powerpc/math/fpu_preempt.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * Copyright 2015, Cyril Bur, IBM Corp.
0004  *
0005  * This test attempts to see if the FPU registers change across preemption.
0006  * Two things should be noted here a) The check_fpu function in asm only checks
0007  * the non volatile registers as it is reused from the syscall test b) There is
0008  * no way to be sure preemption happened so this test just uses many threads
0009  * and a long wait. As such, a successful test doesn't mean much but a failure
0010  * is bad.
0011  */
0012
0013 #include <stdio.h>
0014 #include <unistd.h>
0015 #include <sys/syscall.h>
0016 #include <sys/time.h>
0017 #include <sys/types.h>
0018 #include <sys/wait.h>
0019 #include <stdlib.h>
0020 #include <pthread.h>
0021
0022 #include "utils.h"
0023
0024 /* Time to wait for workers to get preempted (seconds) */
0025 #define PREEMPT_TIME 20
0026 /*
0027  * Factor by which to multiply number of online CPUs for total number of
0028  * worker threads
0029  */
0030 #define THREAD_FACTOR 8
0031
0032
0033 __thread double darray[] = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0,
0034              1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,
0035              2.1};
0036
0037 int threads_starting;
0038 int running;
0039
0040 extern void preempt_fpu(double *darray, int *threads_starting, int *running);
0041
0042 void *preempt_fpu_c(void *p)
0043 {
0044     int i;
0045     srand(pthread_self());
0046     for (i = 0; i < 21; i++)
0047         darray[i] = rand();
0048
0049     /* Test failed if it ever returns */
0050     preempt_fpu(darray, &threads_starting, &running);
0051
0052     return p;
0053 }
0054
0055 int test_preempt_fpu(void)
0056 {
0057     int i, rc, threads;
0058     pthread_t *tids;
0059
0060     threads = sysconf(_SC_NPROCESSORS_ONLN) * THREAD_FACTOR;
0061     tids = malloc((threads) * sizeof(pthread_t));
0062     FAIL_IF(!tids);
0063
0064     running = true;
0065     threads_starting = threads;
0066     for (i = 0; i < threads; i++) {
0067         rc = pthread_create(&tids[i], NULL, preempt_fpu_c, NULL);
0068         FAIL_IF(rc);
0069     }
0070
0071     setbuf(stdout, NULL);
0072     /* Not really necessary but nice to wait for every thread to start */
0073     printf("\tWaiting for all workers to start...");
0074     while(threads_starting)
0075         asm volatile("": : :"memory");
0076     printf("done\n");
0077
0078     printf("\tWaiting for %d seconds to let some workers get preempted...", PREEMPT_TIME);
0079     sleep(PREEMPT_TIME);
0080     printf("done\n");
0081
0082     printf("\tStopping workers...");
0083     /*
0084      * Working are checking this value every loop. In preempt_fpu 'cmpwi r5,0; bne 2b'.
0085      * r5 will have loaded the value of running.
0086      */
0087     running = 0;
0088     for (i = 0; i < threads; i++) {
0089         void *rc_p;
0090         pthread_join(tids[i], &rc_p);
0091
0092         /*
0093          * Harness will say the fail was here, look at why preempt_fpu
0094          * returned
0095          */
0096         if ((long) rc_p)
0097             printf("oops\n");
0098         FAIL_IF((long) rc_p);
0099     }
0100     printf("done\n");
0101
0102     free(tids);
0103     return 0;
0104 }
0105
0106 int main(int argc, char *argv[])
0107 {
0108     return test_harness(test_preempt_fpu, "fpu_preempt");
0109 }