X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=ipc.c;h=49d2d96515dbf49bc5a9f7ace0786d5f68acc936;hp=ae9ad574bbd5840be8cee0c034c8f9e0e48cc7cc;hb=08bd4a0d28f709a3b0ca5598e2a3eb62d4378800;hpb=c5517c98d28a74a89086b0641e3633d16eaf9df7

diff --git a/ipc.c b/ipc.c
index ae9ad574..49d2d965 100644
--- a/ipc.c
+++ b/ipc.c
@@ -1,16 +1,56 @@
+/*
+ * Copyright (C) 2006 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, -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;
 }
 
+/**
+ * destroy a mutex
+ *
+ * \param id the identifier of the mutex to be destroyed
+ *
+ * \returns Positive on success, -E_SEM_REMOVE on errors.
+ *
+ * \sa semctl(2)
+ */
 int mutex_destroy(int id)
 {
 	int ret = semctl(id, 0, IPC_RMID);
@@ -19,16 +59,20 @@ int mutex_destroy(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
  *
+ * This function either succeeds or aborts.
+ *
  * \sa semop(2), struct misc_meta_data
  */
 void mutex_lock(int id)
@@ -51,6 +95,10 @@ 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)
@@ -88,9 +136,15 @@ int shm_destroy(int id)
 }
 
 /**
- * attach a shared memory area
+ * attach a shared memory segment
+ *
+ * \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 arer which to the
  *
- * \sa semop(2)
+ * \returns positive on success, -E_SHM_ATTACH on errrors.
+ *
+ * \sa shmat(2)
  */
 int shm_attach(int id, enum shm_attach_mode mode, void **result)
 {
@@ -102,6 +156,15 @@ int shm_attach(int id, enum shm_attach_mode mode, void **result)
 	return *result? 1 : -E_SHM_ATTACH;
 }
 
+/**
+ * detach a shared memory segment
+ *
+ * \param addr the address of the attached segment
+ *
+ * \returns positive on success, -E_SHM_DETACH on errors.
+ *
+ * \sa shmdt(2)
+ */
 int shm_detach(void *addr)
 {
 	int ret = shmdt(addr);