From 80904539e63681b2dca74e3978effb17f0c071b0 Mon Sep 17 00:00:00 2001
From: patacongo <patacongo@42af7a65-404d-4744-a932-0658087f49c3>
Date: Fri, 25 Jan 2013 19:15:05 +0000
Subject: Add logic to keep track of members of a task group

git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5563 42af7a65-404d-4744-a932-0658087f49c3
---
 nuttx/sched/group_join.c | 103 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 92 insertions(+), 11 deletions(-)

(limited to 'nuttx/sched/group_join.c')

diff --git a/nuttx/sched/group_join.c b/nuttx/sched/group_join.c
index 987c1ba87..9dcea6599 100644
--- a/nuttx/sched/group_join.c
+++ b/nuttx/sched/group_join.c
@@ -41,8 +41,11 @@
 
 #include <sched.h>
 #include <assert.h>
+#include <errno.h>
 #include <debug.h>
 
+#include <nuttx/kmalloc.h>
+
 #include "os_internal.h"
 
 #ifdef HAVE_TASK_GROUP
@@ -50,6 +53,9 @@
 /*****************************************************************************
  * Pre-processor Definitions
  *****************************************************************************/
+/* Is this worth making a configuration option? */
+
+#define GROUP_REALLOC_MEMBERS 4
 
 /*****************************************************************************
  * Private Types
@@ -68,19 +74,21 @@
  *****************************************************************************/
 
 /*****************************************************************************
- * Name: group_join
+ * Name: group_bind
  *
  * Description:
- *   Copy the group structure reference from one TCB to another, incrementing
- *   the refrence count on the group.  This function is called when a pthread
- *   is produced within the task group so that the pthread can share the
- *   resources of the task group.
+ *   A thread joins the group when it is created.  This is a two step process,
+ *   first, the group must bound to the new threads TCB.  group_bind() does
+ *   this (at the return from group_join, things are a little unstable:  The
+ *   group has been bound, but tg_nmembers hs not yet been incremented).
+ *   Then, after the new thread is initialized and has a PID assigned to it,
+ *   group_join() is called, incrementing the tg_nmembers count on the group.  
  *
  * Parameters:
  *   tcb - The TCB of the new "child" task that need to join the group.
  *
  * Return Value:
- *   None
+ *   0 (OK) on success; a negated errno value on failure.
  *
  * Assumptions:
  * - The parent task from which the group will be inherited is the task at
@@ -90,18 +98,91 @@
  *
  *****************************************************************************/
 
-void group_join(FAR _TCB *tcb)
+int group_bind(FAR _TCB *tcb)
 {
   FAR _TCB *ptcb = (FAR _TCB *)g_readytorun.head;
 
   DEBUGASSERT(ptcb && tcb && ptcb->group && !tcb->group);
 
-  /* Copy the group reference from the parent to the child, incrementing the
-   * reference count.
-   */
+  /* Copy the group reference from the parent to the child */
 
   tcb->group = ptcb->group;
-  ptcb->group->tg_crefs++;
+  return OK;
+}
+
+/*****************************************************************************
+ * Name: group_join
+ *
+ * Description:
+ *   A thread joins the group when it is created.  This is a two step process,
+ *   first, the group must bound to the new threads TCB.  group_bind() does
+ *   this (at the return from group_join, things are a little unstable:  The
+ *   group has been bound, but tg_nmembers hs not yet been incremented).
+ *   Then, after the new thread is initialized and has a PID assigned to it,
+ *   group_join() is called, incrementing the tg_nmembers count on the group.  
+ *
+ * Parameters:
+ *   tcb - The TCB of the new "child" task that need to join the group.
+ *
+ * Return Value:
+ *   0 (OK) on success; a negated errno value on failure.
+ *
+ * Assumptions:
+ * - The parent task from which the group will be inherited is the task at
+ *   the thead of the ready to run list.
+ * - Called during thread creation in a safe context.  No special precautions
+ *   are required here.
+ *
+ *****************************************************************************/
+
+int group_join(FAR _TCB *tcb)
+{
+#ifdef HAVE_GROUP_MEMBERS
+  FAR struct task_group_s *group;
+
+  DEBUGASSERT(tcb && tcb->group &&
+              tcb->group->tg_nmembers < UINT8_MAX);
+
+  /* Get the group from the TCB */
+
+  group = tcb->group;
+  
+  /* Will we need to extend the size of the array of groups? */
+
+  if (group->tg_nmembers >= group->tg_mxmembers)
+    {
+      FAR pid_t *newmembers;
+      unsigned int newmax;
+
+      /* Yes... reallocate the array of members */
+
+      newmax = group->tg_mxmembers + GROUP_REALLOC_MEMBERS;
+      if (newmax > UINT8_MAX)
+        {
+          newmax = UINT8_MAX;
+        }
+
+      newmembers = (FAR pid_t *)
+        krealloc(group->tg_members, sizeof(pid_t) * newmax);
+
+      if (!newmembers)
+        {
+          return -ENOMEM;
+        }
+
+      /* Save the new number of members in the reallocated members array */
+
+      group->tg_members   = newmembers;
+      group->tg_mxmembers = newmax;
+    }
+
+  /* Assign this new pid to the group. */
+
+  group->tg_members[group->tg_nmembers] = tcb->pid;
+#endif
+
+  group->tg_nmembers++;
+  return OK;
 }
 
 #endif /* HAVE_TASK_GROUP */
-- 
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