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_s390x_linux 33 34 #if defined(__APPLE__) && defined(__i386__) 35 # define PLAT_x86_darwin 1 36 #elif defined(__APPLE__) && defined(__x86_64__) 37 # define PLAT_amd64_darwin 1 38 #elif defined(__linux__) && defined(__i386__) 39 # define PLAT_x86_linux 1 40 #elif defined(__linux__) && defined(__x86_64__) 41 # define PLAT_amd64_linux 1 42 #elif defined(__linux__) && defined(__powerpc__) && !defined(__powerpc64__) 43 # define PLAT_ppc32_linux 1 44 #elif defined(__linux__) && defined(__powerpc__) && defined(__powerpc64__) 45 # define PLAT_ppc64_linux 1 46 #elif defined(__linux__) && defined(__arm__) 47 # define PLAT_arm_linux 1 48 #elif defined(__linux__) && defined(__s390x__) 49 # define PLAT_s390x_linux 1 50 #endif 51 52 53 #if defined(PLAT_amd64_linux) || defined(PLAT_x86_linux) \ 54 || defined(PLAT_amd64_darwin) || defined(PLAT_x86_darwin) 55 # define INC(_lval,_lqual) \ 56 __asm__ __volatile__ ( \ 57 "lock ; incl (%0)" : /*out*/ : /*in*/"r"(&(_lval)) : "memory", "cc" ) 58 #elif defined(PLAT_ppc32_linux) || defined(PLAT_ppc64_linux) 59 # define INC(_lval,_lqual) \ 60 __asm__ __volatile__( \ 61 "1:\n" \ 62 " lwarx 15,0,%0\n" \ 63 " addi 15,15,1\n" \ 64 " stwcx. 15,0,%0\n" \ 65 " bne- 1b\n" \ 66 : /*out*/ : /*in*/ "b"(&(_lval)) \ 67 : /*trash*/ "r15", "cr0", "memory" \ 68 ) 69 #elif defined(PLAT_arm_linux) 70 # define INC(_lval,_lqual) \ 71 __asm__ __volatile__( \ 72 "1:\n" \ 73 " ldrex r8, [%0, #0]\n" \ 74 " add r8, r8, #1\n" \ 75 " strex r9, r8, [%0, #0]\n" \ 76 " cmp r9, #0\n" \ 77 " bne 1b\n" \ 78 : /*out*/ : /*in*/ "r"(&(_lval)) \ 79 : /*trash*/ "r8", "r9", "cc", "memory" \ 80 ); 81 #elif defined(PLAT_s390x_linux) 82 # define INC(_lval,_lqual) \ 83 __asm__ __volatile__( \ 84 "1: l 0,%0\n" \ 85 " lr 1,0\n" \ 86 " ahi 1,1\n" \ 87 " cs 0,1,%0\n" \ 88 " jl 1b\n" \ 89 : "+m" (_lval) :: "cc", "0","1" \ 90 ) 91 #else 92 # error "Fix Me for this platform" 93 #endif 94 95 96 97 #define LIMIT 10 98 99 volatile int x = 0; 100 101 void* child_fn ( void* arg ) 102 { 103 int q = 0; 104 int oldx = 0; 105 struct timespec ts = { 0, 1000 * 1000 }; 106 107 while (1) { 108 q = (x >= LIMIT); 109 if (x != oldx) { 110 oldx = x; 111 printf("child: new value %d\n", oldx); 112 fflush(stdout); 113 } 114 if (q) break; 115 nanosleep(&ts, 0); 116 } 117 return NULL; 118 } 119 120 int main ( void ) 121 { 122 pthread_t child; 123 int i; 124 125 if (pthread_create(&child, NULL, child_fn, NULL)) { 126 perror("pthread_create"); 127 exit(1); 128 } 129 130 for (i = 0; i < LIMIT; i++) { 131 INC(x, "main"); 132 if (i == 5) sleep(1); /* make sure child doesn't starve */ 133 } 134 135 if (pthread_join(child, NULL)) { 136 perror("pthread join"); 137 exit(1); 138 } 139 140 printf("done, x = %d\n", x); 141 142 return 0; 143 } 144
