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
preempt_fpu_c(void * p)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
test_preempt_fpu(void)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
main(int argc,char * argv[])102 int main(int argc, char *argv[])
103 {
104 return test_harness(test_preempt_fpu, "fpu_preempt");
105 }
106