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 #define MAX_SEMOP_RETRIES 500
   8
   9 int mutex_new(void)
  10 {
  11         int ret = semget(IPC_PRIVATE, 1, IPC_CREAT | 0666);
  12         return ret < 0?  -E_SEM_GET : ret;
  13 }
  14
  15 int mutex_destroy(int id)
  16 {
  17         int ret = semctl(id, 0, IPC_RMID);
  18         return ret < 0? -E_SEM_REMOVE : 1;
  19 }
  20
  21 static void para_semop(int id, struct sembuf *sops, int num)
  22 {
  23         int i;
  24
  25         for (i = 0; i < MAX_SEMOP_RETRIES; i++)
  26                 if (semop(id, sops, num) >= 0)
  27                         return;
  28         PARA_EMERG_LOG("semop failed %d times, aborting\n", MAX_SEMOP_RETRIES);
  29         exit(EXIT_FAILURE);
  30 }
  31
  32 /**
  33  * lock the given mutex
  34  *
  35  * \sa semop(2), struct misc_meta_data
  36  */
  37 void mutex_lock(int id)
  38 {
  39         struct sembuf sops[2] = {
  40                 {
  41                         .sem_num = 0,
  42                         .sem_op = 0,
  43                         .sem_flg = SEM_UNDO
  44                 },
  45                 {
  46                         .sem_num = 0,
  47                         .sem_op = 1,
  48                         .sem_flg = SEM_UNDO
  49                 }
  50         };
  51         para_semop(id, sops, 2);
  52 }
  53
  54 /**
  55  * unlock a mutex
  56  *
  57  * \sa semop(2), struct misc_meta_data
  58  */
  59 void mutex_unlock(int id)
  60 {
  61         struct sembuf sops[1] = {
  62                 {
  63                         .sem_num = 0,
  64                         .sem_op = -1,
  65                         .sem_flg = SEM_UNDO
  66                 },
  67         };
  68         para_semop(id, sops, 1);
  69 }
  70
  71 /**
  72  * create a new shared memory area of given size
  73  *
  74  * \sa shmget(2)
  75  */
  76 int shm_new(size_t size)
  77 {
  78         int ret = shmget(IPC_PRIVATE, size, IPC_CREAT | IPC_EXCL | 0600);
  79         return ret < 0 ? -E_SHM_GET : ret;
  80 }
  81
  82 /**
  83  * destroy the given shared memory area
  84  * \sa shmctl(2)
  85  **/
  86 int shm_destroy(int id)
  87 {
  88         struct shmid_ds shm_desc;
  89         int ret = shmctl(id, IPC_RMID, &shm_desc);
  90         return ret < 0? -E_SHM_DESTROY : ret;
  91 }
  92
  93 /**
  94  * attach a shared memory area
  95  *
  96  * \sa semop(2)
  97  */
  98 int shm_attach(int id, enum shm_attach_mode mode, void **result)
  99 {
 100         if (mode == ATTACH_RW) {
 101                 *result = shmat(id, NULL, 0);
 102                 return *result? 1 : -E_SHM_ATTACH;
 103         }
 104         *result = shmat(id, NULL, SHM_RDONLY);
 105         return *result? 1 : -E_SHM_ATTACH;
 106 }
 107
 108 int shm_detach(void *addr)
 109 {
 110         int ret = shmdt(addr);
 111         return ret < 0? -E_SHM_DETACH : 1;
 112 }