Use pthreads instead of tasks in BG

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@855 42af7a65-404d-4744-a932-0658087f49c3

4 files changed, 355 insertions, 174 deletions

diff --git a/nuttx/examples/nsh/nsh.h b/nuttx/examples/nsh/nsh.h
index 69ed0f030..76e2701ba 100644
--- a/nuttx/examples/nsh/nsh.h
+++ b/nuttx/examples/nsh/nsh.h
@@ -49,6 +49,14 @@
  * Definitions
  ****************************************************************************/
 
+/* The telnetd interface requires pthread support */
+
+#ifdef CONFIG_DISABLE_PTHREAD
+#  undef CONFIG_EXAMPLES_NSH_TELNET
+#endif
+
+/* One front end must be defined */
+
 #if !defined(CONFIG_EXAMPLES_NSH_CONSOLE) && !defined(CONFIG_EXAMPLES_NSH_TELNET)
 #  error "No NSH front end defined"
 #endif
@@ -97,7 +105,7 @@
 
 /* Define to enable dumping of all input/output buffers */
 
-#undef CONFIG_EXAMPLES_NSH_TELNETD_DUMPBUFFER
+#define CONFIG_EXAMPLES_NSH_TELNETD_DUMPBUFFER 1
 #undef CONFIG_EXAMPLES_NSH_FULLPATH
 
 /* Make sure that the home directory is defined */
@@ -107,7 +115,6 @@
 #endif
 
 #define nsh_clone(v)           (v)->clone(v)
-#define nsh_addref(v)          (v)->addref(v)
 #define nsh_release(v)         (v)->release(v)
 #define nsh_linebuffer(v)      (v)->linebuffer(v)
 #define nsh_redirect(v,f,s)    (v)->redirect(v,f,s)
@@ -151,11 +158,15 @@ struct nsh_state_s
 
 struct nsh_parser_s
 {
+#ifndef CONFIG_DISABLE_PTHREAD
   boolean   np_bg;       /* TRUE: The last command executed in background */
+#endif
   boolean   np_redirect; /* TRUE: Output from the last command was re-directed */
   boolean   np_fail;     /* TRUE: The last command failed */
   ubyte     np_ndx;      /* Current index into np_st[] */
+#ifndef CONFIG_DISABLE_PTHREAD
   int       np_nice;     /* "nice" value applied to last background cmd */
+#endif
 
   /* This is a stack of parser state information.  It supports nested
    * execution of commands that span multiple lines (like if-then-else-fi)
@@ -171,10 +182,12 @@ struct nsh_vtbl_s
    * -- all of which must be done in a way that is unique to the nature
    * of the front end.
    */
-   
+
+#ifndef CONFIG_DISABLE_PTHREAD
   FAR struct nsh_vtbl_s *(*clone)(FAR struct nsh_vtbl_s *vtbl);
   void (*addref)(FAR struct nsh_vtbl_s *vtbl);
   void (*release)(FAR struct nsh_vtbl_s *vtbl);
+#endif
   int (*output)(FAR struct nsh_vtbl_s *vtbl, const char *fmt, ...);
   FAR char *(*linebuffer)(FAR struct nsh_vtbl_s *vtbl);
   void (*redirect)(FAR struct nsh_vtbl_s *vtbl, int fd, FAR ubyte *save);
diff --git a/nuttx/examples/nsh/nsh_main.c b/nuttx/examples/nsh/nsh_main.c
index 35f88b72a..7ca2937bb 100644
--- a/nuttx/examples/nsh/nsh_main.c
+++ b/nuttx/examples/nsh/nsh_main.c
@@ -1,5 +1,5 @@
 /****************************************************************************
- * nsh_main.c
+ * examples/nsh/nsh_main.c
  *
  *   Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
@@ -48,6 +48,11 @@
 #include <sched.h>
 #include <fcntl.h>
 #include <errno.h>
+#include <debug.h>
+
+#ifndef CONFIG_DISABLE_PTHREAD
+#  include <pthread.h>
+#endif
 
 #include "nsh.h"
 
@@ -55,6 +60,30 @@
  * Definitions
  ****************************************************************************/
 
+/* Argument list size
+ *
+ *   argv[0]:      The command name. 
+ *   argv[1]:      The beginning of argument (up to NSH_MAX_ARGUMENTS)
+ *   argv[argc-3]: Possibly '>' or '>>'
+ *   argv[argc-2]: Possibly <file>
+ *   argv[argc-1]: Possibly '&' (if pthreads are enabled)
+ *   argv[argc]:   NULL terminating pointer
+ *
+ * Maximum size is NSH_MAX_ARGUMENTS+5
+ */
+
+#ifndef CONFIG_DISABLE_PTHREAD
+#  define MAX_ARGV_ENTRIES (NSH_MAX_ARGUMENTS+5)
+#else
+#  define MAX_ARGV_ENTRIES (NSH_MAX_ARGUMENTS+4)
+#endif
+
+#if CONFIG_RR_INTERVAL > 0
+# define SCHED_NSH SCHED_RR
+#else
+# define SCHED_NSH SCHED_FIFO
+#endif
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
@@ -68,6 +97,16 @@ struct cmdmap_s
   const char *usage;      /* Usage instructions for 'help' command */
 };
 
+#ifndef CONFIG_DISABLE_PTHREAD
+struct cmdarg_s
+{
+  FAR struct nsh_vtbl_s *vtbl;      /* For front-end interaction */
+  int fd;                           /* FD for output redirection */
+  int argc;                         /* Number of arguments in argv */
+  FAR char *argv[MAX_ARGV_ENTRIES]; /* Argument list */
+};
+#endif
+
 /****************************************************************************
  * Private Function Prototypes
  ****************************************************************************/
@@ -193,7 +232,11 @@ static int cmd_help(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
   const struct cmdmap_s *ptr;
 
   nsh_output(vtbl, "NSH command forms:\n");
-  nsh_output(vtbl, "  [nice [-d <niceness>>]] <cmd> [[> <file>|>> <file>] &]\n");
+#ifndef CONFIG_DISABLE_PTHREAD
+  nsh_output(vtbl, "  [nice [-d <niceness>>]] <cmd> [> <file>|>> <file>] [&]\n");
+#else
+  nsh_output(vtbl, "  <cmd> [> <file>|>> <file>]\n");
+#endif
   nsh_output(vtbl, "OR\n");
   nsh_output(vtbl, "  if <cmd>\n");
   nsh_output(vtbl, "  then\n");
@@ -240,32 +283,22 @@ static int cmd_exit(FAR struct nsh_vtbl_s *vtbl, int argc, char **argv)
  * Name: nsh_execute
  ****************************************************************************/
 
-static int nsh_execute(int argc, char *argv[])
+static int nsh_execute(FAR struct nsh_vtbl_s *vtbl, int argc, char *argv[])
 {
    const struct cmdmap_s *cmdmap;
    const char            *cmd;
-   struct nsh_vtbl_s     *vtbl;
    cmd_t                  handler = cmd_unrecognized;
    int                    ret;
 
-   /* Parse all of the arguments following the command name.  The form
-    * of argv is:
+   /* The form of argv is:
     *
-    * argv[0]:      Task name "nsh_execute"
-    * argv[1]:      This is string version of the vtbl needed to execute
-    *               the command (under telnetd).  It is a string because
-    *               binary values cannot be provided via char *argv[]
-    * argv[2]:      The command name.  This is argv[0] when the arguments
+    * argv[0]:      The command name.  This is argv[0] when the arguments
     *               are, finally, received by the command vtblr
-    * argv[3]:      The beginning of argument (up to NSH_MAX_ARGUMENTS)
+    * argv[1]:      The beginning of argument (up to NSH_MAX_ARGUMENTS)
     * argv[argc]:   NULL terminating pointer
-    *
-    * Maximum size is NSH_MAX_ARGUMENTS+4
     */
 
-   vtbl  = (struct nsh_vtbl_s*)strtol(argv[1], NULL, 16);
-   cmd     = argv[2];
-   argc   -= 2;
+   cmd = argv[0];
 
    /* See if the command is one that we understand */
 
@@ -304,12 +337,93 @@ static int nsh_execute(int argc, char *argv[])
          }
      }
 
-   ret = handler(vtbl, argc, &argv[2]);
-   nsh_release(vtbl);
+   ret = handler(vtbl, argc, argv);
    return ret;
 }
 
 /****************************************************************************
+ * Name: nsh_releaseargs
+ ****************************************************************************/
+
+#ifndef CONFIG_DISABLE_PTHREAD
+static void nsh_releaseargs(struct cmdarg_s *arg)
+{
+  FAR struct nsh_vtbl_s *vtbl = arg->vtbl;
+  int i;
+
+  /* If the output was redirected, then file descriptor should
+   * be closed.  The created task has its one, independent copy of
+   * the file descriptor
+   */
+
+  if (vtbl->np.np_redirect)
+    {
+      (void)close(arg->fd);
+    }
+
+  /* Released the cloned vtbl instance */
+
+  nsh_release(vtbl);
+
+  /* Release the cloned args */
+
+  for (i = 0; i < arg->argc; i++)
+    {
+      free(arg->argv[i]);
+    }
+  free(arg);
+}
+#endif
+
+/****************************************************************************
+ * Name: nsh_child
+ ****************************************************************************/
+
+#ifndef CONFIG_DISABLE_PTHREAD
+static pthread_addr_t nsh_child(pthread_addr_t arg)
+{
+  struct cmdarg_s *carg = (struct cmdarg_s *)arg;
+  int ret;
+
+  dbg("BG %s\n", carg->argv[0]);
+
+  /* Execute the specified command on the child thread */
+
+  ret = nsh_execute(carg->vtbl, carg->argc, carg->argv);
+
+  /* Released the cloned arguments */
+
+  dbg("BG %s complete\n", carg->argv[0]);
+  nsh_releaseargs(carg);
+  return (void*)ret;
+}
+#endif
+
+/****************************************************************************
+ * Name: nsh_cloneargs
+ ****************************************************************************/
+
+static inline struct cmdarg_s *nsh_cloneargs(FAR struct nsh_vtbl_s *vtbl,
+                                             int fd, int argc, char *argv[])
+{
+  struct cmdarg_s *ret = (struct cmdarg_s *)zalloc(sizeof(struct cmdarg_s));
+  int i;
+
+  if (ret)
+    {
+      ret->vtbl = vtbl;
+      ret->fd   = fd;
+      ret->argc = argc;
+
+      for (i = 0; i < argc; i++)
+        {
+          ret->argv[i] = strdup(argv[i]);
+        }
+    }
+  return ret;
+}
+
+/****************************************************************************
  * Name: nsh_argument
  ****************************************************************************/
 
@@ -518,7 +632,7 @@ static inline int nsh_ifthenelse(FAR struct nsh_vtbl_s *vtbl, FAR char **ppcmd,
           if (np->np_ndx >= CONFIG_EXAMPLES_NSH_NESTDEPTH-1)
             {
               nsh_output(vtbl, g_fmtdeepnesting, "if");
-              goto errout;            
+              goto errout;
             }
 
           /* "Push" the old state and set the new state */
@@ -592,7 +706,7 @@ static inline int nsh_ifthenelse(FAR struct nsh_vtbl_s *vtbl, FAR char **ppcmd,
           if (np->np_ndx < 1) /* Shouldn't happen */
             {
               nsh_output(vtbl, g_fmtinternalerror, "if");
-              goto errout;            
+              goto errout;
             }
 
           /* "Pop" the previous state */
@@ -640,10 +754,11 @@ static inline int nsh_saveresult(FAR struct nsh_vtbl_s *vtbl, boolean result)
  * Name: nsh_nice
  ****************************************************************************/
 
+#ifndef CONFIG_DISABLE_PTHREAD
 static inline int nsh_nice(FAR struct nsh_vtbl_s *vtbl, FAR char **ppcmd, FAR char **saveptr)
 {
   FAR char *cmd = *ppcmd;
- 
+
   vtbl->np.np_nice = 0;
   if (cmd)
     {
@@ -684,6 +799,7 @@ static inline int nsh_nice(FAR struct nsh_vtbl_s *vtbl, FAR char **ppcmd, FAR ch
     }
   return OK;
 }
+#endif
 
 /****************************************************************************
  * Public Functions
@@ -711,12 +827,12 @@ int user_start(int argc, char *argv[])
    * can both raise and lower the priority.
    */
 
-  mid_priority = (sched_get_priority_max(SCHED_RR) + sched_get_priority_min(SCHED_RR)) >> 1;
+  mid_priority = (sched_get_priority_max(SCHED_NSH) + sched_get_priority_min(SCHED_NSH)) >> 1;
     {
       struct sched_param param;
 
       param.sched_priority = mid_priority;
-      (void)sched_setscheduler(0, SCHED_RR, &param);
+      (void)sched_setscheduler(0, SCHED_NSH, &param);
     }
 
   /* If both the console and telnet are selected as front-ends, then run
@@ -754,8 +870,7 @@ int user_start(int argc, char *argv[])
 
 int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
 {
-  FAR char *argv[NSH_MAX_ARGUMENTS+7];
-  FAR char  strvtbl[2*sizeof(FAR char*)+3];
+  FAR char *argv[MAX_ARGV_ENTRIES];
   FAR char *saveptr;
   FAR char *cmd;
   FAR char *redirfile = NULL;
@@ -766,7 +881,7 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
 
   /* Initialize parser state */
 
-  memset(argv, 0, (NSH_MAX_ARGUMENTS+4)*sizeof(char*));
+  memset(argv, 0, MAX_ARGV_ENTRIES*sizeof(FAR char *));
   vtbl->np.np_bg       = FALSE;
   vtbl->np.np_redirect = FALSE;
 
@@ -784,10 +899,12 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
 
   /* Handle nice */
 
+#ifndef CONFIG_DISABLE_PTHREAD
   if (nsh_nice(vtbl, &cmd, &saveptr) != 0)
     {
       goto errout;
     }
+#endif
 
   /* Check if any command was provided -OR- if command processing is
    * currently disabled.
@@ -806,27 +923,18 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
   /* Parse all of the arguments following the command name.  The form
    * of argv is:
    *
-   * argv[0]:      Not really used.  It is just a place hold for where the
-   *               task name would be if the same command were executed
-   *               in the "background"
-   * argv[1]:      This is string version of the vtbl needed to execute
-   *               the command (under telnetd).  It is a string because
-   *               binary values cannot be provided via char *argv[].  NOTE
-   *               that this value is filled in later.
-   * argv[2]:      The command name.  This is argv[0] when the arguments
-   *               are, finally, received by the command vtblr
-   * argv[3]:      The beginning of argument (up to NSH_MAX_ARGUMENTS)
-   * argv[argc-3]: Possibly '>' or '>>'
-   * argv[argc-2]: Possibly <file>
-   * argv[argc-1]: Possibly '&'
-   * argv[argc]:   NULL terminating pointer
+   *   argv[0]:      The command name. 
+   *   argv[1]:      The beginning of argument (up to NSH_MAX_ARGUMENTS)
+   *   argv[argc-3]: Possibly '>' or '>>'
+   *   argv[argc-2]: Possibly <file>
+   *   argv[argc-1]: Possibly '&'
+   *   argv[argc]:   NULL terminating pointer
    *
-   * Maximum size is NSH_MAX_ARGUMENTS+7
+   * Maximum size is NSH_MAX_ARGUMENTS+5
    */
 
-  argv[0] = "nsh_execute";
-  argv[2] = cmd;
-  for (argc = 3; argc < NSH_MAX_ARGUMENTS+6; argc++)
+  argv[0] = cmd;
+  for (argc = 1; argc < MAX_ARGV_ENTRIES-1; argc++)
     {
       argv[argc] = nsh_argument(vtbl, &saveptr);
       if (!argv[argc])
@@ -838,7 +946,7 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
 
   /* Check if the command should run in background */
 
-  if (argc > 3 && strcmp(argv[argc-1], "&") == 0)
+  if (argc > 1 && strcmp(argv[argc-1], "&") == 0)
     {
       vtbl->np.np_bg = TRUE;
       argv[argc-1] = NULL;
@@ -847,7 +955,7 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
 
   /* Check if the output was re-directed using > or >> */
 
-  if (argc > 5)
+  if (argc > 2)
     {
       /* Check for redirection to a new file */
 
@@ -893,30 +1001,41 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
 
   /* Check if the maximum number of arguments was exceeded */
 
-  if (argc > NSH_MAX_ARGUMENTS+3)
+  if (argc > NSH_MAX_ARGUMENTS)
     {
       nsh_output(vtbl, g_fmttoomanyargs, cmd);
     }
 
   /* Handle the case where the command is executed in background */
 
+#ifndef CONFIG_DISABLE_PTHREAD
   if (vtbl->np.np_bg)
     {
       struct sched_param param;
-      int priority;
       struct nsh_vtbl_s *bkgvtbl;
+      struct cmdarg_s *args;
+      pthread_attr_t attr;
+      pthread_t thread;
 
       /* Get a cloned copy of the vtbl with reference count=1.
        * after the command has been processed, the nsh_release() call
-       * at the end of nsh_execute() will destroy the clone.
+       * at the end of nsh_child() will destroy the clone.
        */
 
       bkgvtbl = nsh_clone(vtbl);
+      if (!bkgvtbl)
+        {
+          goto errout_with_redirect;
+        }
 
-      /* Place a string copy of the cloned vtbl in the argument list */
+      /* Create a container for the command arguments */
 
-      sprintf(strvtbl, "%p\n", bkgvtbl);
-      argv[1] = strvtbl;
+      args = nsh_cloneargs(bkgvtbl, fd, argc, argv);
+      if (!args)
+        {
+          nsh_release(bkgvtbl);
+          goto errout_with_redirect;
+        }
 
       /* Handle redirection of output via a file descriptor */
 
@@ -931,18 +1050,19 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
       if (ret != 0)
         {
           nsh_output(vtbl, g_fmtcmdfailed, cmd, "sched_getparm", NSH_ERRNO);
-          goto errout_with_redirect;
+          nsh_releaseargs(args);
+          nsh_release(bkgvtbl);
+          goto errout;
         }
 
       /* Determine the priority to execute the command */
 
-      priority = param.sched_priority;
       if (vtbl->np.np_nice != 0)
         {
-          priority -= vtbl->np.np_nice;
+          int priority = param.sched_priority - vtbl->np.np_nice;
           if (vtbl->np.np_nice < 0)
             {
-              int max_priority = sched_get_priority_max(SCHED_RR);
+              int max_priority = sched_get_priority_max(SCHED_NSH);
               if (priority > max_priority)
                 {
                   priority = max_priority;
@@ -950,55 +1070,38 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
             }
           else
             {
-              int min_priority = sched_get_priority_min(SCHED_RR);
+              int min_priority = sched_get_priority_min(SCHED_NSH);
               if (priority < min_priority)
                 {
                   priority = min_priority;
                 }
             }
+          param.sched_priority = priority;
         }
 
-      /* Execute the command as a separate task at the appropriate priority */
+      /* Set up the thread attributes */
 
-#ifndef CONFIG_CUSTOM_STACK
-      ret = task_create("nsh_execute", priority, CONFIG_EXAMPLES_NSH_STACKSIZE,
-                        nsh_execute, &argv[1]);
-#else
-      ret = task_create("nsh_execute", priority, nsh_execute, &argv[1]);
-#endif
-      if (ret < 0)
-        {
-          nsh_output(vtbl, g_fmtcmdfailed, cmd, "task_create", NSH_ERRNO);
-          goto errout_with_redirect;
-        }
-      nsh_output(vtbl, "%s [%d:%d:%d]\n", cmd, ret, priority, param.sched_priority);
+      (void)pthread_attr_init(&attr);
+      (void)pthread_attr_setschedpolicy(&attr, SCHED_NSH);
+      (void)pthread_attr_setschedparam(&attr, &param);
 
-      /* If the output was redirected, then file descriptor should
-       * be closed.  The created task has its one, independent copy of
-       * the file descriptor
-       */
+      /* Execute the command as a separate thread at the appropriate priority */
 
-      if (vtbl->np.np_redirect)
+      ret = pthread_create(&thread, &attr, nsh_child, (pthread_addr_t)args);
+      if (ret != 0)
         {
-          (void)close(fd);
+          nsh_output(vtbl, g_fmtcmdfailed, cmd, "pthread_create", ret);
+          nsh_releaseargs(args);
+          nsh_release(bkgvtbl);
+          goto errout;
         }
+      nsh_output(vtbl, "%s [%d:%d]\n", cmd, thread, param.sched_priority);
     }
   else
+#endif
     {
       ubyte save[SAVE_SIZE];
 
-      /* Increment the reference count on the vtbl.  This reference count will
-       * be decremented at the end of nsh_execute() and exists only for compatibility
-       * with the background command logic.
-       */
-
-      nsh_addref(vtbl);
-
-      /* Place a string copy of the original vtbl in the argument list */
-
-      sprintf(strvtbl, "%p\n", vtbl);
-      argv[1] = strvtbl;
-
       /* Handle redirection of output via a file descriptor */
 
       if (vtbl->np.np_redirect)
@@ -1010,7 +1113,7 @@ int nsh_parse(FAR struct nsh_vtbl_s *vtbl, char *cmdline)
        * for the next prompt.
        */
 
-      ret = nsh_execute(argc, argv);
+      ret = nsh_execute(vtbl, argc, argv);
 
       /* Restore the original output.  Undirect will close the redirection
        * file descriptor.
diff --git a/nuttx/examples/nsh/nsh_serial.c b/nuttx/examples/nsh/nsh_serial.c
index b3e60b75f..4ffcc84b2 100644
--- a/nuttx/examples/nsh/nsh_serial.c
+++ b/nuttx/examples/nsh/nsh_serial.c
@@ -1,7 +1,7 @@
 /****************************************************************************
- * examples/nsh/nsh_serial.h
+ * examples/nsh/nsh_serial.c
  *
- *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2008 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -59,7 +59,6 @@
 struct serial_s
 {
   struct nsh_vtbl_s ss_vtbl;
-  int    ss_refs;    /* Reference counts on the instance */
   int    ss_fd;      /* Re-direct file descriptor */
   FILE  *ss_stream;  /* Re-direct stream */
   char   ss_line[CONFIG_EXAMPLES_NSH_LINELEN];
@@ -75,9 +74,10 @@ struct serialsave_s
  * Private Function Prototypes
  ****************************************************************************/
 
+#ifndef CONFIG_DISABLE_PTHREAD
 static FAR struct nsh_vtbl_s *nsh_consoleclone(FAR struct nsh_vtbl_s *vtbl);
-static void nsh_consoleaddref(FAR struct nsh_vtbl_s *vtbl);
 static void nsh_consolerelease(FAR struct nsh_vtbl_s *vtbl);
+#endif
 static int nsh_consoleoutput(FAR struct nsh_vtbl_s *vtbl, const char *fmt, ...);
 static FAR char *nsh_consolelinebuffer(FAR struct nsh_vtbl_s *vtbl);
 static void nsh_consoleredirect(FAR struct nsh_vtbl_s *vtbl, int fd, FAR ubyte *save);
@@ -102,21 +102,19 @@ static void nsh_consoleexit(FAR struct nsh_vtbl_s *vtbl);
 
 static inline FAR struct serial_s *nsh_allocstruct(void)
 {
-  struct serial_s *pstate = (struct serial_s *)malloc(sizeof(struct serial_s));
+  struct serial_s *pstate = (struct serial_s *)zalloc(sizeof(struct serial_s));
   if (pstate)
     {
+#ifndef CONFIG_DISABLE_PTHREAD
       pstate->ss_vtbl.clone      = nsh_consoleclone;
-      pstate->ss_vtbl.addref     = nsh_consoleaddref;
       pstate->ss_vtbl.release    = nsh_consolerelease;
+#endif
       pstate->ss_vtbl.output     = nsh_consoleoutput;
       pstate->ss_vtbl.linebuffer = nsh_consolelinebuffer;
       pstate->ss_vtbl.redirect   = nsh_consoleredirect;
       pstate->ss_vtbl.undirect   = nsh_consoleundirect;
       pstate->ss_vtbl.exit       = nsh_consoleexit;
 
-      memset(&pstate->ss_vtbl.np, 0, sizeof(struct nsh_parser_s));
-
-      pstate->ss_refs            = 1;
       pstate->ss_fd              = 1;
       pstate->ss_stream          = stdout;
     }
@@ -225,51 +223,43 @@ static FAR char *nsh_consolelinebuffer(FAR struct nsh_vtbl_s *vtbl)
  *
  ****************************************************************************/
 
+#ifndef CONFIG_DISABLE_PTHREAD
 static FAR struct nsh_vtbl_s *nsh_consoleclone(FAR struct nsh_vtbl_s *vtbl)
 {
   FAR struct serial_s *pstate = (FAR struct serial_s *)vtbl;
   FAR struct serial_s *pclone = nsh_allocstruct();
-  pclone->ss_fd     = pstate->ss_fd;
-  pclone->ss_stream = NULL;
-  return &pclone->ss_vtbl;
-}
-
-/****************************************************************************
- * Name: nsh_consoleaddref
- *
- * Description:
- *   Increment the reference count on the vtbl.
- *
- ****************************************************************************/
 
-static void nsh_consoleaddref(FAR struct nsh_vtbl_s *vtbl)
-{
-  FAR struct serial_s *pstate = (FAR struct serial_s *)vtbl;
-  pstate->ss_refs++;
+  if (pclone->ss_fd == 1)
+    {
+      pclone->ss_fd     = 1;
+      pclone->ss_stream = stdout;
+    }
+  else
+    {
+      pclone->ss_fd     = pstate->ss_fd;
+      pclone->ss_stream = NULL;
+    }
+  return &pclone->ss_vtbl;
 }
+#endif
 
 /****************************************************************************
  * Name: nsh_consolerelease
  *
  * Description:
- *   Decrement the reference count on the vtbl, releasing it when the count
- *   decrements to zero.
+ *   Release the cloned instance
  *
  ****************************************************************************/
 
+#ifndef CONFIG_DISABLE_PTHREAD
 static void nsh_consolerelease(FAR struct nsh_vtbl_s *vtbl)
 {
   FAR struct serial_s *pstate = (FAR struct serial_s *)vtbl;
-  if (pstate->ss_refs > 1)
-    {
-      pstate->ss_refs--;
-    }
-  else
-    {
-      nsh_closeifnotclosed(pstate);
-      free(vtbl);
-    }
+
+  nsh_closeifnotclosed(pstate);
+  free(vtbl);
 }
+#endif
 
 /****************************************************************************
  * Name: nsh_consoleredirect
diff --git a/nuttx/examples/nsh/nsh_telnetd.c b/nuttx/examples/nsh/nsh_telnetd.c
index 5cfe7ba50..9699aa651 100644
--- a/nuttx/examples/nsh/nsh_telnetd.c
+++ b/nuttx/examples/nsh/nsh_telnetd.c
@@ -51,7 +51,9 @@
 #include <stdarg.h>
 #include <string.h>
 #include <pthread.h>
+#include <semaphore.h>
 #include <assert.h>
+#include <errno.h>
 #include <debug.h>
 
 #include <net/if.h>
@@ -59,6 +61,8 @@
 
 #include "nsh.h"
 
+#ifdef CONFIG_EXAMPLES_NSH_TELNET
+
 /****************************************************************************
  * Definitions
  ****************************************************************************/
@@ -86,10 +90,13 @@
 
 struct telnetio_s
 {
+  sem_t  tio_sem;
+  pid_t  tio_holder;
   int    tio_sockfd;
   uint16 tio_sndlen;
   uint8  tio_bufndx;
   uint8  tio_state;
+  uint8  tio_semnest;
   char   tio_buffer[CONFIG_EXAMPLES_NSH_IOBUFFER_SIZE];
 };
 
@@ -113,7 +120,6 @@ struct telnetd_s
 {
   struct nsh_vtbl_s tn_vtbl;
   boolean           tn_redirected;
-  int               tn_refs;    /* Reference counts on the instance */
   union
     {
       struct telnetio_s *tn;
@@ -127,7 +133,6 @@ struct telnetd_s
  ****************************************************************************/
 
 static FAR struct nsh_vtbl_s *nsh_telnetclone(FAR struct nsh_vtbl_s *vtbl);
-static void nsh_telnetaddref(FAR struct nsh_vtbl_s *vtbl);
 static void nsh_telnetrelease(FAR struct nsh_vtbl_s *vtbl);
 static int nsh_telnetoutput(FAR struct nsh_vtbl_s *vtbl, const char *fmt, ...);
 static int nsh_redirectoutput(FAR struct nsh_vtbl_s *vtbl, const char *fmt, ...);
@@ -141,6 +146,72 @@ static void nsh_telnetexit(FAR struct nsh_vtbl_s *vtbl);
  ****************************************************************************/
 
 /****************************************************************************
+ * Name: tio_semtake
+ ****************************************************************************/
+
+static void tio_semtake(struct telnetio_s *tio)
+{
+  pid_t my_pid = getpid();
+
+  /* Does this task already have the semaphore? */
+
+  if (tio->tio_holder == my_pid)
+    {
+      /* Yes, just increment the number of references that the task holds */
+
+      tio->tio_semnest++;
+    }
+  else
+    {
+      /* No, Take the semaphore (perhaps waiting) */
+
+      while (sem_wait(&tio->tio_sem) != 0)
+        {
+          /* The only case that an error should occur here is if the wait was
+           * awakened by a signal.
+           */
+
+          ASSERT(errno == EINTR);
+        }
+
+      /* Stake the claim and return */
+
+      tio->tio_holder  = my_pid;
+      tio->tio_semnest = 1;
+    }
+}
+
+/****************************************************************************
+ * Name: tio_semgive
+ ****************************************************************************/
+
+static void tio_semgive(struct telnetio_s *tio)
+{
+  pid_t my_pid = getpid();
+
+  /* I better be holding at least one count on the semaphore */
+
+  ASSERT(tio->tio_holder == my_pid);
+
+  /* Do I hold multiple references to the semphore */
+
+  if (tio->tio_semnest > 1)
+    {
+      /* Yes, just release one count and return */
+
+      tio->tio_semnest--;
+    }
+  else
+    {
+      /* Nope, this is the last reference I have */
+
+      tio->tio_holder = -1;
+      tio->tio_semnest = 0;
+      ASSERT(sem_post(&tio->tio_sem) == 0);
+    }
+}
+
+/****************************************************************************
  * Name: nsh_dumpbuffer
  *
  * Description:
@@ -196,22 +267,16 @@ static void nsh_dumpbuffer(const char *msg, const char *buffer, ssize_t nbytes)
 
 static FAR struct telnetd_s *nsh_allocstruct(void)
 {
-  struct telnetd_s *pstate = (struct telnetd_s *)malloc(sizeof(struct telnetd_s));
+  struct telnetd_s *pstate = (struct telnetd_s *)zalloc(sizeof(struct telnetd_s));
   if (pstate)
     {
-      memset(pstate, 0, sizeof(struct telnetd_s));
       pstate->tn_vtbl.clone      = nsh_telnetclone;
-      pstate->tn_vtbl.addref     = nsh_telnetaddref;
       pstate->tn_vtbl.release    = nsh_telnetrelease;
       pstate->tn_vtbl.output     = nsh_telnetoutput;
       pstate->tn_vtbl.linebuffer = nsh_telnetlinebuffer;
       pstate->tn_vtbl.redirect   = nsh_telnetredirect;
       pstate->tn_vtbl.undirect   = nsh_telnetundirect;
       pstate->tn_vtbl.exit       = nsh_telnetexit;
-
-      memset(&pstate->tn_vtbl.np, 0, sizeof(struct nsh_parser_s));
-
-      pstate->tn_refs            = 1;
     }
   return pstate;
 }
@@ -275,6 +340,9 @@ static void nsh_closeifnotclosed(struct telnetd_s *pstate)
  * Description:
  *   Add another parsed character to the TELNET command string
  *
+ * Assumption:
+ *   Caller holds TIO semaphore
+ *
  ****************************************************************************/
 
 static void nsh_putchar(struct telnetd_s *pstate, uint8 ch)
@@ -327,7 +395,7 @@ static void nsh_sendopt(struct telnetd_s *pstate, uint8 option, uint8 value)
   nsh_dumpbuffer("Send optbuf", optbuf, 4);
   if (send(tio->tio_sockfd, optbuf, 4, 0) < 0)
     {
-      dbg("[%d] Failed to send TELNET_IAC\n", tio->tio_sockfd);
+      dbg("[%d] Failed to send TELNET_IAC: %d\n", tio->tio_sockfd, errno);
     }
 }
 
@@ -343,15 +411,17 @@ static void nsh_flush(FAR struct telnetd_s *pstate)
 {
   struct telnetio_s *tio = pstate->u.tn;
 
+  tio_semtake(tio);
   if (tio->tio_sndlen > 0)
     {
       nsh_dumpbuffer("Shell output", tio->tio_buffer, tio->tio_sndlen);
       if (send(tio->tio_sockfd, tio->tio_buffer, tio->tio_sndlen, 0) < 0)
         {
-          dbg("[%d] Failed to send response\n", tio->tio_sockfd);
+          dbg("[%d] Failed to send response: %d\n", tio->tio_sockfd, errno);
         }
     }
   tio->tio_sndlen = 0;
+  tio_semgive(tio);
 }
 
 /****************************************************************************
@@ -368,6 +438,7 @@ static int nsh_receive(struct telnetd_s *pstate, size_t len)
   char              *ptr = tio->tio_buffer;
   uint8 ch;
 
+  tio_semtake(tio);
   while (len > 0)
     {
       ch = *ptr++;
@@ -449,6 +520,7 @@ static int nsh_receive(struct telnetd_s *pstate, size_t len)
             break;
         }
     }
+  tio_semgive(tio);
   return OK;
 }
 
@@ -465,7 +537,7 @@ static int nsh_receive(struct telnetd_s *pstate, size_t len)
 static void *nsh_connection(void *arg)
 {
   struct telnetd_s  *pstate = nsh_allocstruct();
-  struct telnetio_s *tio    = (struct telnetio_s *)malloc(sizeof(struct telnetio_s));
+  struct telnetio_s *tio    = (struct telnetio_s *)zalloc(sizeof(struct telnetio_s));
   int                sockfd = (int)arg;
   int                ret    = ERROR;
 
@@ -477,7 +549,7 @@ static void *nsh_connection(void *arg)
     {
       /* Initialize the thread state structure */
 
-      memset(tio, 0, sizeof(struct telnetio_s));
+      sem_init(&tio->tio_sem, 0, 1);
       tio->tio_sockfd = sockfd;
       tio->tio_state  = STATE_NORMAL;
       pstate->u.tn    = tio;
@@ -503,7 +575,7 @@ static void *nsh_connection(void *arg)
 
               /* Process the received TELNET data */
 
-              nsh_dumpbuffer("Received buffer", pstate->u.tn.tio_buffer, ret);
+              nsh_dumpbuffer("Received buffer", tio->tio_buffer, ret);
               ret = nsh_receive(pstate, ret);
             }
         }
@@ -522,6 +594,7 @@ static void *nsh_connection(void *arg)
 
   if (tio)
     {
+      sem_destroy(&tio->tio_sem);
       free(tio);
     }
 
@@ -550,6 +623,8 @@ static int nsh_telnetoutput(FAR struct nsh_vtbl_s *vtbl, const char *fmt, ...)
   int                len;
   va_list            ap;
 
+  tio_semtake(tio);
+
   /* Put the new info into the buffer.  Here we are counting on the fact that
    * no output strings will exceed CONFIG_EXAMPLES_NSH_LINELEN!
    */
@@ -582,6 +657,7 @@ static int nsh_telnetoutput(FAR struct nsh_vtbl_s *vtbl, const char *fmt, ...)
    * maximum length string.
    */
 
+  tio_semgive(tio);
   if (nbytes > CONFIG_EXAMPLES_NSH_IOBUFFER_SIZE - CONFIG_EXAMPLES_NSH_LINELEN)
     {
       nsh_flush(pstate);
@@ -613,11 +689,11 @@ static int nsh_redirectoutput(FAR struct nsh_vtbl_s *vtbl, const char *fmt, ...)
    {
      return ERROR;
    }
- 
+
   va_start(ap, fmt);
   ret = vfprintf(pstate->u.rd.rd_stream, fmt, ap);
   va_end(ap);
- 
+
   return ret;
 }
 
@@ -645,52 +721,49 @@ static FAR char *nsh_telnetlinebuffer(FAR struct nsh_vtbl_s *vtbl)
 
 static FAR struct nsh_vtbl_s *nsh_telnetclone(FAR struct nsh_vtbl_s *vtbl)
 {
-  FAR struct telnetd_s *pstate = (FAR struct telnetd_s *)vtbl;
-  FAR struct telnetd_s *pclone = nsh_allocstruct();
-
-  pclone->tn_redirected  = TRUE;
-  pclone->tn_vtbl.output = nsh_redirectoutput;
-  pclone->u.rd.rd_fd     = pstate->u.rd.rd_fd;
-  pclone->u.rd.rd_stream = NULL;
-  return &pclone->tn_vtbl;
-}
-
-/****************************************************************************
- * Name: nsh_telnetaddref
- *
- * Description:
- *   Increment the reference count on the vtbl.
- *
- ****************************************************************************/
+  FAR struct telnetd_s  *pstate = (FAR struct telnetd_s *)vtbl;
+  FAR struct telnetd_s  *pclone = nsh_allocstruct();
+  FAR struct nsh_vtbl_s *ret    = NULL;
 
-static void nsh_telnetaddref(FAR struct nsh_vtbl_s *vtbl)
-{
-  FAR struct telnetd_s *pstate = (FAR struct telnetd_s *)vtbl;
-  pstate->tn_refs++;
+  if (pclone)
+    {
+      if (pstate->tn_redirected)
+        {
+          pclone->tn_redirected  = TRUE;
+          pclone->tn_vtbl.output = nsh_redirectoutput;
+          pclone->u.rd.rd_fd     = pstate->u.rd.rd_fd;
+          pclone->u.rd.rd_stream = NULL;
+        }
+      else
+        {
+          pclone->u.tn = pstate->u.tn;
+        }
+      ret = &pclone->tn_vtbl;
+    }
+  return ret;
 }
 
 /****************************************************************************
  * Name: nsh_telnetrelease
  *
  * Description:
- *   Decrement the reference count on the vtbl, releasing it when the count
- *   decrements to zero.
+ *   Release the cloned instance
  *
  ****************************************************************************/
 
 static void nsh_telnetrelease(FAR struct nsh_vtbl_s *vtbl)
 {
   FAR struct telnetd_s *pstate = (FAR struct telnetd_s *)vtbl;
-  if (pstate->tn_refs > 1)
+
+  if (pstate->tn_redirected)
     {
-      pstate->tn_refs--;
+      nsh_closeifnotclosed(pstate);
     }
   else
     {
-      DEBUGASSERT(pstate->tn_redirected);
-      nsh_closeifnotclosed(pstate);
-      free(vtbl);
+      nsh_flush(pstate);
     }
+  free(pstate);
 }
 
 /****************************************************************************
@@ -768,7 +841,7 @@ static void nsh_telnetexit(FAR struct nsh_vtbl_s *vtbl)
  ****************************************************************************/
 
 /****************************************************************************
- * Name: nsh_main
+ * Name: nsh_telnetmain
  *
  * Description:
  *   This is the main processing thread for telnetd.  It never returns
@@ -857,3 +930,5 @@ int nsh_telnetmain(int argc, char *argv[])
   uip_server(HTONS(23), nsh_connection, CONFIG_EXAMPLES_NSH_STACKSIZE);
   return OK;
 }
+
+#endif /* CONFIG_EXAMPLES_NSH_TELNET */