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[simgrid.git] / src / msg / msg_task.c

diff --git a/src/msg/msg_task.c b/src/msg/msg_task.c
index 522e553..bdbbc47 100644 (file)
--- a/src/msg/msg_task.c
+++ b/src/msg/msg_task.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2004-2013. The SimGrid Team.
+/* Copyright (c) 2004-2014. The SimGrid Team.
  * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
@@ -475,7 +475,23 @@ void MSG_task_set_bound(msg_task_t task, double bound)
  *
  * \param task a target task
  * \param host the host having a multi-core CPU
- * \param mask the value specifying the CPU affinity setting of the task
+ * \param mask the bit mask of a new CPU affinity setting for the task
+ *
+ *
+ * Usage:
+ * 0. Define a host with multiple cores.
+ *    \<host id="PM0" power="1E8" core="2"/\>
+ *
+ * 1. Pin a given task to the first CPU core of a host.
+ *   MSG_task_set_affinity(task, pm0, 0x01);
+ *
+ * 2. Pin a given task to the third CPU core of a host. Turn on the third bit of the mask.
+ *   MSG_task_set_affinity(task, pm0, 0x04); // 0x04 == 100B
+ *
+ * 3. Pin a given VM to the first CPU core of a host.
+ *   MSG_vm_set_affinity(vm, pm0, 0x01);
+ *
+ * See examples/msg/cloud/multicore.c for more information.
  *
  *
  * Note:
@@ -496,7 +512,12 @@ void MSG_task_set_affinity(msg_task_t task, msg_host_t host, unsigned long mask)
 
   if (mask == 0) {
     /* 0 means clear */
-    xbt_dict_remove_ext(task->simdata->affinity_mask_db, (char *) host, sizeof(host));
+    {
+      /* We need remove_ext() not throwing exception. */
+      void *ret = xbt_dict_get_or_null_ext(task->simdata->affinity_mask_db, (char *) host, sizeof(msg_host_t));
+      if (ret != NULL)
+        xbt_dict_remove_ext(task->simdata->affinity_mask_db, (char *) host, sizeof(host));
+    }
   } else
     xbt_dict_set_ext(task->simdata->affinity_mask_db, (char *) host, sizeof(host), (void *) mask, NULL);