/********************************************************************************
 * include/nuttx/sched.h
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ********************************************************************************/

#ifndef __INCLUDE_NUTTX_SCHED_H
#define __INCLUDE_NUTTX_SCHED_H

/********************************************************************************
 * Included Files
 ********************************************************************************/

#include <nuttx/config.h>

#include <sys/types.h>
#include <stdint.h>
#include <queue.h>
#include <signal.h>
#include <semaphore.h>
#include <pthread.h>
#include <mqueue.h>
#include <time.h>

#include <nuttx/clock.h>
#include <nuttx/irq.h>
#include <nuttx/wdog.h>
#include <nuttx/mm/shm.h>
#include <nuttx/fs/fs.h>
#include <nuttx/net/net.h>

#include <arch/arch.h>

/********************************************************************************
 * Pre-processor Definitions
 ********************************************************************************/

/* Configuration ****************************************************************/

/* Task groups currently only supported for retention of child status */

#undef HAVE_GROUP_MEMBERS

/* We need a group an group members if we are supporting the parent/child
 * relationship.
 */

#if defined(CONFIG_SCHED_HAVE_PARENT) && defined(CONFIG_SCHED_CHILD_STATUS)
#  define HAVE_GROUP_MEMBERS  1
#endif

/* We don't need group members if support for pthreads is disabled */

#ifdef CONFIG_DISABLE_PTHREAD
#  undef HAVE_GROUP_MEMBERS
#endif

/* Sporadic scheduling */

#ifndef CONFIG_SCHED_SPORADIC_MAXREPL
#  define CONFIG_SCHED_SPORADIC_MAXREPL 3
#endif

/* Task Management Definitions **************************************************/

/* Special task IDS.  Any negative PID is invalid. */

#define NULL_TASK_PROCESS_ID       (pid_t)0
#define INVALID_PROCESS_ID         (pid_t)-1

/* This is the maximum number of times that a lock can be set */

#define MAX_LOCK_COUNT             127

/* Values for the struct tcb_s flags bits */

#define TCB_FLAG_TTYPE_SHIFT       (0)                           /* Bits 0-1: thread type */
#define TCB_FLAG_TTYPE_MASK        (3 << TCB_FLAG_TTYPE_SHIFT)
#  define TCB_FLAG_TTYPE_TASK      (0 << TCB_FLAG_TTYPE_SHIFT)   /*   Normal user task */
#  define TCB_FLAG_TTYPE_PTHREAD   (1 << TCB_FLAG_TTYPE_SHIFT)   /*   User pthread */
#  define TCB_FLAG_TTYPE_KERNEL    (2 << TCB_FLAG_TTYPE_SHIFT)   /*   Kernel thread */
#define TCB_FLAG_NONCANCELABLE     (1 << 2)                      /* Bit 2: Pthread is non-cancelable */
#define TCB_FLAG_CANCEL_DEFERRED   (1 << 3)                      /* Bit 3: Deferred (vs asynch) cancellation type */
#define TCB_FLAG_CANCEL_PENDING    (1 << 4)                      /* Bit 4: Pthread cancel is pending */
#define TCB_FLAG_POLICY_SHIFT      (5)                           /* Bit 5-6: Scheduling policy */
#define TCB_FLAG_POLICY_MASK       (3 << TCB_FLAG_POLICY_SHIFT)
#  define TCB_FLAG_SCHED_FIFO      (0 << TCB_FLAG_POLICY_SHIFT)  /* FIFO scheding policy */
#  define TCB_FLAG_SCHED_RR        (1 << TCB_FLAG_POLICY_SHIFT)  /* Round robin scheding policy */
#  define TCB_FLAG_SCHED_SPORADIC  (2 << TCB_FLAG_POLICY_SHIFT)  /* Sporadic scheding policy */
#  define TCB_FLAG_SCHED_OTHER     (3 << TCB_FLAG_POLICY_SHIFT)  /* Other scheding policy */
#define TCB_FLAG_CPU_LOCKED        (1 << 7)                      /* Bit 7: Locked to this CPU */
#define TCB_FLAG_SIGNAL_ACTION     (1 << 8)                      /* Bit 8: In a signal handler */
#define TCB_FLAG_SYSCALL           (1 << 9)                      /* Bit 9: In a system call */
#define TCB_FLAG_EXIT_PROCESSING   (1 << 10)                     /* Bit 10: Exitting */
                                                                 /* Bits 11-15: Available */

/* Values for struct task_group tg_flags */

#define GROUP_FLAG_NOCLDWAIT       (1 << 0)                      /* Bit 0: Do not retain child exit status */
#define GROUP_FLAG_ADDRENV         (1 << 1)                      /* Bit 1: Group has an address environment */
#define GROUP_FLAG_PRIVILEGED      (1 << 2)                      /* Bit 2: Group is privileged */
#define GROUP_FLAG_DELETED         (1 << 3)                      /* Bit 3: Group has been deleted but not yet freed */
                                                                 /* Bits 4-7: Available */

/* Values for struct child_status_s ch_flags */

#define CHILD_FLAG_TTYPE_SHIFT     (0)                           /* Bits 0-1: child thread type */
#define CHILD_FLAG_TTYPE_MASK      (3 << CHILD_FLAG_TTYPE_SHIFT)
#  define CHILD_FLAG_TTYPE_TASK    (0 << CHILD_FLAG_TTYPE_SHIFT) /* Normal user task */
#  define CHILD_FLAG_TTYPE_PTHREAD (1 << CHILD_FLAG_TTYPE_SHIFT) /* User pthread */
#  define CHILD_FLAG_TTYPE_KERNEL  (2 << CHILD_FLAG_TTYPE_SHIFT) /* Kernel thread */
#define CHILD_FLAG_EXITED          (1 << 2)                      /* Bit 2: The child thread has exit'ed */
                                                                 /* Bits 3-7: Available */

/* Sporadic scheduler flags */

#define SPORADIC_FLAG_ALLOCED      (1 << 0)                      /* Bit 0: Timer is allocated */
#define SPORADIC_FLAG_MAIN         (1 << 1)                      /* Bit 1: The main timer */
#define SPORADIC_FLAG_REPLENISH    (1 << 2)                      /* Bit 2: Replenishment cycle */
                                                                 /* Bits 3-7: Available */

/* Most internal nxsched_* interfaces are not available in the user space in
 * PROTECTED and KERNEL builds.  In that context, the application semaphore
 * interfaces must be used.  The differences between the two sets of
 * interfaces are:  (1) the nxsched_* interfaces do not cause cancellation
 * points and (2) they do not modify the errno variable.
 *
 * This is only important when compiling libraries (libc or libnx) that are
 * used both by the OS (libkc.a and libknx.a) or by the applications
 * (libc.a and libnx.a).  In that case, the correct interface must be
 * used for the build context.
 *
 * REVISIT:  In the flat build, the same functions must be used both by
 * the OS and by applications.  We have to use the normal user functions
 * in this case or we will fail to set the errno or fail to create the
 * cancellation point.
 */

#if !defined(CONFIG_BUILD_FLAT) && defined(__KERNEL__)
#  define _SCHED_GETPARAM(t,p)       nxsched_get_param(t,p)
#  define _SCHED_SETPARAM(t,p)       nxsched_set_param(t,p)
#  define _SCHED_GETSCHEDULER(t)     nxsched_get_scheduler(t)
#  define _SCHED_SETSCHEDULER(t,s,p) nxsched_set_scheduler(t,s,p)
#  define _SCHED_GETAFFINITY(t,c,m)  nxsched_get_affinity(t,c,m)
#  define _SCHED_SETAFFINITY(t,c,m)  nxsched_set_affinity(t,c,m)
#  define _SCHED_ERRNO(r)            (-(r))
#  define _SCHED_ERRVAL(r)           (r)
#else
#  define _SCHED_GETPARAM(t,p)       sched_getparam(t,p)
#  define _SCHED_SETPARAM(t,p)       sched_setparam(t,p)
#  define _SCHED_GETSCHEDULER(t)     sched_getscheduler(t)
#  define _SCHED_SETSCHEDULER(t,s,p) sched_setscheduler(t,s,p)
#  define _SCHED_GETAFFINITY(t,c,m)  sched_getaffinity(t,c,m)
#  define _SCHED_SETAFFINITY(t,c,m)  sched_setaffinity(t,c,m)
#  define _SCHED_ERRNO(r)            errno
#  define _SCHED_ERRVAL(r)           (-errno)
#endif

/* The number of callback can be saved */

#if defined(CONFIG_SCHED_ONEXIT_MAX)
#  define CONFIG_SCHED_EXIT_MAX CONFIG_SCHED_ONEXIT_MAX
#elif defined(CONFIG_SCHED_ATEXIT_MAX)
#  define CONFIG_SCHED_EXIT_MAX CONFIG_SCHED_ATEXIT_MAX
#endif

#if defined(CONFIG_SCHED_EXIT_MAX) && CONFIG_SCHED_EXIT_MAX < 1
#  error "CONFIG_SCHED_EXIT_MAX < 1"
#endif

/********************************************************************************
 * Public Type Definitions
 ********************************************************************************/

#ifndef __ASSEMBLY__

/* General Task Management Types ************************************************/

/* This is the type of the task_state field of the TCB. NOTE: the order and
 * content of this enumeration is critical since there are some OS tables indexed
 * by these values.  The range of values is assumed to fit into a uint8_t in
 * struct tcb_s.
 */

enum tstate_e
{
  TSTATE_TASK_INVALID    = 0, /* INVALID      - The TCB is uninitialized */
  TSTATE_TASK_PENDING,        /* READY_TO_RUN - Pending preemption unlock */
  TSTATE_TASK_READYTORUN,     /* READY-TO-RUN - But not running */
#ifdef CONFIG_SMP
  TSTATE_TASK_ASSIGNED,       /* READY-TO-RUN - Not running, but assigned to a CPU */
#endif
  TSTATE_TASK_RUNNING,        /* READY_TO_RUN - And running */

  TSTATE_TASK_INACTIVE,       /* BLOCKED      - Initialized but not yet activated */
  TSTATE_WAIT_SEM,            /* BLOCKED      - Waiting for a semaphore */
  TSTATE_WAIT_SIG,            /* BLOCKED      - Waiting for a signal */
#ifndef CONFIG_DISABLE_MQUEUE
  TSTATE_WAIT_MQNOTEMPTY,     /* BLOCKED      - Waiting for a MQ to become not empty. */
  TSTATE_WAIT_MQNOTFULL,      /* BLOCKED      - Waiting for a MQ to become not full. */
#endif
#ifdef CONFIG_PAGING
  TSTATE_WAIT_PAGEFILL,       /* BLOCKED      - Waiting for page fill */
#endif
#ifdef CONFIG_SIG_SIGSTOP_ACTION
  TSTATE_TASK_STOPPED,        /* BLOCKED      - Waiting for SIGCONT */
#endif

  NUM_TASK_STATES             /* Must be last */
};

typedef enum tstate_e tstate_t;

/* The following definitions are determined by tstate_t.  Ordering of values
 * in the enumeration is important!
 */

#define FIRST_READY_TO_RUN_STATE   TSTATE_TASK_READYTORUN
#define LAST_READY_TO_RUN_STATE    TSTATE_TASK_RUNNING
#define FIRST_ASSIGNED_STATE       TSTATE_TASK_ASSIGNED
#define LAST_ASSIGNED_STATE        TSTATE_TASK_RUNNING
#define FIRST_BLOCKED_STATE        TSTATE_TASK_INACTIVE
#define LAST_BLOCKED_STATE         (NUM_TASK_STATES-1)

/* The following is the form of a thread start-up function */

typedef CODE void (*start_t)(void);

/* This is the entry point into the main thread of the task or into a created
 * pthread within the task.
 */

union entry_u
{
  pthread_startroutine_t pthread;
  main_t main;
};

typedef union entry_u entry_t;

/* This is the type of the function called at task startup */

#ifdef CONFIG_SCHED_STARTHOOK
typedef CODE void (*starthook_t)(FAR void *arg);
#endif

/* These are the types of the functions that are executed with exit() is called
 * (if registered via atexit() on on_exit()).
 */

#ifdef CONFIG_SCHED_ATEXIT
typedef CODE void (*atexitfunc_t)(void);
#endif

#ifdef CONFIG_SCHED_ONEXIT
typedef CODE void (*onexitfunc_t)(int exitcode, FAR void *arg);
#endif

/* struct sporadic_s ************************************************************/

#ifdef CONFIG_SCHED_SPORADIC

/* This structure represents one replenishment interval.  This is what is
 * received by each timeout handler.
 */

struct sporadic_s;
struct replenishment_s
{
  FAR struct tcb_s *tcb;            /* The parent TCB structure                 */
  struct wdog_s timer;              /* Timer dedicated to this interval         */
  uint32_t budget;                  /* Current budget time                      */
  uint8_t  flags;                   /* See SPORADIC_FLAG_* definitions          */
};

/* This structure is an allocated "plug-in" to the main TCB structure.  It is
 * allocated when the sporadic scheduling policy is assigned to a thread.  Thus,
 * in the context of numerous threads of varying policies, there the overhead
 * from this significant allocation is only borne by the threads with the
 * sporadic scheduling policy.
 */

struct sporadic_s
{
  bool      suspended;              /* Thread is currently suspended            */
  uint8_t   hi_priority;            /* Sporadic high priority                   */
  uint8_t   low_priority;           /* Sporadic low priority                    */
  uint8_t   max_repl;               /* Maximum number of replenishments         */
  uint8_t   nrepls;                 /* Number of active replenishments          */
  uint32_t  repl_period;            /* Sporadic replenishment period            */
  uint32_t  budget;                 /* Sporadic execution budget period         */
  clock_t   eventtime;              /* Time thread suspended or [re-]started    */

  /* This is the last interval timer activated */

  FAR struct replenishment_s *active;

  /* This is the list of replenishment interval timers */

  struct replenishment_s replenishments[CONFIG_SCHED_SPORADIC_MAXREPL];
};

#endif /* CONFIG_SCHED_SPORADIC */

/* struct child_status_s ********************************************************/

/* This structure is used to maintain information about child tasks.  pthreads
 * work differently, they have join information.  This is only for child tasks.
 */

#ifdef CONFIG_SCHED_CHILD_STATUS
struct child_status_s
{
  FAR struct child_status_s *flink;

  uint8_t ch_flags;                 /* Child status:  See CHILD_FLAG_* defns     */
  pid_t   ch_pid;                   /* Child task ID                             */
  int     ch_status;                /* Child exit status                         */
};
#endif

/* struct pthread_cleanup_s *****************************************************/

/* This structure describes one element of the pthread cleanup stack */

#ifdef CONFIG_PTHREAD_CLEANUP
struct pthread_cleanup_s
{
  pthread_cleanup_t pc_cleaner;     /* Cleanup callback address */
  FAR void *pc_arg;                 /* Argument that accompanies the callback */
};
#endif

/* type tls_ndxset_t ************************************************************/

/* Smallest addressable type that can hold the entire configured number of TLS
 * data indexes.
 */

#if CONFIG_TLS_NELEM > 0
#  if CONFIG_TLS_NELEM > 32
#    error Too many TLS elements
#  elif CONFIG_TLS_NELEM > 16
     typedef uint32_t tls_ndxset_t;
#  elif CONFIG_TLS_NELEM > 8
     typedef uint16_t tls_ndxset_t;
#  else
     typedef uint8_t tls_ndxset_t;
#  endif
#endif

/* type grpid_t *****************************************************************/

/* The task group ID */

typedef int16_t grpid_t;

/* struct dspace_s **************************************************************/

/* This structure describes a reference counted D-Space region.  This must be a
 * separately allocated "break-away" structure that can be owned by a task and
 * any pthreads created by the task.
 */

#ifdef CONFIG_PIC
struct dspace_s
{
  /* The life of the structure allocation is determined by this reference
   * count.  This count is number of threads that shared the same D-Space.
   * This includes the parent task as well as any pthreads created by the
   * parent task or any of its child threads.
   */

  uint16_t crefs;

  /* This is the allocated D-Space memory region.  This may be a physical
   * address allocated with kmm_malloc(), or it may be virtual address associated
   * with an address environment (if CONFIG_ARCH_ADDRENV=y).
   */

  FAR uint8_t *region;
};
#endif

/* struct stackinfo_s ***********************************************************/

/* Used to report stack information */

struct stackinfo_s
{
  size_t    adj_stack_size;              /* Stack size after adjustment         */
                                         /* for hardware, processor, etc.       */
                                         /* (for debug purposes only)           */
  FAR void *stack_alloc_ptr;             /* Pointer to allocated stack          */
                                         /* Needed to deallocate stack          */
  FAR void *adj_stack_ptr;               /* Adjusted stack_alloc_ptr for HW     */
                                         /* The initial stack pointer value     */
};

/* struct exitinfo_s ************************************************************/

struct exitinfo_s
{
  union
  {
#ifdef CONFIG_SCHED_ATEXIT
    atexitfunc_t at;
#endif
#ifdef CONFIG_SCHED_ONEXIT
    onexitfunc_t on;
#endif
  } func;
#ifdef CONFIG_SCHED_ONEXIT
  FAR void *arg;
#endif
};

/* struct task_group_s **********************************************************/

/* All threads created by pthread_create belong in the same task group (along
 * with the thread of the original task).  struct task_group_s is a shared
 * structure referenced by the TCB of each thread that is a member of the task
 * group.
 *
 * This structure should contain *all* resources shared by tasks and threads that
 * belong to the same task group:
 *
 *   Child exit status
 *   Environment variables
 *   PIC data space and address environments
 *   File descriptors
 *   FILE streams
 *   Sockets
 *   Address environments.
 *
 * Each instance of struct task_group_s is reference counted. Each instance is
 * created with a reference count of one.  The reference incremented when each
 * thread joins the group and decremented when each thread exits, leaving the
 * group.  When the reference count decrements to zero, the struct task_group_s
 * is free.
 */

#ifndef CONFIG_DISABLE_PTHREAD
struct join_s;                      /* Forward reference                        */
                                    /* Defined in sched/pthread/pthread.h       */
#endif
#ifdef CONFIG_BINFMT_LOADABLE
struct binary_s;                    /* Forward reference                        */
                                    /* Defined in include/nuttx/binfmt/binfmt.h */
#endif

struct task_group_s
{
#if defined(HAVE_GROUP_MEMBERS) || defined(CONFIG_ARCH_ADDRENV)
  struct task_group_s *flink;       /* Supports a singly linked list            */
  grpid_t tg_grpid;                 /* The ID of this task group                */
#endif
#ifdef HAVE_GROUP_MEMBERS
  grpid_t tg_pgrpid;                /* The ID of the parent task group          */
#endif
#if !defined(CONFIG_DISABLE_PTHREAD) && defined(CONFIG_SCHED_HAVE_PARENT)
  pid_t tg_task;                    /* The ID of the task within the group      */
#endif
  uint8_t tg_flags;                 /* See GROUP_FLAG_* definitions             */

  /* User identity **************************************************************/

#ifdef CONFIG_SCHED_USER_IDENTITY
  uid_t   tg_uid;                   /* User identity                            */
  gid_t   tg_gid;                   /* User group identity                      */
#endif

  /* Group membership ***********************************************************/

  uint8_t    tg_nmembers;           /* Number of members in the group           */
#ifdef HAVE_GROUP_MEMBERS
  uint8_t    tg_mxmembers;          /* Number of members in allocation          */
  FAR pid_t *tg_members;            /* Members of the group                     */
#endif

  /* [at|on]exit support ********************************************************/

#ifdef CONFIG_SCHED_EXIT_MAX
  struct exitinfo_s tg_exit[CONFIG_SCHED_EXIT_MAX];
#endif

#ifdef CONFIG_BINFMT_LOADABLE
  /* Loadable module support ****************************************************/

  FAR struct binary_s *tg_bininfo;  /* Describes resources used by program      */
#endif

#ifdef CONFIG_SCHED_HAVE_PARENT
  /* Child exit status **********************************************************/

#ifdef CONFIG_SCHED_CHILD_STATUS
  FAR struct child_status_s *tg_children; /* Head of a list of child status     */
#endif

#ifndef HAVE_GROUP_MEMBERS
  /* REVISIT: What if parent thread exits?  Should use tg_pgrpid. */

  pid_t    tg_ppid;                 /* This is the ID of the parent thread      */
#ifndef CONFIG_SCHED_CHILD_STATUS
  uint16_t tg_nchildren;            /* This is the number active children       */
#endif
#endif /* HAVE_GROUP_MEMBERS */
#endif /* CONFIG_SCHED_HAVE_PARENT */

#if defined(CONFIG_SCHED_WAITPID) && !defined(CONFIG_SCHED_HAVE_PARENT)
  /* waitpid support ************************************************************/

  /* Simple mechanism used only when there is no support for SIGCHLD            */

  uint8_t tg_nwaiters;              /* Number of waiters                        */
  uint8_t tg_waitflags;             /* User flags for waitpid behavior          */
  sem_t tg_exitsem;                 /* Support for waitpid                      */
  FAR int *tg_statloc;              /* Location to return exit status           */
#endif

#ifndef CONFIG_DISABLE_PTHREAD
  /* Pthreads *******************************************************************/

                                    /* Pthread join Info:                       */

  sem_t tg_joinsem;                 /*   Mutually exclusive access to join data */
  FAR struct join_s *tg_joinhead;   /*   Head of a list of join data            */
  FAR struct join_s *tg_jointail;   /*   Tail of a list of join data            */
#endif

  /* Thread local storage *******************************************************/

#if CONFIG_TLS_NELEM > 0
  tls_ndxset_t tg_tlsset;           /* Set of TLS data indexes allocated        */
#endif

  /* POSIX Signal Control Fields ************************************************/

  sq_queue_t tg_sigactionq;         /* List of actions for signals              */
  sq_queue_t tg_sigpendingq;        /* List of pending signals                  */
#ifdef CONFIG_SIG_DEFAULT
  sigset_t tg_sigdefault;           /* Set of signals set to the default action */
#endif

#ifndef CONFIG_DISABLE_ENVIRON
  /* Environment variables ******************************************************/

  size_t     tg_envsize;            /* Size of environment string allocation    */
  FAR char  *tg_envp;               /* Allocated environment strings            */
#endif

#ifndef CONFIG_DISABLE_POSIX_TIMERS
  /* Interval timer *************************************************************/

  timer_t itimer;
#endif

  /* PIC data space and address environments ************************************/

  /* Logically the PIC data space belongs here (see struct dspace_s).  The
   * current logic needs review:  There are differences in the away that the
   * life of the PIC data is managed.
   */

  /* File descriptors ***********************************************************/

  struct filelist tg_filelist;      /* Maps file descriptor to file             */

#if CONFIG_NFILE_STREAMS > 0
  /* FILE streams ***************************************************************/

  /* In a flat, single-heap build.  The stream list is allocated with this
   * structure.  But kernel mode with a kernel allocator, it must be separately
   * allocated using a user-space allocator.
   */

#ifdef CONFIG_MM_KERNEL_HEAP
  FAR struct streamlist *tg_streamlist;
#else
  struct streamlist tg_streamlist;  /* Holds C buffered I/O info                */
#endif
#endif

#ifdef CONFIG_NET
  /* Sockets ********************************************************************/

  struct socketlist tg_socketlist;  /* Maps socket descriptor to socket         */
#endif

#ifndef CONFIG_DISABLE_MQUEUE
  /* POSIX Named Message Queue Fields *******************************************/

  sq_queue_t tg_msgdesq;            /* List of opened message queues           */
#endif

#ifdef CONFIG_ARCH_ADDRENV
  /* Address Environment ********************************************************/

  group_addrenv_t tg_addrenv;       /* Task group address environment           */
#endif

#ifdef CONFIG_MM_SHM
  /* Shared Memory **************************************************************/

  struct group_shm_s tg_shm;        /* Task shared memory logic                 */
#endif
};

/* struct tcb_s *****************************************************************/

/* This is the common part of the task control block (TCB).  The TCB is the heart
 * of the NuttX task-control logic.  Each task or thread is represented by a TCB
 * that includes these common definitions.
 */

struct tcb_s
{
  /* Fields used to support list management *************************************/

  FAR struct tcb_s *flink;               /* Doubly linked list                  */
  FAR struct tcb_s *blink;

  /* Task Group *****************************************************************/

  FAR struct task_group_s *group;        /* Pointer to shared task group data   */

  /* Task Management Fields *****************************************************/

  pid_t    pid;                          /* This is the ID of the thread        */
  start_t  start;                        /* Thread start function               */
  entry_t  entry;                        /* Entry Point into the thread         */
  uint8_t  sched_priority;               /* Current priority of the thread      */
  uint8_t  init_priority;                /* Initial priority of the thread      */

#ifdef CONFIG_PRIORITY_INHERITANCE
#if CONFIG_SEM_NNESTPRIO > 0
  uint8_t  npend_reprio;                 /* Number of nested reprioritizations  */
  uint8_t  pend_reprios[CONFIG_SEM_NNESTPRIO];
#endif
  uint8_t  base_priority;                /* "Normal" priority of the thread     */
#endif

  uint8_t  task_state;                   /* Current state of the thread         */
#ifdef CONFIG_SMP
  uint8_t  cpu;                          /* CPU index if running or assigned    */
  cpu_set_t affinity;                    /* Bit set of permitted CPUs           */
#endif
  uint16_t flags;                        /* Misc. general status flags          */
  int16_t  lockcount;                    /* 0=preemptible (not-locked)          */
#ifdef CONFIG_IRQCOUNT
  int16_t  irqcount;                     /* 0=Not in critical section           */
#endif
#ifdef CONFIG_CANCELLATION_POINTS
  int16_t  cpcount;                      /* Nested cancellation point count     */
#endif
  int16_t  errcode;                      /* Used to pass error information      */

#if CONFIG_RR_INTERVAL > 0 || defined(CONFIG_SCHED_SPORADIC)
  int32_t  timeslice;                    /* RR timeslice OR Sporadic budget     */
                                         /* interval remaining                  */
#endif
#ifdef CONFIG_SCHED_SPORADIC
  FAR struct sporadic_s *sporadic;       /* Sporadic scheduling parameters      */
#endif

  struct wdog_s waitdog;                 /* All timed waits use this timer      */

  /* Stack-Related Fields *******************************************************/

  size_t    adj_stack_size;              /* Stack size after adjustment         */
                                         /* for hardware, processor, etc.       */
                                         /* (for debug purposes only)           */
  FAR void *stack_alloc_ptr;             /* Pointer to allocated stack          */
                                         /* Needed to deallocate stack          */
  FAR void *adj_stack_ptr;               /* Adjusted stack_alloc_ptr for HW     */
                                         /* The initial stack pointer value     */

  /* External Module Support ****************************************************/

#ifdef CONFIG_PIC
  FAR struct dspace_s *dspace;           /* Allocated area for .bss and .data   */
#endif

  /* POSIX Semaphore Control Fields *********************************************/

  sem_t *waitsem;                        /* Semaphore ID waiting on             */

  /* POSIX Signal Control Fields ************************************************/

  sigset_t   sigprocmask;                /* Signals that are blocked            */
  sigset_t   sigwaitmask;                /* Waiting for pending signals         */
  sq_queue_t sigpendactionq;             /* List of pending signal actions      */
  sq_queue_t sigpostedq;                 /* List of posted signals              */
  siginfo_t  sigunbinfo;                 /* Signal info when task unblocked     */

  /* POSIX Named Message Queue Fields *******************************************/

#ifndef CONFIG_DISABLE_MQUEUE
  FAR struct mqueue_inode_s *msgwaitq;   /* Waiting for this message queue      */
#endif

  /* Robust mutex support *******************************************************/

#if !defined(CONFIG_DISABLE_PTHREAD) && !defined(CONFIG_PTHREAD_MUTEX_UNSAFE)
  FAR struct pthread_mutex_s *mhead;     /* List of mutexes held by thread      */
#endif

  /* Clean-up stack *************************************************************/

#ifdef CONFIG_PTHREAD_CLEANUP
  /* tos   - The index to the next available entry at the top of the stack.
   * stack - The pre-allocated clean-up stack memory.
   */

  uint8_t tos;
  struct pthread_cleanup_s stack[CONFIG_PTHREAD_CLEANUP_STACKSIZE];
#endif

  /* Pre-emption monitor support ************************************************/

#ifdef CONFIG_SCHED_CRITMONITOR
  uint32_t premp_start;                  /* Time when preemption disabled       */
  uint32_t premp_max;                    /* Max time preemption disabled        */
  uint32_t crit_start;                   /* Time critical section entered       */
  uint32_t crit_max;                     /* Max time in critical section        */
#endif

  /* State save areas ***********************************************************/

  /* The form and content of these fields are platform-specific.                */

  struct xcptcontext xcp;                /* Interrupt register save area        */

#if CONFIG_TASK_NAME_SIZE > 0
  char name[CONFIG_TASK_NAME_SIZE + 1];  /* Task name (with NUL terminator)     */
#endif
};

/* struct task_tcb_s ************************************************************/

/* This is the particular form of the task control block (TCB) structure used by
 * tasks (and kernel threads).  There are two TCB forms:  one for pthreads and
 * one for tasks.  Both share the common TCB fields (which must appear at the
 * top of the structure) plus additional fields unique to tasks and threads.
 * Having separate structures for tasks and pthreads adds some complexity, but
 * saves memory in that it prevents pthreads from being burdened with the
 * overhead required for tasks (and vice versa).
 */

struct task_tcb_s
{
  /* Common TCB fields **********************************************************/

  struct tcb_s cmn;                      /* Common TCB fields                   */

  /* Task Management Fields *****************************************************/

#ifdef CONFIG_SCHED_STARTHOOK
  starthook_t starthook;                 /* Task startup function               */
  FAR void *starthookarg;                /* The argument passed to the function */
#endif

  /* [Re-]start name + start-up parameters **************************************/

  FAR char **argv;                       /* Name+start-up parameters            */
};

/* struct pthread_tcb_s *********************************************************/

/* This is the particular form of the task control block (TCB) structure used by
 * pthreads.  There are two TCB forms:  one for pthreads and one for tasks.  Both
 * share the common TCB fields (which must appear at the top of the structure)
 * plus additional fields unique to tasks and threads.  Having separate
 * structures for tasks and pthreads adds some complexity,  but saves memory in
 * that it prevents pthreads from being burdened with the overhead required for
 * tasks (and vice versa).
 */

#ifndef CONFIG_DISABLE_PTHREAD
struct pthread_tcb_s
{
  /* Common TCB fields **********************************************************/

  struct tcb_s cmn;                      /* Common TCB fields                   */

  /* Task Management Fields *****************************************************/

  pthread_addr_t arg;                    /* Startup argument                    */
  FAR void *joininfo;                    /* Detach-able info to support join    */
};
#endif /* !CONFIG_DISABLE_PTHREAD */

/* This is the callback type used by nxsched_foreach() */

typedef CODE void (*nxsched_foreach_t)(FAR struct tcb_s *tcb, FAR void *arg);

#endif /* __ASSEMBLY__ */

/********************************************************************************
 * Public Data
 ********************************************************************************/

#ifndef __ASSEMBLY__
#undef EXTERN
#if defined(__cplusplus)
#define EXTERN extern "C"
extern "C"
{
#else
#define EXTERN extern
#endif

#ifdef CONFIG_SCHED_CRITMONITOR
/* Maximum time with pre-emption disabled or within critical section. */

#ifdef CONFIG_SMP_NCPUS
EXTERN uint32_t g_premp_max[CONFIG_SMP_NCPUS];
EXTERN uint32_t g_crit_max[CONFIG_SMP_NCPUS];
#else
EXTERN uint32_t g_premp_max[1];
EXTERN uint32_t g_crit_max[1];
#endif
#endif /* CONFIG_SCHED_CRITMONITOR */

/********************************************************************************
 * Public Function Prototypes
 ********************************************************************************/

/********************************************************************************
 * Name: nxsched_self
 *
 * Description:
 *   Return the current threads TCB.  Basically, this function just wraps the
 *   head of the ready-to-run list and manages access to the TCB from outside
 *   of the sched/ sub-directory.
 *
 ********************************************************************************/

FAR struct tcb_s *nxsched_self(void);

/********************************************************************************
 * Name: nxsched_foreach
 *
 * Description:
 *   Enumerate over each task and provide the TCB of each task to a user
 *   callback functions.
 *
 *   NOTE:  This function examines the TCB and calls each handler within a
 *   critical section.  However, that critical section is released and
 *   reacquired for each TCB.  When it is released, there may be changes in
 *   tasking.  If the caller requires absolute stability through the
 *   traversal, then the caller should establish the critical section BEFORE
 *   calling this function.
 *
 * Input Parameters:
 *   handler - The function to be called with the TCB of
 *     each task
 *
 * Returned Value:
 *   None
 *
 ********************************************************************************/

void nxsched_foreach(nxsched_foreach_t handler, FAR void *arg);

/********************************************************************************
 * Name: nxsched_get_tcb
 *
 * Description:
 *   Given a task ID, this function will return the a pointer to the
 *   corresponding TCB (or NULL if there is no such task ID).
 *
 *   NOTE:  This function holds a critical section while examining TCB data
 *   data structures but releases that critical section before returning.
 *   When it is released, the TCB may become unstable.  If the caller
 *   requires absolute stability while using the TCB, then the caller
 *   should establish the critical section BEFORE calling this function and
 *   hold that critical section as long as necessary.
 *
 ********************************************************************************/

FAR struct tcb_s *nxsched_get_tcb(pid_t pid);

/********************************************************************************
 * Name:  nxsched_releasepid
 *
 * Description:
 *   When a task is destroyed, this function must be called to make its
 *   process ID available for re-use.
 *
 ********************************************************************************/

int nxsched_release_tcb(FAR struct tcb_s *tcb, uint8_t ttype);

/* File system helpers **********************************************************/

/* These functions all extract lists from the group structure associated with the
 * currently executing task.
 */

FAR struct filelist *nxsched_get_files(void);
#if CONFIG_NFILE_STREAMS > 0
FAR struct streamlist *nxsched_get_streams(void);
#endif /* CONFIG_NFILE_STREAMS */

#ifdef CONFIG_NET
FAR struct socketlist *nxsched_get_sockets(void);
#endif

/********************************************************************************
 * Name: nxtask_init
 *
 * Description:
 *   This function initializes a Task Control Block (TCB) in preparation for
 *   starting a new thread.  It performs a subset of the functionality of
 *   task_create()
 *
 *   Unlike task_create():
 *     1. Allocate the TCB.  The pre-allocated TCB is passed in argv.
 *     2. Allocate the stack.  The pre-allocated stack is passed in argv.
 *     3. Activate the task. This must be done by calling nxtask_activate().
 *
 *   Certain fields of the pre-allocated TCB may be set to change the
 *   nature of the created task.  For example:
 *
 *     - Task type may be set in the TCB flags to create kernel thread
 *
 * Input Parameters:
 *   tcb        - Address of the new task's TCB
 *   name       - Name of the new task (not used)
 *   priority   - Priority of the new task
 *   stack      - Start of the pre-allocated stack
 *   stack_size - Size (in bytes) of the stack allocated
 *   entry      - Application start point of the new task
 *   argv       - A pointer to an array of input parameters.  The array
 *                should be terminated with a NULL argv[] value. If no
 *                parameters are required, argv may be NULL.
 *
 * Returned Value:
 *   OK on success; negative error value on failure appropriately.  (See
 *   nxtask_setup_scheduler() for possible failure conditions).  On failure,
 *   the caller is responsible for freeing the stack memory and for calling
 *   nxsched_release_tcb() to free the TCB (which could be in most any
 *   state).
 *
 ********************************************************************************/

int nxtask_init(FAR struct task_tcb_s *tcb, const char *name, int priority,
                FAR void *stack, uint32_t stack_size, main_t entry,
                FAR char * const argv[]);

/********************************************************************************
 * Name: nxtask_uninit
 *
 * Description:
 *   Undo all operations on a TCB performed by task_init() and release the
 *   TCB by calling kmm_free().  This is intended primarily to support
 *   error recovery operations after a successful call to task_init() such
 *   was when a subsequent call to task_activate fails.
 *
 *   Caution:  Freeing of the TCB itself might be an unexpected side-effect.
 *
 * Input Parameters:
 *   tcb - Address of the TCB initialized by task_init()
 *
 * Returned Value:
 *   OK on success; negative error value on failure appropriately.
 *
 ********************************************************************************/

void nxtask_uninit(FAR struct task_tcb_s *tcb);

/********************************************************************************
 * Name: nxtask_activate
 *
 * Description:
 *   This function activates tasks initialized by nxtask_setup_scheduler().
 *   Without activation, a task is ineligible for execution by the
 *   scheduler.
 *
 * Input Parameters:
 *   tcb - The TCB for the task for the task (same as the nxtask_init
 *         argument).
 *
 * Returned Value:
 *   None
 *
 ********************************************************************************/

void nxtask_activate(FAR struct tcb_s *tcb);

/********************************************************************************
 * Name: nxtask_starthook
 *
 * Description:
 *   Configure a start hook... a function that will be called on the thread
 *   of the new task before the new task's main entry point is called.
 *   The start hook is useful, for example, for setting up automatic
 *   configuration of C++ constructors.
 *
 * Input Parameters:
 *   tcb - The new, unstarted task task that needs the start hook
 *   starthook - The pointer to the start hook function
 *   arg - The argument to pass to the start hook function.
 *
 * Returned Value:
 *   None
 *
 ********************************************************************************/

#ifdef CONFIG_SCHED_STARTHOOK
void nxtask_starthook(FAR struct task_tcb_s *tcb, starthook_t starthook,
                      FAR void *arg);
#endif

/********************************************************************************
 * Name: nxtask_startup
 *
 * Description:
 *   This function is the user-space, task startup function.  It is called
 *   from up_task_start() in user-mode.
 *
 * Input Parameters:
 *   entrypt - The user-space address of the task entry point
 *   argc and argv - Standard arguments for the task entry point
 *
 * Returned Value:
 *   None.  This function does not return.
 *
 ********************************************************************************/

#ifndef CONFIG_BUILD_KERNEL
void nxtask_startup(main_t entrypt, int argc, FAR char *argv[]);
#endif

/********************************************************************************
 * Internal vfork support.  The overall sequence is:
 *
 * 1) User code calls vfork().  vfork() is provided in architecture-specific
 *    code.
 * 2) vfork()and calls nxtask_setup_vfork().
 * 3) nxtask_setup_vfork() 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 input 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 nxtask_start_vfork()
 * 6) nxtask_start_vfork() then executes the child thread.
 *
 * nxtask_abort_vfork() may be called if an error occurs between steps 3 and 6.
 *
 ********************************************************************************/

FAR struct task_tcb_s *nxtask_setup_vfork(start_t retaddr, size_t *argsize);
pid_t nxtask_start_vfork(FAR struct task_tcb_s *child);
void nxtask_abort_vfork(FAR struct task_tcb_s *child, int errcode);

/********************************************************************************
 * Name: group_exitinfo
 *
 * Description:
 *   This function may be called to when a task is loaded into memory.  It
 *   will setup the to automatically unload the module when the task exits.
 *
 * Input Parameters:
 *   pid     - The task ID of the newly loaded task
 *   bininfo - This structure allocated with kmm_malloc().  This memory
 *             persists until the task exits and will be used unloads
 *             the module from memory.
 *
 * Returned Value:
 *   This is a NuttX internal function so it follows the convention that
 *   0 (OK) is returned on success and a negated errno is returned on
 *   failure.
 *
 ********************************************************************************/

#ifdef CONFIG_BINFMT_LOADABLE
struct binary_s;  /* Forward reference */
int group_exitinfo(pid_t pid, FAR struct binary_s *bininfo);
#endif

/********************************************************************************
 * Name: nxsched_resume_scheduler
 *
 * Description:
 *   Called by architecture specific implementations that block task execution.
 *   This function prepares the scheduler for the thread that is about to be
 *   restarted.
 *
 * Input Parameters:
 *   tcb - The TCB of the thread to be restarted.
 *
 * Returned Value:
 *   None
 *
 ********************************************************************************/

#if CONFIG_RR_INTERVAL > 0 || defined(CONFIG_SCHED_RESUMESCHEDULER)
void nxsched_resume_scheduler(FAR struct tcb_s *tcb);
#else
#  define nxsched_resume_scheduler(tcb)
#endif

/********************************************************************************
 * Name: nxsched_suspend_scheduler
 *
 * Description:
 *   Called by architecture specific implementations to resume task execution.
 *   This function performs scheduler operations for the thread that is about to
 *   be suspended.
 *
 * Input Parameters:
 *   tcb - The TCB of the thread to be restarted.
 *
 * Returned Value:
 *   None
 *
 ********************************************************************************/

#ifdef CONFIG_SCHED_SUSPENDSCHEDULER
void nxsched_suspend_scheduler(FAR struct tcb_s *tcb);
#else
#  define nxsched_suspend_scheduler(tcb)
#endif

/********************************************************************************
 * Name: nxsched_get_param
 *
 * Description:
 *   This function gets the scheduling priority of the task specified by
 *   pid.  It is identical in function, differing only in its return value:
 *   This function does not modify the errno variable.
 *
 *   This is a non-standard, internal OS function and is not intended for
 *   use by application logic.  Applications should use the standard
 *   sched_getparam().
 *
 * Input Parameters:
 *   pid - the task ID of the task.  If pid is zero, the priority
 *     of the calling task is returned.
 *   param - A structure whose member sched_priority is the integer
 *     priority.  The task's priority is copied to the sched_priority
 *     element of this structure.
 *
 * Returned Value:
 *   0 (OK) if successful, otherwise a negated errno value is returned to
 *   indicate the nature of the failure..
 *
 *   This function can fail if param is null (EINVAL) or if pid does
 *   not correspond to any task (ESRCH).
 *
 ********************************************************************************/

struct sched_param;  /* Forward reference */
int nxsched_get_param (pid_t pid, FAR struct sched_param *param);

/********************************************************************************
 * Name:  nxsched_set_param
 *
 * Description:
 *   This function sets the priority of a specified task.  It is identical
 *   to the function sched_setparam(), differing only in its return value:
 *   This function does not modify the errno variable.
 *
 *   NOTE: Setting a task's priority to the same value has a similar effect
 *   to sched_yield() -- The task will be moved to  after all other tasks
 *   with the same priority.
 *
 *   This is a non-standard, internal OS function and is not intended for
 *   use by application logic.  Applications should use the standard
 *   sched_setparam().
 *
 * Input Parameters:
 *   pid - the task ID of the task to reprioritize.  If pid is zero, the
 *      priority of the calling task is changed.
 *   param - A structure whose member sched_priority is the integer priority.
 *      The range of valid priority numbers is from SCHED_PRIORITY_MIN
 *      through SCHED_PRIORITY_MAX.
 *
 * Returned Value:
 *   0 (OK) if successful, otherwise a negated errno value is returned to
 *   indicate the nature of the failure..
 *
 *   EINVAL The parameter 'param' is invalid or does not make sense for the
 *          current scheduling policy.
 *   EPERM  The calling task does not have appropriate privileges.
 *   ESRCH  The task whose ID is pid could not be found.
 *
 ********************************************************************************/

struct sched_param;  /* Forward reference */
int nxsched_set_param(pid_t pid, FAR const struct sched_param *param);

/********************************************************************************
 * Name: nxsched_get_scheduler
 *
 * Description:
 *   sched_getscheduler() returns the scheduling policy currently
 *   applied to the task identified by pid.  If pid equals zero, the
 *   policy of the calling task will be retrieved.
 *
 *   This functions is identical to the function sched_getscheduler(),
 *   differing only in its return value:  This function does not modify
 *   the errno variable.
 *
 *   This is a non-standard, internal OS function and is not intended for
 *   use by application logic.  Applications should use the standard
 *   sched_getscheduler().
 *
 * Input Parameters:
 *   pid - the task ID of the task to query.  If pid is zero, the
 *     calling task is queried.
 *
 * Returned Value:
 *    On success, sched_getscheduler() returns the policy for the task
 *    (either SCHED_FIFO or SCHED_RR).  On error,  a negated errno value
 *    returned:
 *
 *      ESRCH  The task whose ID is pid could not be found.
 *
 ********************************************************************************/

int nxsched_get_scheduler(pid_t pid);

/********************************************************************************
 * Name: nxsched_set_scheduler
 *
 * Description:
 *   nxsched_set_scheduler() sets both the scheduling policy and the priority
 *   for the task identified by pid. If pid equals zero, the scheduler of
 *   the calling task will be set.  The parameter 'param' holds the priority
 *   of the thread under the new policy.
 *
 *   nxsched_set_scheduler() is identical to the function sched_getparam(),
 *   differing only in its return value:  This function does not modify the
 *    errno variable.
 *
 *   This is a non-standard, internal OS function and is not intended for
 *   use by application logic.  Applications should use the standard
 *   sched_getparam().
 *
 * Input Parameters:
 *   pid - the task ID of the task to modify.  If pid is zero, the calling
 *      task is modified.
 *   policy - Scheduling policy requested (either SCHED_FIFO or SCHED_RR)
 *   param - A structure whose member sched_priority is the new priority.
 *      The range of valid priority numbers is from SCHED_PRIORITY_MIN
 *      through SCHED_PRIORITY_MAX.
 *
 * Returned Value:
 *   On success, nxsched_set_scheduler() returns OK (zero).  On error, a
 *   negated errno value is returned:
 *
 *   EINVAL The scheduling policy is not one of the recognized policies.
 *   ESRCH  The task whose ID is pid could not be found.
 *
 ********************************************************************************/

int nxsched_set_scheduler(pid_t pid, int policy,
                          FAR const struct sched_param *param);

/********************************************************************************
 * Name: nxsched_get_affinity
 *
 * Description:
 *   nxsched_get_affinity() writes the affinity mask of the thread whose ID
 *   is pid into the cpu_set_t pointed to by mask.  The  cpusetsize
 *   argument specifies the size (in bytes) of mask.  If pid is zero, then
 *   the mask of the calling thread is returned.
 *
 *   nxsched_get_affinity() is identical to the function sched_getaffinity(),
 *   differing only in its return value:  This function does not modify the
 *   errno variable.
 *
 *   This is a non-standard, internal OS function and is not intended for
 *   use by application logic.  Applications should use the standard
 *   sched_getparam().
 *
 * Input Parameters:
 *   pid        - The ID of thread whose affinity set will be retrieved.
 *   cpusetsize - Size of mask.  MUST be sizeofcpu_set_t().
 *   mask       - The location to return the thread's new affinity set.
 *
 * Returned Value:
 *   Zero (OK) if successful.  Otherwise, a negated errno value is returned:
 *
 *     ESRCH  The task whose ID is pid could not be found.
 *
 ********************************************************************************/

#ifdef CONFIG_SMP
int nxsched_get_affinity(pid_t pid, size_t cpusetsize, FAR cpu_set_t *mask);
#endif

/********************************************************************************
 * Name: nxsched_set_affinity
 *
 * Description:
 *   sched_setaffinity() sets the CPU affinity mask of the thread whose ID
 *   is pid to the value specified by mask.  If pid is zero, then the
 *   calling thread is used.  The argument cpusetsize is the length (i
 *   bytes) of the data pointed to by mask.  Normally this argument would
 *   be specified as sizeof(cpu_set_t).
 *
 *   If the thread specified by pid is not currently running on one of the
 *   CPUs specified in mask, then that thread is migrated to one of the
 *   CPUs specified in mask.
 *
 *   nxsched_set_affinity() is identical to the function sched_setparam(),
 *   differing only in its return value:  This function does not modify
 *   the errno variable.  This is a non-standard, internal OS function and
 *   is not intended for use by application logic.  Applications should
 *   use the standard sched_setparam().
 *
 * Input Parameters:
 *   pid        - The ID of thread whose affinity set will be modified.
 *   cpusetsize - Size of mask.  MUST be sizeofcpu_set_t().
 *   mask       - The location to return the thread's new affinity set.
 *
 * Returned Value:
 *   Zero (OK) if successful.  Otherwise, a negated errno value is returned:
 *
 *     ESRCH  The task whose ID is pid could not be found.
 *
 ********************************************************************************/

#ifdef CONFIG_SMP
int nxsched_set_affinity(pid_t pid, size_t cpusetsize,
                         FAR const cpu_set_t *mask);
#endif

/********************************************************************************
 * Name: nxsched_get_stackinfo
 *
 * Description:
 *   Report information about a thread's stack allocation.
 *
 * Input Parameters:
 *   pid       - Identifies the thread to query.  Zero is interpreted as the
 *               the calling thread
 *   stackinfo - User-provided location to return the stack information.
 *
 * Returned Value:
 *   Zero (OK) if successful.  Otherwise, a negated errno value is returned.
 *
 *     -ENOENT  Returned if pid does not refer to an active task
 *     -EACCES  The calling thread does not have privileges to access the
 *              stack of the thread associated with the pid.
 *
 ********************************************************************************/

int nxsched_get_stackinfo(pid_t pid, FAR struct stackinfo_s *stackinfo);

/********************************************************************************
 * Name: nx_wait/nx_waitid/nx_waitpid
 ********************************************************************************/

#ifdef CONFIG_SCHED_WAITPID
pid_t nx_wait(FAR int *stat_loc);
int   nx_waitid(int idtype, id_t id, FAR siginfo_t *info, int options);
pid_t nx_waitpid(pid_t pid, FAR int *stat_loc, int options);
#endif

#undef EXTERN
#if defined(__cplusplus)
}
#endif
#endif /* __ASSEMBLY__ */

#endif /* __INCLUDE_NUTTX_SCHED_H */