This initial vfork() check-in was a little pollyanna-ish

git-svn-id: http://svn.code.sf.net/p/nuttx/code/trunk@5487 42af7a65-404d-4744-a932-0658087f49c3

4 files changed, 271 insertions, 2 deletions

diff --git a/nuttx/sched/Makefile b/nuttx/sched/Makefile
index 82f74fc3c..23d1e9938 100644
--- a/nuttx/sched/Makefile
+++ b/nuttx/sched/Makefile
@@ -45,7 +45,7 @@ MISC_SRCS	= os_start.c os_bringup.c errno_getptr.c errno_get.c errno_set.c \
 
 TSK_SRCS	= prctl.c task_create.c task_init.c task_setup.c task_activate.c \
 		  task_start.c task_delete.c task_deletecurrent.c task_exithook.c \
-		  task_restart.c exit.c getpid.c sched_addreadytorun.c \
+		  task_restart.c task_vfork.c exit.c getpid.c sched_addreadytorun.c \
 		  sched_removereadytorun.c sched_addprioritized.c sched_mergepending.c \
 		  sched_addblocked.c sched_removeblocked.c sched_free.c sched_gettcb.c \
 		  sched_verifytcb.c sched_releasetcb.c
diff --git a/nuttx/sched/sched_setuptaskfiles.c b/nuttx/sched/sched_setuptaskfiles.c
index fe0b14143..d01b8d4cd 100644
--- a/nuttx/sched/sched_setuptaskfiles.c
+++ b/nuttx/sched/sched_setuptaskfiles.c
@@ -200,7 +200,8 @@ static inline void sched_dupsockets(FAR _TCB *tcb)
  *   tcb - tcb of the new task.
  *
  * Return Value:
- *   None
+ *   Zero (OK) is returned on success; A negated errno value is returned on
+ *   failure.
  *
  * Assumptions:
  *
diff --git a/nuttx/sched/task_create.c b/nuttx/sched/task_create.c
index 4d92c9bb0..801706cbf 100644
--- a/nuttx/sched/task_create.c
+++ b/nuttx/sched/task_create.c
@@ -169,6 +169,8 @@ static int thread_create(const char *name, uint8_t type, int priority,
   ret = task_activate(tcb);
   if (ret != OK)
     {
+      /* The TCB was added to the active task list by task_schedsetup() */
+
       dq_rem((FAR dq_entry_t*)tcb, (dq_queue_t*)&g_inactivetasks);
       goto errout_with_tcb;
     }
diff --git a/nuttx/sched/task_vfork.c b/nuttx/sched/task_vfork.c
new file mode 100644
index 000000000..93fcb46da
--- /dev/null
+++ b/nuttx/sched/task_vfork.c
@@ -0,0 +1,266 @@
+/****************************************************************************
+ * sched/task_vfork
+ *
+ *   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <stdint.h>
+#include <assert.h>
+#include <queue.h>
+#include <errno.h>
+
+#include <nuttx/sched.h>
+
+#include "os_internal.h"
+#include "env_internal.h"
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: task_vforksetup
+ *
+ * Description:
+ *   The vfork() function has the same effect as fork(), except that the
+ *   behavior is undefined if the process created by vfork() either modifies
+ *   any data other than a variable of type pid_t used to store the return
+ *   value from vfork(), or returns from the function in which vfork() was
+ *   called, or calls any other function before successfully calling _exit()
+ *   or one of the exec family of functions. 
+ *
+ *   This functin provides one step in the overall vfork() sequence:  It
+ *   Allocates and initializes the child task's TCB.  The overall sequence is:
+ *
+ *   1) User code calls vfork().  vfork() is provided in architecture-specific
+ *      code.
+ *   2) vfork()and calls task_vforksetup().
+ *   3) task_vforksetup() allocates and configures the child task's TCB.  This
+ *      consists of:
+ *      - Allocation of the child task's TCB.
+ *      - Initialization of file descriptors and streams
+ *      - Configuration of environment variables
+ *      - Setup the intput parameters for the task.
+ *      - Initialization of the TCB (including call to up_initial_state()
+ *   4) up_vfork() provides any additional operating context. up_vfork must:
+ *      - Allocate and initialize the stack
+ *      - Initialize special values in any CPU registers that were not
+ *        already configured by up_initial_state()
+ *   5) up_vfork() then calls task_vforkstart()
+ *   6) task_vforkstart() then executes the child thread.
+ *
+ * Input Paremeters:
+ *   retaddr - The return address from vfork() where the child task
+ *     will be started.
+ *
+ * Returned Value:
+ *   Upon successful completion, task_vforksetup() returns a pointer to
+ *   newly allocated and initalized child task's TCB.  NULL is returned
+ *   on any failure and the errno is set appropriately.
+ *
+ ****************************************************************************/
+
+FAR _TCB *task_vforksetup(start_t retaddr)
+{
+  _TCB *parent = (FAR _TCB *)g_readytorun.head;
+  _TCB *child;
+  int priority;
+  int ret;
+
+  DEBUGASSERT(retaddr);
+
+  /* Allocate a TCB for the child task. */
+
+  child = (FAR _TCB*)kzalloc(sizeof(_TCB));
+  if (!child)
+    {
+      set_errno(ENOMEM);
+      return NULL;
+    }
+
+  /* Associate file descriptors with the new task */
+
+#if CONFIG_NFILE_DESCRIPTORS > 0 || CONFIG_NSOCKET_DESCRIPTORS > 0
+  ret = sched_setuptaskfiles(child);
+  if (ret != OK)
+    {
+      goto errout_with_tcb;
+    }
+#endif
+
+  /* Clone the parent's task environment */
+
+  (void)env_dup(child);
+
+  /* Mark the type of this thread (this setting will be needed in
+   * task_schedsetup() when up_initial_state() is called.
+   */
+
+  child->flags |= TCB_FLAG_TTYPE_TASK;
+
+  /* Get the priority of the parent task */
+
+#ifdef CONFIG_PRIORITY_INHERITANCE
+  priority = parent->base_priority;  /* "Normal," unboosted priority */
+#else
+  priority = parent->sched_priority;  /* Current priority */
+#endif
+
+  /* Initialize the task control block.  This calls up_initial_state() */
+
+  ret = task_schedsetup(child, priority, retaddr, parent->entry.main);
+  if (ret != OK)
+    {
+      goto errout_with_tcb;
+    }
+
+  return child;
+
+errout_with_tcb:
+  sched_releasetcb(child);
+  set_errno(-ret);
+  return NULL;
+}
+
+/****************************************************************************
+ * Name: task_vforkstart
+ *
+ * Description:
+ *   The vfork() function has the same effect as fork(), except that the
+ *   behavior is undefined if the process created by vfork() either modifies
+ *   any data other than a variable of type pid_t used to store the return
+ *   value from vfork(), or returns from the function in which vfork() was
+ *   called, or calls any other function before successfully calling _exit()
+ *   or one of the exec family of functions. 
+ *
+ *   This functin provides one step in the overall vfork() sequence:  It
+ *   starts execution of the previously initialized TCB.  The overall
+ *   sequence is:
+ *
+ *   1) User code calls vfork()
+ *   2) Architecture-specific code provides vfork()and calls task_vforksetup().
+ *   3) task_vforksetup() allocates and configures the child task's TCB.  This
+ *      consists of:
+ *      - Allocation of the child task's TCB.
+ *      - Initialization of file descriptors and streams
+ *      - Configuration of environment variables
+ *      - Setup the intput parameters for the task.
+ *      - Initialization of the TCB (including call to up_initial_state()
+ *   4) vfork() provides any additional operating context. vfork must:
+ *      - Allocate and initialize the stack
+ *      - Initialize special values in any CPU registers that were not
+ *        already configured by up_initial_state()
+ *   5) vfork() then calls task_vforkstart()
+ *   6) task_vforkstart() then executes the child thread.
+ *
+ * Input Paremeters:
+ *   retaddr - The return address from vfork() where the child task
+ *     will be started.
+ *
+ * Returned Value:
+ *   Upon successful completion, vfork() returns 0 to the child process and
+ *   returns the process ID of the child process to the parent process.
+ *   Otherwise, -1 is returned to the parent, no child process is created,
+ *   and errno is set to indicate the error. 
+ *
+ ****************************************************************************/
+
+pid_t task_vforkstart(FAR _TCB *child)
+{
+  FAR const char *name;
+  pid_t pid;
+  int ret;
+
+  DEBUGASSERT(child);
+
+  /* Setup to pass parameters to the new task */
+
+#if CONFIG_TASK_NAME_SIZE > 0
+  name = parent->name;
+#else
+  name = "<noname>";
+#endif
+
+  (void)task_argsetup(child, name, (const char **)NULL);
+
+  /* Get the assigned pid before we start the task */
+
+  pid = (int)child->pid;
+
+  /* Activate the task */
+
+  ret = task_activate(child);
+  if (ret != OK)
+    {
+      task_vforkabort(child, -ret);
+      return ERROR;
+    }
+
+  return pid;
+}
+
+/****************************************************************************
+ * Name: task_vforkabort
+ *
+ * Description:
+ *   Recover from any errors after task_vforksetup() was called.
+ *
+ * Returned Value:
+ *   None
+ *
+ ****************************************************************************/
+
+void task_vforkabort(FAR _TCB *child, int errcode)
+{
+  /* The TCB was added to the active task list by task_schedsetup() */
+
+  dq_rem((FAR dq_entry_t*)child, (dq_queue_t*)&g_inactivetasks);
+
+  /* Release the TCB */
+
+  sched_releasetcb(child);
+  set_errno(errcode);
+}
\ No newline at end of file