1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * POWER Data Stream Control Register (DSCR) default test
4  *
5  * This test modifies the system wide default DSCR through
6  * it's sysfs interface and then verifies that all threads
7  * see the correct changed DSCR value immediately.
8  *
9  * Copyright 2012, Anton Blanchard, IBM Corporation.
10  * Copyright 2015, Anshuman Khandual, IBM Corporation.
11  */
12 #include "dscr.h"
13 
14 static unsigned long dscr;		/* System DSCR default */
15 static unsigned long sequence;
16 static unsigned long result[THREADS];
17 
18 static void *do_test(void *in)
19 {
20 	unsigned long thread = (unsigned long)in;
21 	unsigned long i;
22 
23 	for (i = 0; i < COUNT; i++) {
24 		unsigned long d, cur_dscr, cur_dscr_usr;
25 		unsigned long s1, s2;
26 
27 		s1 = READ_ONCE(sequence);
28 		if (s1 & 1)
29 			continue;
30 		rmb();
31 
32 		d = dscr;
33 		cur_dscr = get_dscr();
34 		cur_dscr_usr = get_dscr_usr();
35 
36 		rmb();
37 		s2 = sequence;
38 
39 		if (s1 != s2)
40 			continue;
41 
42 		if (cur_dscr != d) {
43 			fprintf(stderr, "thread %ld kernel DSCR should be %ld "
44 				"but is %ld\n", thread, d, cur_dscr);
45 			result[thread] = 1;
46 			pthread_exit(&result[thread]);
47 		}
48 
49 		if (cur_dscr_usr != d) {
50 			fprintf(stderr, "thread %ld user DSCR should be %ld "
51 				"but is %ld\n", thread, d, cur_dscr_usr);
52 			result[thread] = 1;
53 			pthread_exit(&result[thread]);
54 		}
55 	}
56 	result[thread] = 0;
57 	pthread_exit(&result[thread]);
58 }
59 
60 int dscr_default(void)
61 {
62 	pthread_t threads[THREADS];
63 	unsigned long i, *status[THREADS];
64 	unsigned long orig_dscr_default;
65 
66 	SKIP_IF(!have_hwcap2(PPC_FEATURE2_DSCR));
67 
68 	orig_dscr_default = get_default_dscr();
69 
70 	/* Initial DSCR default */
71 	dscr = 1;
72 	set_default_dscr(dscr);
73 
74 	/* Spawn all testing threads */
75 	for (i = 0; i < THREADS; i++) {
76 		if (pthread_create(&threads[i], NULL, do_test, (void *)i)) {
77 			perror("pthread_create() failed");
78 			goto fail;
79 		}
80 	}
81 
82 	srand(getpid());
83 
84 	/* Keep changing the DSCR default */
85 	for (i = 0; i < COUNT; i++) {
86 		double ret = uniform_deviate(rand());
87 
88 		if (ret < 0.0001) {
89 			sequence++;
90 			wmb();
91 
92 			dscr++;
93 			if (dscr > DSCR_MAX)
94 				dscr = 0;
95 
96 			set_default_dscr(dscr);
97 
98 			wmb();
99 			sequence++;
100 		}
101 	}
102 
103 	/* Individual testing thread exit status */
104 	for (i = 0; i < THREADS; i++) {
105 		if (pthread_join(threads[i], (void **)&(status[i]))) {
106 			perror("pthread_join() failed");
107 			goto fail;
108 		}
109 
110 		if (*status[i]) {
111 			printf("%ldth thread failed to join with %ld status\n",
112 								i, *status[i]);
113 			goto fail;
114 		}
115 	}
116 	set_default_dscr(orig_dscr_default);
117 	return 0;
118 fail:
119 	set_default_dscr(orig_dscr_default);
120 	return 1;
121 }
122 
123 int main(int argc, char *argv[])
124 {
125 	return test_harness(dscr_default, "dscr_default_test");
126 }
127