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 
preempt_fpu_c(void * p)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 
test_preempt_fpu(void)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 
main(int argc,char * argv[])106 int main(int argc, char *argv[])
107 {
108 	return test_harness(test_preempt_fpu, "fpu_preempt");
109 }
110