", PREEMPT_TIME);
  83         sleep(PREEMPT_TIME);
  84         printf("done\n");
  85
  86         printf("\tStopping workers...");
  87         /*
  88          * Working are checking this value every loop. In preempt_fpu 'cmpwi r5,0; bne 2b'.
  89          * r5 will have loaded the value of running.
  90          */
  91         running = 0;
  92         for (i = 0; i < threads; i++) {
  93                 void *rc_p;
  94                 pthread_join(tids[i], &rc_p);
  95
  96                 /*
  97                  * Harness will say the fail was here, look at why preempt_fpu
  98                  * returned
  99                  */
 100                 if ((long) rc_p)
 101                         printf("oops\n");
 102                 FAIL_IF((long) rc_p);
 103         }
 104         printf("done\n");
 105
 106         free(tids);
 107         return 0;
 108 }
 109
 110 int main(int argc, char *argv[])
 111 {
 112         return test_harness(test_preempt_fpu, "fpu_preempt");
 113 }