1
2 /* FIXME: this is basically a bad test as it is scheduling-
3 sensitive. Sometimes the output is:
4
5 child: new value 6
6 child: new value 10
7 done, x = 10
8
9 and sometimes
10
11 child: new value 10
12 done, x = 10
13 */
14
15 #include <pthread.h>
16 #include <stdio.h>
17 #include <stdlib.h>
18 #include <unistd.h>
19
20 /* Simple test program, no race. Parent writes atomically to a counter
21 whilst child reads it. When counter reaches a prearranged value,
22 child joins back to parent. Parent (writer) uses hardware bus lock;
23 child is only reading and so does not need to use a bus lock. */
24
25 #undef PLAT_x86_darwin
26 #undef PLAT_amd64_darwin
27 #undef PLAT_x86_linux
28 #undef PLAT_amd64_linux
29 #undef PLAT_ppc32_linux
30 #undef PLAT_ppc64_linux
31 #undef PLAT_arm_linux
32 #undef PLAT_arm64_linux
33 #undef PLAT_s390x_linux
34 #undef PLAT_mips32_linux
35 #undef PLAT_mips64_linux
36
37 #if defined(__APPLE__) && defined(__i386__)
38 # define PLAT_x86_darwin 1
39 #elif defined(__APPLE__) && defined(__x86_64__)
40 # define PLAT_amd64_darwin 1
41 #elif defined(__linux__) && defined(__i386__)
42 # define PLAT_x86_linux 1
43 #elif defined(__linux__) && defined(__x86_64__)
44 # define PLAT_amd64_linux 1
45 #elif defined(__linux__) && defined(__powerpc__) && !defined(__powerpc64__)
46 # define PLAT_ppc32_linux 1
47 #elif defined(__linux__) && defined(__powerpc__) && defined(__powerpc64__)
48 # define PLAT_ppc64_linux 1
49 #elif defined(__linux__) && defined(__arm__) && !defined(__aarch64__)
50 # define PLAT_arm_linux 1
51 #elif defined(__linux__) && defined(__aarch64__) && !defined(__arm__)
52 # define PLAT_arm64_linux 1
53 #elif defined(__linux__) && defined(__s390x__)
54 # define PLAT_s390x_linux 1
55 #elif defined(__linux__) && defined(__mips__)
56 #if (__mips==64)
57 # define PLAT_mips64_linux 1
58 #else
59 # define PLAT_mips32_linux 1
60 #endif
61 #endif
62
63
64 #if defined(PLAT_amd64_linux) || defined(PLAT_x86_linux) \
65 || defined(PLAT_amd64_darwin) || defined(PLAT_x86_darwin)
66 # define INC(_lval,_lqual) \
67 __asm__ __volatile__ ( \
68 "lock ; incl (%0)" : /*out*/ : /*in*/"r"(&(_lval)) : "memory", "cc" )
69 #elif defined(PLAT_ppc32_linux) || defined(PLAT_ppc64_linux)
70 # define INC(_lval,_lqual) \
71 __asm__ __volatile__( \
72 "1:\n" \
73 " lwarx 15,0,%0\n" \
74 " addi 15,15,1\n" \
75 " stwcx. 15,0,%0\n" \
76 " bne- 1b\n" \
77 : /*out*/ : /*in*/ "b"(&(_lval)) \
78 : /*trash*/ "r15", "cr0", "memory" \
79 )
80 #elif defined(PLAT_arm_linux)
81 # define INC(_lval,_lqual) \
82 __asm__ __volatile__( \
83 "1:\n" \
84 " ldrex r8, [%0, #0]\n" \
85 " add r8, r8, #1\n" \
86 " strex r9, r8, [%0, #0]\n" \
87 " cmp r9, #0\n" \
88 " bne 1b\n" \
89 : /*out*/ : /*in*/ "r"(&(_lval)) \
90 : /*trash*/ "r8", "r9", "cc", "memory" \
91 );
92 #elif defined(PLAT_arm64_linux)
93 # define INC(_lval,_lqual) \
94 __asm__ __volatile__( \
95 "1:\n" \
96 " ldxr w8, [%0, #0]\n" \
97 " add w8, w8, #1\n" \
98 " stxr w9, w8, [%0, #0]\n" \
99 " cmp w9, #0\n" \
100 " bne 1b\n" \
101 : /*out*/ : /*in*/ "r"(&(_lval)) \
102 : /*trash*/ "x8", "x9", "cc", "memory" \
103 );
104 #elif defined(PLAT_s390x_linux)
105 # define INC(_lval,_lqual) \
106 __asm__ __volatile__( \
107 "1: l 0,%0\n" \
108 " lr 1,0\n" \
109 " ahi 1,1\n" \
110 " cs 0,1,%0\n" \
111 " jl 1b\n" \
112 : "+m" (_lval) :: "cc", "0","1" \
113 )
114 #elif defined(PLAT_mips32_linux) || defined(PLAT_mips64_linux)
115 # define INC(_lval,_lqual) \
116 __asm__ __volatile__ ( \
117 "L1xyzzy1" _lqual":\n" \
118 " move $t0, %0\n" \
119 " ll $t1, 0($t0)\n" \
120 " addi $t1, $t1, 1\n" \
121 " sc $t1, 0($t0)\n" \
122 " beqz $t1, L1xyzzy1" _lqual \
123 : /*out*/ : /*in*/ "r"(&(_lval)) \
124 : /*trash*/ "t0", "t1", "memory" \
125 )
126 #else
127 # error "Fix Me for this platform"
128 #endif
129
130
131
132 #define LIMIT 10
133
134 volatile int x = 0;
135
child_fn(void * arg)136 void* child_fn ( void* arg )
137 {
138 int q = 0;
139 int oldx = 0;
140 struct timespec ts = { 0, 1000 * 1000 };
141
142 while (1) {
143 q = (x >= LIMIT);
144 if (x != oldx) {
145 oldx = x;
146 printf("child: new value %d\n", oldx);
147 fflush(stdout);
148 }
149 if (q) break;
150 nanosleep(&ts, 0);
151 }
152 return NULL;
153 }
154
main(void)155 int main ( void )
156 {
157 pthread_t child;
158 int i;
159
160 if (pthread_create(&child, NULL, child_fn, NULL)) {
161 perror("pthread_create");
162 exit(1);
163 }
164
165 for (i = 0; i < LIMIT; i++) {
166 INC(x, "main");
167 if (i == 5) sleep(1); /* make sure child doesn't starve */
168 }
169
170 if (pthread_join(child, NULL)) {
171 perror("pthread join");
172 exit(1);
173 }
174
175 printf("done, x = %d\n", x);
176
177 return 0;
178 }
179