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

DEFINITIONS

1. preempt_fpu_c
2. test_preempt_fpu
3. main

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