+/*
+ * Copyright (C) 2006-2008 Andre Noll <maan@systemlinux.org>
+ *
+ * Licensed under the GPL v2. For licencing details see COPYING.
+ */
+
+/** \file ipc.c interprocess communication and shared memory helpers */
+
#include "para.h"
#include "error.h"
#include "ipc.h"
#include <sys/ipc.h>
#include <sys/shm.h>
+#include <sys/sem.h>
-
+/**
+ * define a new mutex
+ *
+ * \return the identifier for the new mutex on success, \a -E_SEM_GET
+ * on errors.
+ *
+ * \sa semget(2)
+ */
int mutex_new(void)
{
int ret = semget(IPC_PRIVATE, 1, IPC_CREAT | 0666);
return ret < 0? -E_SEM_GET : ret;
}
-int mutex_remove(int id)
+/**
+ * destroy a mutex
+ *
+ * \param id the identifier of the mutex to be destroyed
+ *
+ * \return Positive on success, \a -E_SEM_REMOVE on errors.
+ *
+ * \sa semctl(2)
+ */
+int mutex_destroy(int id)
{
int ret = semctl(id, 0, IPC_RMID);
return ret < 0? -E_SEM_REMOVE : 1;
static void para_semop(int id, struct sembuf *sops, int num)
{
- if (semop(id, sops, num) >= 0)
+ do {
+ if (semop(id, sops, num) >= 0)
+ return;
+ } while (errno == EINTR);
+ if (errno == EIDRM) {
+ PARA_NOTICE_LOG("semaphore set %d was removed\n", id);
return;
- PARA_WARNING_LOG("semop failed (%s), retrying\n", strerror(errno));
- while (semop(id, sops, num) < 0)
- ; /* nothing */
+ }
+ PARA_EMERG_LOG("fatal semop error %s: pid %d\n", strerror(errno),
+ (int)getpid());
+ exit(EXIT_FAILURE);
}
/**
* lock the given mutex
*
+ * \param id of the shared memory area to lock
+ *
+ * This function either succeeds or aborts.
+ *
* \sa semop(2), struct misc_meta_data
*/
void mutex_lock(int id)
/**
* unlock a mutex
*
+ * \param id the identifier of the mutex
+ *
+ * This function either succeeds or aborts.
+ *
* \sa semop(2), struct misc_meta_data
*/
void mutex_unlock(int id)
/**
* create a new shared memory area of given size
- *
+ *
+ * \param size the size of the shared memory area to create
+ *
+ * \return The id of the shared memory areay on success, \a -E_SHM_GET on errors.
+ *
* \sa shmget(2)
*/
int shm_new(size_t size)
/**
* destroy the given shared memory area
+ *
+ * \param id the shared memory id
+ *
+ * \return The return value of the underlying shmctl() call on success,
+ * \a -E_SHM_DESTROY on errors.
+ *
* \sa shmctl(2)
- **/
+ */
int shm_destroy(int id)
{
struct shmid_ds shm_desc;
}
/**
- * attach a shared memory area
+ * attach a shared memory segment
*
- * \sa semop(2)
+ * \param id the identifier of the shared memory segment to attach
+ * \param mode either ATTACH_RO (read only) or ATTACH_RW (read/write)
+ * \param result points to the attached area just attached
+ *
+ * \return positive on success, \a -E_SHM_ATTACH on errors.
+ *
+ * \sa shmat(2)
*/
-void *shm_attach(int id, enum shm_attach_mode mode)
+int shm_attach(int id, enum shm_attach_mode mode, void **result)
{
- if (mode == ATTACH_RW)
- return shmat(id, NULL, 0);
- return shmat(id, NULL, SHM_RDONLY);
+ if (mode == ATTACH_RW) {
+ *result = shmat(id, NULL, 0);
+ return *result? 1 : -E_SHM_ATTACH;
+ }
+ *result = shmat(id, NULL, SHM_RDONLY);
+ return *result? 1 : -E_SHM_ATTACH;
}
+
+/**
+ * detach a shared memory segment
+ *
+ * \param addr the address of the attached segment
+ *
+ * \return positive on success, \a -E_SHM_DETACH on errors.
+ *
+ * \sa shmdt(2)
+ */
int shm_detach(void *addr)
{
int ret = shmdt(addr);