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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 | #include <semaphore.h> #include <sys/mman.h> #include <limits.h> #include <fcntl.h> #include <unistd.h> #include <string.h> #include <stdarg.h> #include <errno.h> #include <time.h> #include <stdio.h> #include <sys/stat.h> #include <stdlib.h> #include <pthread.h> static struct { ino_t ino; sem_t *sem; int refcnt; } *semtab; static int semcnt; static pthread_spinlock_t lock; static pthread_once_t once; static void init() { semtab = calloc(sizeof *semtab, SEM_NSEMS_MAX); } static sem_t *find_map(ino_t ino) { int i; for (i=0; i<SEM_NSEMS_MAX && semtab[i].ino != ino; i++); if (i==SEM_NSEMS_MAX) return 0; if (semtab[i].refcnt == INT_MAX) return (sem_t *)-1; semtab[i].refcnt++; return semtab[i].sem; } sem_t *sem_open(const char *name, int flags, ...) { va_list ap; mode_t mode; unsigned value; int fd, tfd, dir; sem_t newsem; void *map; char tmp[64]; struct timespec ts; struct stat st; int i; while (*name=='/') name++; if (strchr(name, '/')) { errno = EINVAL; return SEM_FAILED; } pthread_once(&once, init); if (!semtab) { errno = ENOMEM; return SEM_FAILED; } if (flags & O_CREAT) { va_start(ap, flags); mode = va_arg(ap, mode_t) & 0666; value = va_arg(ap, unsigned); va_end(ap); if (value > SEM_VALUE_MAX) { errno = EINVAL; return SEM_FAILED; } sem_init(&newsem, 0, value); clock_gettime(CLOCK_REALTIME, &ts); snprintf(tmp, sizeof(tmp), "/dev/shm/%p-%p-%d-%d", &name, name, (int)getpid(), (int)ts.tv_nsec); tfd = open(tmp, O_CREAT|O_EXCL|O_RDWR, mode); if (tfd<0) return SEM_FAILED; dir = open("/dev/shm", O_DIRECTORY|O_RDONLY); if (dir<0 || write(tfd,&newsem,sizeof newsem)!=sizeof newsem) { if (dir >= 0) close(dir); close(tfd); unlink(tmp); return SEM_FAILED; } } flags &= ~O_ACCMODE; flags |= O_RDWR; pthread_spin_lock(&lock); for (;;) { if (!(flags & O_EXCL)) { fd = shm_open(name, flags&~O_CREAT, mode); if (fd >= 0 || errno != ENOENT) { if (flags & O_CREAT) { close(dir); close(tfd); unlink(tmp); } if (fd >= 0 && fstat(fd, &st) < 0) { close(fd); fd = -1; } if (fd < 0) { pthread_spin_unlock(&lock); return SEM_FAILED; } if ((map = find_map(st.st_ino))) { pthread_spin_unlock(&lock); close(fd); if (map == (sem_t *)-1) return SEM_FAILED; return map; } break; } } if (!(flags & O_CREAT)) { pthread_spin_unlock(&lock); return SEM_FAILED; } if (!linkat(AT_FDCWD, tmp, dir, name, 0)) { fd = tfd; close(dir); unlink(tmp); break; } if ((flags & O_EXCL) || errno != EEXIST) { close(dir); close(tfd); unlink(tmp); return SEM_FAILED; } } if (fstat(fd, &st) < 0) { pthread_spin_unlock(&lock); close(fd); return SEM_FAILED; } if (semcnt == SEM_NSEMS_MAX) { pthread_spin_unlock(&lock); close(fd); errno = EMFILE; return SEM_FAILED; } for (i=0; i<SEM_NSEMS_MAX && semtab[i].sem; i++); map = mmap(0, sizeof(sem_t), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); close(fd); if (map == MAP_FAILED) { pthread_spin_unlock(&lock); return SEM_FAILED; } semtab[i].ino = st.st_ino; semtab[i].sem = map; semtab[i].refcnt = 1; pthread_spin_unlock(&lock); return map; } int sem_close(sem_t *sem) { int i; pthread_spin_lock(&lock); for (i=0; i<SEM_NSEMS_MAX && semtab[i].sem != sem; i++); if (!--semtab[i].refcnt) { semtab[i].sem = 0; semtab[i].ino = 0; } pthread_spin_unlock(&lock); return munmap(sem, sizeof *sem); } |