thread.h

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

/*  thread.h
 *
 *  This include file contains all constants and structures associated
 *  with the thread control block.
 *
 *  COPYRIGHT (c) 1989-1999.
 *  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 1.47.2.2 2003/09/15 02:12:47 ralf Exp $
 */

#ifndef __THREAD_h
#define __THREAD_h

#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 unsigned32. :)
 */

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 unsigned32 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;

typedef Thread ( *Thread_Entry )();   /* basic type */

typedef Thread ( *Thread_Entry_numeric )( unsigned32 );
typedef Thread ( *Thread_Entry_pointer )( void * );
typedef Thread ( *Thread_Entry_both_pointer_first )( void *, unsigned32 );
typedef Thread ( *Thread_Entry_both_numeric_first )( unsigned32, 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;

typedef struct Thread_Control_struct Thread_Control;

typedef void (*Thread_CPU_budget_algorithm_callout )( Thread_Control * );

/*
 *  Per task variable structure
 */

struct rtems_task_variable_tt;

struct rtems_task_variable_tt {
  struct rtems_task_variable_tt  *next;
  void                          **ptr;
  void                           *gval;
  void                           *tval;
  void                          (*dtor)(void *);
};

typedef struct rtems_task_variable_tt   rtems_task_variable_t;

/*
 *  The following structure contains the information which defines
 *  the starting state of a thread.
 */

typedef struct {
  Thread_Entry         entry_point;      /* starting thread address         */
  Thread_Start_types   prototype;        /* how task is invoked             */
  void                *pointer_argument; /* pointer argument                */
  unsigned32           numeric_argument; /* numeric argument                */
                                         /* initial execution modes         */
  boolean              is_preemptible;
  Thread_CPU_budget_algorithms          budget_algorithm;
  Thread_CPU_budget_algorithm_callout   budget_callout;
  unsigned32           isr_level;
  Priority_Control     initial_priority; /* initial priority                */
  boolean              core_allocated_stack;
  Stack_Control        Initial_stack;    /* stack information               */
#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
  void                *fp_context;       /* initial FP context area address */
#endif
  void                *stack;            /* initial stack area address      */
}   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

typedef struct {
  Objects_Id            id;              /* waiting on this object       */
  unsigned32            count;           /* "generic" fields to be used */
  void                 *return_argument; /*   when blocking */
  void                 *return_argument_1;
  unsigned32            option;

  /*
   *  NOTE: The following assumes that all API return codes can be
   *        treated as an unsigned32.  
   */
  unsigned32            return_code;     /* status for thread awakened   */

  Chain_Control         Block2n;         /* 2 - n priority blocked chain */
  Thread_queue_Control *queue;           /* pointer to thread 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 {
  Objects_Control          Object;
  States_Control           current_state;
  Priority_Control         current_priority;
  Priority_Control         real_priority;
  unsigned32               resource_count;
  Thread_Wait_information  Wait;
  Watchdog_Control         Timer;
#if defined(RTEMS_MULTIPROCESSING)
  MP_packet_Prefix        *receive_packet;
#endif
     /****************** end of common block ********************/
  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 {
  THREAD_API_RTEMS,
  THREAD_API_POSIX,
  THREAD_API_ITRON
}  Thread_APIs;

#define THREAD_API_FIRST THREAD_API_RTEMS
#define THREAD_API_LAST  THREAD_API_ITRON

struct Thread_Control_struct {
  Objects_Control                       Object;
  States_Control                        current_state;
  Priority_Control                      current_priority;
  Priority_Control                      real_priority;
  unsigned32                            resource_count;
  Thread_Wait_information               Wait;
  Watchdog_Control                      Timer;
#if defined(RTEMS_MULTIPROCESSING)
  MP_packet_Prefix                     *receive_packet;
#endif
     /****************** end of common block ********************/
  unsigned32                            suspend_count;
  boolean                               is_global;
  boolean                               do_post_task_switch_extension;

  boolean                               is_preemptible;
  void                                 *rtems_ada_self;
  unsigned32                            cpu_time_budget;
  Thread_CPU_budget_algorithms          budget_algorithm;
  Thread_CPU_budget_algorithm_callout   budget_callout;

  unsigned32                            ticks_executed;
  Chain_Control                        *ready;
  Priority_Information                  Priority_map;
  Thread_Start_information              Start;
  Context_Control                       Registers;
#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
  void                                 *fp_context;
#endif
  struct _reent                        *libc_reent;
  void                                 *API_Extensions[ THREAD_API_LAST + 1 ];
  void                                **extensions;
  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;
 
/*
 *  The following declares the dispatch critical section nesting
 *  counter which is used to prevent context switches at inopportune
 *  moments.
 */

SCORE_EXTERN volatile unsigned32 _Thread_Dispatch_disable_level;

/*
 *  If this is non-zero, then the post-task switch extension
 *  is run regardless of the state of the per thread flag.
 */

SCORE_EXTERN unsigned32 _Thread_Do_post_task_switch_extension;

/*
 *  The following holds how many user extensions are in the system.  This
 *  is used to determine how many user extension data areas to allocate
 *  per thread.
 */

SCORE_EXTERN unsigned32 _Thread_Maximum_extensions;

/*
 *  The following is used to manage the length of a timeslice quantum.
 */

SCORE_EXTERN unsigned32 _Thread_Ticks_per_timeslice;

/*
 *  The following points to the array of FIFOs used to manage the
 *  set of ready threads.
 */

SCORE_EXTERN Chain_Control *_Thread_Ready_chain;

/*
 *  The following points to the thread which is currently executing.
 *  This thread is implicitly manipulated by numerous directives.
 */

SCORE_EXTERN Thread_Control *_Thread_Executing;

/*
 *  The following points to the highest priority ready thread
 *  in the system.  Unless the current thread is not preemptibl,
 *  then this thread will be context switched to when the next
 *  dispatch occurs.
 */

SCORE_EXTERN Thread_Control *_Thread_Heir;

/*
 *  The following points to the thread whose floating point
 *  context is currently loaded.
 */

#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
SCORE_EXTERN Thread_Control *_Thread_Allocated_fp;
#endif

/*
 * The C library re-enter-rant global pointer. Some C library implementations
 * such as newlib have a single global pointer that changed during a context
 * switch. The pointer points to that global pointer. The Thread control block
 * holds a pointer to the task specific data.
 */
SCORE_EXTERN struct _reent **_Thread_libc_reent;

/*
 *  _Thread_Handler_initialization
 *
 *  DESCRIPTION:
 *
 *  This routine performs the initialization necessary for this handler.
 */

void _Thread_Handler_initialization (
  unsigned32   ticks_per_timeslice,
  unsigned32   maximum_extensions,
  unsigned32   maximum_proxies
);

/*
 *  _Thread_Create_idle
 *
 *  DESCRIPTION:
 *
 *  This routine creates the idle thread.
 *
 *  WARNING!! No thread should be created before this one.
 */
 
void _Thread_Create_idle( void );

/*
 *  _Thread_Start_multitasking
 *
 *  DESCRIPTION:
 *
 *  This routine initiates multitasking.  It is invoked only as
 *  part of initialization and its invocation is the last act of
 *  the non-multitasking part of the system initialization.
 */

void _Thread_Start_multitasking( void );

/*
 *  _Thread_Dispatch
 *
 *  DESCRIPTION:
 *
 *  This routine is responsible for transferring control of the
 *  processor from the executing thread to the heir thread.  As part
 *  of this process, it is responsible for the following actions:
 *
 *     + saving the context of the executing thread
 *     + restoring the context of the heir thread
 *     + dispatching any signals for the resulting executing thread
 */

void _Thread_Dispatch( void );

/*
 *  _Thread_Stack_Allocate
 *  
 *  DESCRIPTION:
 *
 *  Allocate the requested stack space for the thread.
 *  return the actual size allocated after any adjustment
 *  or return zero if the allocation failed.