vsx_preempt.c

  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 VSX registers change across preemption.
  6 * There is no way to be sure preemption happened so this test just
  7 * uses many threads and a long wait. As such, a successful test
  8 * doesn't mean much but a failure is bad.
  9 */
 10
 11#include <stdio.h>
 12#include <string.h>
 13#include <unistd.h>
 14#include <sys/syscall.h>
 15#include <sys/time.h>
 16#include <sys/types.h>
 17#include <sys/wait.h>
 18#include <stdlib.h>
 19#include <pthread.h>
 20
 21#include "utils.h"
 22
 23/* Time to wait for workers to get preempted (seconds) */
 24#define PREEMPT_TIME 20
 25/*
 26 * Factor by which to multiply number of online CPUs for total number of
 27 * worker threads
 28 */
 29#define THREAD_FACTOR 8
 30
 31/*
 32 * Ensure there is twice the number of non-volatile VMX regs!
 33 * check_vmx() is going to use the other half as space to put the live
 34 * registers before calling vsx_memcmp()
 35 */
 36__thread vector int varray[24] = {
 37	{1, 2, 3, 4 }, {5, 6, 7, 8 }, {9, 10,11,12},
 38	{13,14,15,16}, {17,18,19,20}, {21,22,23,24},
 39	{25,26,27,28}, {29,30,31,32}, {33,34,35,36},
 40	{37,38,39,40}, {41,42,43,44}, {45,46,47,48}
 41};
 42
 43int threads_starting;
 44int running;
 45
 46extern long preempt_vsx(vector int *varray, int *threads_starting, int *running);
 47
 48long vsx_memcmp(vector int *a) {
 49	vector int zero = {0, 0, 0, 0};
 50	int i;
 51
 52	FAIL_IF(a != varray);
 53
 54	for(i = 0; i < 12; i++) {
 55		if (memcmp(&a[i + 12], &zero, sizeof(vector int)) == 0) {
 56			fprintf(stderr, "Detected zero from the VSX reg %d\n", i + 12);
 57			return 2;
 58		}
 59	}
 60
 61	if (memcmp(a, &a[12], 12 * sizeof(vector int))) {
 62		long *p = (long *)a;
 63		fprintf(stderr, "VSX mismatch\n");
 64		for (i = 0; i < 24; i=i+2)
 65			fprintf(stderr, "%d: 0x%08lx%08lx | 0x%08lx%08lx\n",
 66					i/2 + i%2 + 20, p[i], p[i + 1], p[i + 24], p[i + 25]);
 67		return 1;
 68	}
 69	return 0;
 70}
 71
 72void *preempt_vsx_c(void *p)
 73{
 74	int i, j;
 75	long rc;
 76	srand(pthread_self());
 77	for (i = 0; i < 12; i++)
 78		for (j = 0; j < 4; j++) {
 79			varray[i][j] = rand();
 80			/* Don't want zero because it hides kernel problems */
 81			if (varray[i][j] == 0)
 82				j--;
 83		}
 84	rc = preempt_vsx(varray, &threads_starting, &running);
 85	if (rc == 2)
 86		fprintf(stderr, "Caught zeros in VSX compares\n");
 87	return (void *)rc;
 88}
 89
 90int test_preempt_vsx(void)
 91{
 92	int i, rc, threads;
 93	pthread_t *tids;
 94
 95	SKIP_IF(!have_hwcap(PPC_FEATURE_HAS_VSX));
 96
 97	threads = sysconf(_SC_NPROCESSORS_ONLN) * THREAD_FACTOR;
 98	tids = malloc(threads * sizeof(pthread_t));
 99	FAIL_IF(!tids);
100
101	running = true;
102	threads_starting = threads;
103	for (i = 0; i < threads; i++) {
104		rc = pthread_create(&tids[i], NULL, preempt_vsx_c, NULL);
105		FAIL_IF(rc);
106	}
107
108	setbuf(stdout, NULL);
109	/* Not really nessesary but nice to wait for every thread to start */
110	printf("\tWaiting for %d workers to start...", threads_starting);
111	while(threads_starting)
112		asm volatile("": : :"memory");
113	printf("done\n");
114
115	printf("\tWaiting for %d seconds to let some workers get preempted...", PREEMPT_TIME);
116	sleep(PREEMPT_TIME);
117	printf("done\n");
118
119	printf("\tStopping workers...");
120	/*
121	 * Working are checking this value every loop. In preempt_vsx 'cmpwi r5,0; bne 2b'.
122	 * r5 will have loaded the value of running.
123	 */
124	running = 0;
125	for (i = 0; i < threads; i++) {
126		void *rc_p;
127		pthread_join(tids[i], &rc_p);
128
129		/*
130		 * Harness will say the fail was here, look at why preempt_vsx
131		 * returned
132		 */
133		if ((long) rc_p)
134			printf("oops\n");
135		FAIL_IF((long) rc_p);
136	}
137	printf("done\n");
138
139	return 0;
140}
141
142int main(int argc, char *argv[])
143{
144	return test_harness(test_preempt_vsx, "vsx_preempt");
145}