thread.h

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/** 
 *  @file  rtems/score/thread.h
 *
 *  This include file contains all constants and structures associated
 *  with the thread control block.
 */

/*
 *  COPYRIGHT (c) 1989-2006.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 *  $Id: thread.h,v 1.58 2006/01/16 15:13:58 joel Exp $
 */

#ifndef _RTEMS_SCORE_THREAD_H
#define _RTEMS_SCORE_THREAD_H

/**
 *  @defgroup ScoreThread Thread Handler
 *
 *  This handler encapsulates functionality related to the management of
 *  threads.  This includes the creation, deletion, and scheduling of threads.
 */
/**@{*/

#ifdef __cplusplus
extern "C" {
#endif

#include <rtems/score/context.h>
#include <rtems/score/cpu.h>
#if defined(RTEMS_MULTIPROCESSING)
#include <rtems/score/mppkt.h>
#endif
#include <rtems/score/object.h>
#include <rtems/score/priority.h>
#include <rtems/score/stack.h>
#include <rtems/score/states.h>
#include <rtems/score/tod.h>
#include <rtems/score/tqdata.h>
#include <rtems/score/watchdog.h>

/**
 *  The following defines the "return type" of a thread.
 *
 *  @note  This cannot always be right.  Some APIs have void
 *         tasks/threads, others return pointers, others may
 *         return a numeric value.  Hopefully a pointer is
 *         always at least as big as an uint32_t  . :)
 */
typedef void *Thread;

/**
 *  The following defines the ways in which the entry point for a
 *  thread can be invoked.  Basically, it can be passed any
 *  combination/permutation of a pointer and an uint32_t   value.
 *
 *  @note For now, we are ignoring the return type.
 */
typedef enum {
  THREAD_START_NUMERIC,
  THREAD_START_POINTER,
  THREAD_START_BOTH_POINTER_FIRST,
  THREAD_START_BOTH_NUMERIC_FIRST
} Thread_Start_types;

/** This type corresponds to a very simple style thread entry point. */
typedef Thread ( *Thread_Entry )();   /* basic type */

/** This type corresponds to a thread entry point which takes a single
 *  unsigned thirty-two bit integer as an argument.
 */
typedef Thread ( *Thread_Entry_numeric )( uint32_t   );

/** This type corresponds to a thread entry point which takes a single
 *  untyped pointer as an argument.
 */
typedef Thread ( *Thread_Entry_pointer )( void * );

/** This type corresponds to a thread entry point which takes a single
 *  untyped pointer and an unsigned thirty-two bit integer as arguments.
 */
typedef Thread ( *Thread_Entry_both_pointer_first )( void *, uint32_t   );

/** This type corresponds to a thread entry point which takes a single
 *  unsigned thirty-two bit integer and an untyped pointer and an
 *  as arguments.
 */
typedef Thread ( *Thread_Entry_both_numeric_first )( uint32_t  , void * );

/**
 *  The following lists the algorithms used to manage the thread cpu budget.
 *
 *  Reset Timeslice:   At each context switch, reset the time quantum.
 *  Exhaust Timeslice: Only reset the quantum once it is consumed.
 *  Callout:           Execute routine when budget is consumed.
 */
typedef enum {
  THREAD_CPU_BUDGET_ALGORITHM_NONE,
  THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE,
  THREAD_CPU_BUDGET_ALGORITHM_EXHAUST_TIMESLICE,
  THREAD_CPU_BUDGET_ALGORITHM_CALLOUT
}  Thread_CPU_budget_algorithms;

/** This type defines the Thread Control Block structure.
 */
typedef struct Thread_Control_struct Thread_Control;

/**  This defines thes the entry point for the thread specific timeslice
 *   budget management algorithm.
 */
typedef void (*Thread_CPU_budget_algorithm_callout )( Thread_Control * );

/** @brief Per Task Variable Manager Structure Forward Reference
 *
 *  Forward reference to the per task variable structure.
 */
struct rtems_task_variable_tt;

/** @brief Per Task Variable Manager Structure
 *
 *  This is the internal structure used to manager per Task Variables.
 */
typedef struct {
  /** This field points to the next per task variable for this task. */
  struct rtems_task_variable_tt  *next;
  /** This field points to the physical memory location of this per
   *  task variable.
   */
  void                          **ptr;
  /** This field is to the global value for this per task variable. */
  void                           *gval;
  /** This field is to this thread's value for this per task variable. */
  void                           *tval;
  /** This field points to the destructor for this per task variable. */
  void                          (*dtor)(void *);
} rtems_task_variable_t;

/**
 *  The following structure contains the information which defines
 *  the starting state of a thread.
 */
typedef struct {
  /** This field is the starting address for the thread. */
  Thread_Entry         entry_point;
  /** This field indicatres the how task is invoked. */
  Thread_Start_types   prototype;
  /** This field is the pointer argument passed at thread start. */
  void                *pointer_argument;
  /** This field is the numeric argument passed at thread start. */
  uint32_t             numeric_argument;
  /*-------------- initial execution modes ----------------- */
  /** This field indicates whether the thread was preemptible when
    * it started.
    */
  boolean              is_preemptible;
  /** This field indicates the CPU budget algorith. */
  Thread_CPU_budget_algorithms          budget_algorithm;
  /** This field is the routine to invoke when the CPU allotment is
   *  consumed.
   */
  Thread_CPU_budget_algorithm_callout   budget_callout;
  /** This field is the initial ISR disable level of this thread. */
  uint32_t             isr_level;
  /** This field is the initial priority. */
  Priority_Control     initial_priority;
  /** This field indicates whether the SuperCore allocated the stack. */
  boolean              core_allocated_stack;
  /** This field is the stack information. */
  Stack_Control        Initial_stack;
#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
  /** This field is the initial FP context area address. */
  void                *fp_context;
#endif
  /** This field is the initial stack area address. */
  void                *stack;
}   Thread_Start_information;

/**
 *  The following structure contains the information necessary to manage
 *  a thread which it is  waiting for a resource.
 */
#define THREAD_STATUS_PROXY_BLOCKING 0x1111111

/** @brief Thread Blocking Management Information
 *
 *  This contains the information required to manage a thread while it is
 *  blocked and to return information to it.
 */
typedef struct {
  /** This field is the Id of the object this thread is waiting upon. */
  Objects_Id            id;
  /** This field is used to return an integer while when blocked. */
  uint32_t              count;
  /** This field is the first pointer to a user return argument. */
  void                 *return_argument;
  /** This field is the second pointer to a user return argument. */
  void                 *return_argument_1;
  /** This field contains any options in effect on this blocking operation. */
  uint32_t              option;
  /** This field will contain the return status from a blocking operation.
   * 
   *  @note The following assumes that all API return codes can be
   *        treated as an uint32_t.
   */
  uint32_t              return_code;

  /** This field is the chain header for the second through Nth tasks 
   *  of the same priority blocked waiting on the same object.
   */
  Chain_Control         Block2n;
  /** This field points to the thread queue on which this thread is blocked. */
  Thread_queue_Control *queue;
}   Thread_Wait_information;

/**
 *  The following defines the control block used to manage
 *  each thread proxy.
 *
 *  @note It is critical that proxies and threads have identical
 *        memory images for the shared part.
 */
typedef struct {
  /** This field is the object management structure for each proxy. */
  Objects_Control          Object;
  /** This field is the current execution state of this proxy. */
  States_Control           current_state;
  /** This field is the current priority state of this proxy. */
  Priority_Control         current_priority;
  /** This field is the base priority of this proxy. */
  Priority_Control         real_priority;
  /** This field is the number of mutexes currently held by this proxy. */
  uint32_t                 resource_count;
  /** This field is the blocking information for this proxy. */
  Thread_Wait_information  Wait;
  /** This field is the Watchdog used to manage proxy delays and timeouts. */
  Watchdog_Control         Timer;
#if defined(RTEMS_MULTIPROCESSING)
  /** This field is the received response packet in an MP system. */
  MP_packet_Prefix        *receive_packet;
#endif
     /****************** end of common block ********************/
  /** This field is used to manage the set of proxies in the system. */
  Chain_Node               Active;
}   Thread_Proxy_control;

/**
 *  The following record defines the control block used
 *  to manage each thread.
 *
 *  @note It is critical that proxies and threads have identical
 *        memory images for the shared part.
 */
typedef enum {
  /** This value is for the Classic RTEMS API. */
  THREAD_API_RTEMS,
  /** This value is for the POSIX API. */
  THREAD_API_POSIX,
  /** This value is for the ITRON API. */
  THREAD_API_ITRON
}  Thread_APIs;

/** This macro defines the first API which has threads. */
#define THREAD_API_FIRST THREAD_API_RTEMS

/** This macro defines the last API which has threads. */
#define THREAD_API_LAST  THREAD_API_ITRON

/**
 *  This structure defines the Thread Control Block (TCB).
 */
struct Thread_Control_struct {
  /** This field is the object management structure for each thread. */
  Objects_Control          Object;
  /** This field is the current execution state of this thread. */
  States_Control           current_state;
  /** This field is the current priority state of this thread. */
  Priority_Control         current_priority;
  /** This field is the base priority of this thread. */
  Priority_Control         real_priority;
  /** This field is the number of mutexes currently held by this thread. */
  uint32_t                 resource_count;
  /** This field is the blocking information for this thread. */
  Thread_Wait_information  Wait;
  /** This field is the Watchdog used to manage thread delays and timeouts. */
  Watchdog_Control         Timer;
#if defined(RTEMS_MULTIPROCESSING)
  /** This field is the received response packet in an MP system. */
  MP_packet_Prefix        *receive_packet;
#endif
     /*================= end of common block =================*/
  /** This field is the number of nested suspend calls. */
  uint32_t                              suspend_count;
  /** This field is true if the thread is offered globally */
  boolean                               is_global;
  /** This field is is true if the post task context switch should be 
   *  executed for this thread at the next context switch.
   */
  boolean                               do_post_task_switch_extension;
  /** This field is true if the thread is preemptible. */
  boolean                               is_preemptible;
  /** This field is the GNAT self context pointer. */
  void                                 *rtems_ada_self;
  /** This field is the length of the time quantum that this thread is
   *  allowed to consume.  The algorithm used to manage limits on CPU usage
   *  is specified by budget_algorithm.
   */
  uint32_t                              cpu_time_budget;
  /** This field is the algorithm used to manage this thread's time
   *  quantum.  The algorithm may be specified as none which case,
   *  no limit is in place.
   */
  Thread_CPU_budget_algorithms          budget_algorithm;
  /** This field is the method invoked with the budgeted time is consumed. */
  Thread_CPU_budget_algorithm_callout   budget_callout;

  /** This field is the number of clock ticks executed by this thread
   *  since it was created.
   */
  uint32_t                              ticks_executed;
  /** This field points to the Ready FIFO for this priority. */
  Chain_Control                        *ready;
  /** This field contains precalculated priority map indices. */
  Priority_Information                  Priority_map;
  /** This field contains information about the starting state of
   *  this thread.
   */
  Thread_Start_information              Start;
  /** This field contains the context of this thread. */
  Context_Control                       Registers;
#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
  /** This field points to the floating point context for this thread.
   *  If NULL, the thread is integer only.
   */
  void                                 *fp_context;
#endif
  /** This field points to the newlib reentrancy structure for this thread. */
  struct _reent                        *libc_reent;
  /** This array contains the API extension area pointers. */
  void                                 *API_Extensions[ THREAD_API_LAST + 1 ];
  /** This field points to the user extension pointers. */
  void                                **extensions;
  /** This field points to the set of per task variables. */
  rtems_task_variable_t                *task_variables;
};

/**
 *  Self for the GNU Ada Run-Time
 */
SCORE_EXTERN void *rtems_ada_self;

/**
 *  The following defines the information control block used to
 *  manage this class of objects.
 */
SCORE_EXTERN Objects_Information _Thread_Internal_information;

/**
 *  The following define the thread control pointers used to access
 *  and manipulate the idle thread.
 */
SCORE_EXTERN Thread_Control *_Thread_Idle;

/**
 *  The following context area contains the context of the "thread"
 *  which invoked the start multitasking routine.  This context is
 *  restored as the last action of the stop multitasking routine.  Thus
 *  control of the processor can be returned to the environment
 *  which initiated the system.
 */
SCORE_EXTERN Context_Control _Thread_BSP_context;