1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2015, Cyril Bur, IBM Corp.
4  * Copyright 2023, Michael Ellerman, IBM Corp.
5  *
6  * This test attempts to see if the FPU registers change across preemption.
7  * There is no way to be sure preemption happened so this test just uses many
8  * threads and a long wait. As such, a successful test doesn't mean much but
9  * a failure is bad.
10  */
11 
12 #include <stdio.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 #include "fpu.h"
23 
24 /* Time to wait for workers to get preempted (seconds) */
25 #define PREEMPT_TIME 60
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[32];
34 
35 int threads_starting;
36 int running;
37 
38 extern int preempt_fpu(double *darray, int *threads_starting, int *running);
39 
40 void *preempt_fpu_c(void *p)
41 {
42 	long rc;
43 
44 	srand(pthread_self());
45 	randomise_darray(darray, ARRAY_SIZE(darray));
46 	rc = preempt_fpu(darray, &threads_starting, &running);
47 
48 	return (void *)rc;
49 }
50 
51 int test_preempt_fpu(void)
52 {
53 	int i, rc, threads;
54 	pthread_t *tids;
55 
56 	threads = sysconf(_SC_NPROCESSORS_ONLN) * THREAD_FACTOR;
57 	tids = malloc((threads) * sizeof(pthread_t));
58 	FAIL_IF(!tids);
59 
60 	running = true;
61 	threads_starting = threads;
62 	for (i = 0; i < threads; i++) {
63 		rc = pthread_create(&tids[i], NULL, preempt_fpu_c, NULL);
64 		FAIL_IF(rc);
65 	}
66 
67 	setbuf(stdout, NULL);
68 	/* Not really necessary but nice to wait for every thread to start */
69 	printf("\tWaiting for all workers to start...");
70 	while(threads_starting)
71 		asm volatile("": : :"memory");
72 	printf("done\n");
73 
74 	printf("\tWaiting for %d seconds to let some workers get preempted...", PREEMPT_TIME);
75 	sleep(PREEMPT_TIME);
76 	printf("done\n");
77 
78 	printf("\tStopping workers...");
79 	/*
80 	 * Working are checking this value every loop. In preempt_fpu 'cmpwi r5,0; bne 2b'.
81 	 * r5 will have loaded the value of running.
82 	 */
83 	running = 0;
84 	for (i = 0; i < threads; i++) {
85 		void *rc_p;
86 		pthread_join(tids[i], &rc_p);
87 
88 		/*
89 		 * Harness will say the fail was here, look at why preempt_fpu
90 		 * returned
91 		 */
92 		if ((long) rc_p)
93 			printf("oops\n");
94 		FAIL_IF((long) rc_p);
95 	}
96 	printf("done\n");
97 
98 	free(tids);
99 	return 0;
100 }
101 
102 int main(int argc, char *argv[])
103 {
104 	return test_harness(test_preempt_fpu, "fpu_preempt");
105 }
106