X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=ipc.c;h=b6c525ab07311a14dbfaefe637781e163c24dba5;hp=9ae2b3a09d1e1d98617e4502c16f7af2f0f54742;hb=0a2aa419ef9fcdb667ebcbe1a425802578aa153d;hpb=bad57eee70cdca87e8ba1af08d4e2ef6d2878620

diff --git a/ipc.c b/ipc.c
index 9ae2b3a0..b6c525ab 100644
--- a/ipc.c
+++ b/ipc.c
@@ -1,17 +1,57 @@
+/*
+ * Copyright (C) 2006-2007 Andre Noll <maan@systemlinux.org>
+ *
+ *     This program is free software; you can redistribute it and/or modify
+ *     it under the terms of the GNU General Public License as published by
+ *     the Free Software Foundation; either version 2 of the License, or
+ *     (at your option) any later version.
+ *
+ *     This program is distributed in the hope that it will be useful,
+ *     but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *     GNU General Public License for more details.
+ *
+ *     You should have received a copy of the GNU General Public License
+ *     along with this program; if not, write to the Free Software
+ *     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA.
+ */
+
+/** \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>
 
+/** abort if semget() failed that many times */
+#define MAX_SEMOP_RETRIES 500
 
+/**
+ * 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;
@@ -19,16 +59,22 @@ int mutex_remove(int id)
 
 static void para_semop(int id, struct sembuf *sops, int num)
 {
-	if (semop(id, sops, num) >= 0)
-		return;
-	PARA_WARNING_LOG("semop failed (%s), retrying\n", strerror(errno));
-	while (semop(id, sops, num) < 0)
-		; /* nothing */
+	int i;
+
+	for (i = 0; i < MAX_SEMOP_RETRIES; i++)
+		if (semop(id, sops, num) >= 0)
+			return;
+	PARA_EMERG_LOG("semop failed %d times, aborting\n", MAX_SEMOP_RETRIES);
+	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)
@@ -51,6 +97,10 @@ 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)
@@ -67,7 +117,11 @@ 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)
@@ -78,8 +132,14 @@ 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;
@@ -88,16 +148,35 @@ int shm_destroy(int id)
 }
 
 /**
- * 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);