ipc.c

   1 #include "para.h"
   2 #include "error.h"
   3 #include "ipc.h"
   4 #include <sys/ipc.h>
   5 #include <sys/shm.h>
   6
   7
   8 int mutex_new(void)
   9 {
  10         int ret = semget(IPC_PRIVATE, 1, IPC_CREAT | 0666);
  11         return ret < 0?  -E_SEM_GET : ret;
  12 }
  13
  14 int mutex_remove(int id)
  15 {
  16         int ret = semctl(id, 0, IPC_RMID);
  17         return ret < 0? -E_SEM_REMOVE : 1;
  18 }
  19
  20 static void para_semop(int id, struct sembuf *sops, int num)
  21 {
  22         if (semop(id, sops, num) >= 0)
  23                 return;
  24         PARA_WARNING_LOG("semop failed (%s), retrying\n", strerror(errno));
  25         while (semop(id, sops, num) < 0)
  26                 ; /* nothing */
  27 }
  28
  29 /**
  30  * lock the given mutex
  31  *
  32  * \sa semop(2), struct misc_meta_data
  33  */
  34 void mutex_lock(int id)
  35 {
  36         struct sembuf sops[2] = {
  37                 {
  38                         .sem_num = 0,
  39                         .sem_op = 0,
  40                         .sem_flg = SEM_UNDO
  41                 },
  42                 {
  43                         .sem_num = 0,
  44                         .sem_op = 1,
  45                         .sem_flg = SEM_UNDO
  46                 }
  47         };
  48         para_semop(id, sops, 2);
  49 }
  50
  51 /**
  52  * unlock a mutex
  53  *
  54  * \sa semop(2), struct misc_meta_data
  55  */
  56 void mutex_unlock(int id)
  57 {
  58         struct sembuf sops[1] = {
  59                 {
  60                         .sem_num = 0,
  61                         .sem_op = -1,
  62                         .sem_flg = SEM_UNDO
  63                 },
  64         };
  65         para_semop(id, sops, 1);
  66 }
  67
  68 /**
  69  * create a new shared memory area of given size
  70  *
  71  * \sa shmget(2)
  72  */
  73 int shm_new(size_t size)
  74 {
  75         int ret = shmget(IPC_PRIVATE, size, IPC_CREAT | IPC_EXCL | 0600);
  76         return ret < 0 ? -E_SHM_GET : ret;
  77 }
  78
  79 /**
  80  * destroy the given shared memory area
  81  * \sa shmctl(2)
  82  **/
  83 int shm_destroy(int id)
  84 {
  85         struct shmid_ds shm_desc;
  86         int ret = shmctl(id, IPC_RMID, &shm_desc);
  87         return ret < 0? -E_SHM_DESTROY : ret;
  88 }
  89
  90 /**
  91  * attach a shared memory area
  92  *
  93  * \sa semop(2)
  94  */
  95 void *shm_attach(int id, enum shm_attach_mode mode)
  96 {
  97         if (mode == ATTACH_RW)
  98                 return shmat(id, NULL, 0);
  99         return shmat(id, NULL, SHM_RDONLY);
 100 }
 101 int shm_detach(void *addr)
 102 {
 103         int ret = shmdt(addr);
 104         return ret < 0? -E_SHM_DETACH : 1;
 105 }