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//fsf_core.h

//=================================================================

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//

// Basic FSF(FIRST Scheduling Framework) contract management

//================================================================

/**

   \defgroup core Core module

   This module includes the basic functions and services that are

   provided by any FSF implementation. This module includes basic type

   definitions, and functions to

   - create a contract and initialize it

   - set/get the basci parameters of a contract

   - negotiate a service contract, obtaining a server id

   - create and bind threads to servers

   - create/destroy a synchronization object

   - manage bounded workloads

*/

/*@{*/

/**

   \file fsf_core.h

   This file contains the types, definitions and function prototypes

   for the core module of the First Scheduling Framework.

 */

#include <time.h>

#include <pthread.h>

#include <sys/types.h>

#include "stdbool.h"

#include "fsf_configuration_parameters.h"

#include "fsf_opaque_types.h"

#include "fsf_basic_types.h"

#ifndef _FSF_CORE_H_

#define _FSF_CORE_H_

/////////////////////////////////////////////////////////////////

//      BASIC TYPES AND CONSTANTS are in fsf_basic_types.h

/////////////////////////////////////////////////////////////////

/**

   This function converts an error code to an error message that is

   stored in the buffer starting at the location pointed to by

   message. The size of this buffer is specified by the size

   argument. If the error message is longer than size-1, it is

   truncated to that length. Regardless of whether the message is

   truncated or not, a final zero character that marks the end of the

   string is stored in the buffer.  The function fails if the error

   code passed does not correspond to any of the fsf error codes.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  error is not a valid value

    ]

*/

int fsf_strerror (int error, char *message, size_t size);

/////////////////////////////////////////////////////////////

//                       CONTRACT PARAMETERS

/////////////////////////////////////////////////////////////

/**

   \defgroup contract Contract Creation and Initialization.

   These functions are used to create and initialize a contract, and

   set its parameters.

 */

/*@{*/

/**

    Contract parameters type; it is an opaque type (i.e. the internal

    structure of this data type is implementation dependent). The user

    can access and modify the parameters of a contract only with the

    proper functions, and should never access the data directly.

*/

typedef FSF_CONTRACT_PARAMETERS_T_OPAQUE fsf_contract_parameters_t;

/**

    The operation receives a pointer to a contract parameters object

    and initializes it, setting it to the default values.

    The default values are:

    - budget min and max are set to 0

    - period min and max are set to 0

    - the workload is unbounded (FSF_INDETERMINATE)

    - the server deadline is equal to the period

    - the budget and deadline overrun are not notified

    - the granularity is set to "continuous"

    - the quality and importance are set to the default values

      (PEPPE: implementation dependent??)

    - the scheduling policy is FSF_NONE

    @param     contract the pointer to the contract variable.

    @returns  (PEPPE: should not return anything! change to void??)

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  contract is NULL

    ]

*/

int fsf_initialize_contract (fsf_contract_parameters_t *contract);

//  budget_min                => {0,0};

//  period_max                => {0,0};

//  budget_max                => {0,0};

//  period_min                => {0,0};

//  workload                  => DEFAULT_WORKLOAD;

//  d_equals_t                => DEFAULT_D_EQUALS_T; (false or true)

//  deadline                  => DEFAULT_DEADLINE;

//  budget_overrun_sig_notify => 0;  (signal number)

//  budget_overrun_sig_value  => {0, NULL};

//  deadline_miss_sig_notify  => 0;  (signal number)

//  deadline_miss_sig_value   => {0, NULL};

//

//  granularity               => DEFAULT_GRANULARITY;

//  utilization_set;          => size = 0

//  quality                   => DEFAULT_QUALITY;    (range 0..100)

//  importance                => DEFAULT_IMPORTANCE; (range 1..5)

//

//  preemption_level          => 0; (range 1..2**32-1)

//  critical_sections;        => size = 0

//  sched_policy              => DEFAULT_SCHED_POLICY

//                              (FSF_NONE)

/**

   The operation updates the specified contract parameters object by

   setting its budget, period, and workload to the specified input

   parameters. (Note: the workload is a basic parameter because

   bounded tasks are triggered by the scheduler (see the

   fsf_schedule_timed_job() operation), while indeterminate tasks are

   not; therefore, their programming model is quite different).

   @param contract     the pointer to the contract object

   @param [in] budget_min   the minimum budget for the contract

   @param [in] period_max   the maximum period for the contract

   @param [in] workload     the kind of workload (can be FSF_BOUNDED,

   FSF_INDETERMINATE or FSF_OVERHEAD)

   @returns 0 if the operation is succesful

   @returns FSF_ERR_BAD_ARGUMENT if some of the arguments is not in

            the expected range

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if any of the pointers is NULL

       or if only one of the timespec values is 0, and also if the workload

       is not a proper value (FSF_INDETERMINATE, FSF_BOUNDED, or FSF_OVERHEAD)

    ]

*/

int

fsf_set_contract_basic_parameters

  (fsf_contract_parameters_t *contract,

   const struct timespec     *budget_min,

   const struct timespec     *period_max,

   fsf_workload_t            workload);

/**

   This operation obtains from the specified contract parameters

   object its budget, period, and workload, and copies them to the

   places pointed to by the corresponding input parameters.

   @param [in] contract   the pointer to the contract object

   @param[out] budget_min pointer to the variable that will contain

   the minimum budget

   @param[out] period_max pointer to the variable that will contain the

   max_period

   @param[out] workload pointer to the variable that will contain the

   workload type

   @returns (PEPPE: this should return nothing!)

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if contract is NULL

    ]

*/

int

fsf_get_contract_basic_parameters

  (const fsf_contract_parameters_t *contract,

   struct timespec  *budget_min,

   struct timespec  *period_max,

   fsf_workload_t   *workload);

/**

   The operation updates the specified contract parameters

   object, specifying the additional parameters requirements of

   a contract.

   @param  contract The pointer to the contract object

   @param [in] d_equals_t It is a boolean value, set to true (1) if the

                 we want to specify a deadline different from the period

                 for the contract.

   @param [in] deadline If the previous parameter is set to true,

                 this parameter should be set to NULL_DEADLINE. Otherwise,

                 it contains the desired deadline value.

                 (PEPPE: should be return with error otherwise?)

   @param [in] budget_overrun_sig_notify contains the number of posix signal

                 that must be raised if the budget of the server is overrun.

                 If the value of this parameter is NULL_SIGNAL, no signal will

                 be raised.

   @param [in] budget_overrun_sig_value contains the value that will be

                 passed to the signal "catcher" when the signal is raised.

                 This parameters is not used if the budget_overrun_sig_notify

                 parameters is set to NULL_SIGNAL.

   @param [in] deadline_miss_sig_notify contains the number of posix

                 signal that must be raised if the deadline of the server

                 is missed. If the value of this parameter is NULL_SIGNAL,

                 no signal is raised.

   @param [in] deadline_miss_sig_value contains the value that will be

                 passed to the signal "catcher" when the signal is raised.

                 This parameters is not used if the budget_overrun_sig_notify

                 parameters is set to NULL_SIGNAL

   @returns 0    if the operation is succesful

   @returns FSF_BAD_ARGUMENT if some argument is out of range or not

                 admissible.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if contract is NULL or  

       (d_equals_t is true and  deadline is not FSF_NULL_DEADLINE) or

       (budget_overrun_sig_notify is not a valid signal)  or

       (deadline_miss_sig_notify is not a valid signal)  or

       (d_equals_t is false but (deadline is FSF_NULL_DEADLINE or its value

                                 is grater than the contract´s maximum period)))

    ]

   @see sigexplanation

*/

int

fsf_set_contract_timing_requirements

  (fsf_contract_parameters_t *contract,

   bool                   d_equals_t,

   const struct timespec *deadline,

   int                    budget_overrun_sig_notify,

   union sigval           budget_overrun_sig_value,

   int                    deadline_miss_sig_notify,

   union sigval           deadline_miss_sig_value);

/**

   The operation obtains the corresponding input parameters from the

   specified contract parameters object. If d_equals_t is true, the

   deadline will not be updated.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if contract is NULL

    ]

*/

int

fsf_get_contract_timing_requirements

  (const fsf_contract_parameters_t *contract,

   bool                    *d_equals_t,

   struct timespec         *deadline,

   int                     *budget_overrun_sig_notify,

   union sigval            *budget_overrun_sig_value,

   int                     *deadline_miss_sig_notify,

   union sigval            *deadline_miss_sig_value);

/*@}*/

//////////////////////////////////////////////////////////////////

//                 SYNCHRONIZATION OBJECTS

//////////////////////////////////////////////////////////////////

/**

   \defgroup synch  Synchronization objects

*/

/*@{*/

/**

   An abstract synchronization object is defined by the application.

   This object can be used by an application to wait for an event to

   arrive by invoking the fsf_schedule_triggered_job() operation.  It

   can also be used to signal the event either causing a waiting

   server to wake up, or the event to be queued if no server is

   waiting for it.

*/

typedef FSF_SYNCH_OBJ_HANDLE_T_OPAQUE fsf_synch_obj_handle_t;

/**

   This operation creates and initializes a synchronization object

   variable managed by the scheduler, and returns a handle to it in

   the variable pointed to by synch_handle.

   @param[out]  pointer to the variable that will contain the handle to the

                newly created synchronization object

   @returns     0 if the operation is succesful

   @returns     FSF_ERR_TOO_MANY_SYNCH_OBJS if the number of synchronization

                objects in the system has already exceeded the maximum

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if synch_handle is 0

     FSF_ERR_TOO_MANY_SYNCH_OBJS : if the number of synchronization

       objects in the system has already exceeded the maximum

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

    ]

*/

int

fsf_create_synch_obj

    (fsf_synch_obj_handle_t *synch_handle);

/**

   This function sends a notification to the synchronization object

   specified as parameter. If there is at least one thread waiting on

   the synchronization object, it is awaken. If more than one thread

   is waiting, just one of them is awaken. However, which one is

   awaken is implementation dependent. If no thread is waiting on the

   synchronization object, the notification is queued.

    [JULIO: all the ocurrrences of the word "thread" should be changed

       by "server" in the paragraph above

    ]

   @param [in] synch_handle the handle of the synchronization object to

                  notify.

   @returns 0 if the operation is completed succesfully

   @returns FSF_ERR_INVALID_SYNCH_OBJ_HANDLE is the handle is not valid

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if synch_handle is 0

     FSF_ERR_INVALID_SYNCH_OBJ_HANDLE if the handle is not valid

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_TOO_MANY_EVENTS_IN_SYNCH_OBJ : if the number of events stored

       in the synchronization object reaches the maximum defined in the

       configuration parameter header file

    ]

   @sa fsf_schedule_triggered_job, fsf_timed_schedule_triggered_job

*/

int

fsf_signal_synch_obj

    (fsf_synch_obj_handle_t synch_handle);

/**

   This operation destroys the synchronization object (created by a

   previous call to fsf_create_synch_obj) that is referenced by the

   synch_handle variable. After calling this operation, the

   synch_handle variable can not be used until it is initialized again

   by a call to fsf_create_synch_obj.

   @param synch_handle the handle to the synchronization object

             to be destroyed

   @returns 0 if the operation is succesful

   @returns FSF_ERR_INVALID_SYNCH_OBJ_HANDLE is the handle is not valid

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if synch_handle is 0

     FSF_ERR_INVALID_SYNCH_OBJ_HANDLE if the handle is not valid

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

    ]

   @sa fsf_create_synch_obj

*/

int

fsf_destroy_synch_obj

    (fsf_synch_obj_handle_t synch_handle);

// In the future we may add a broadcast operation that would signal a

// group of synchronization objects. We have not included a broadcast

// service in this version because it can be easily created by the

// user by signalling individual synchronization objects inside a

// loop.

// Notice that for synchronization objects there is no naming service

// like in shared objects because tasks that use synchronization are

// not developed independently, as they are closely coupled.

////////////////////////////////////////////////////

//           SCHEDULING BOUNDED WORKLOADS

////////////////////////////////////////////////////

/**

   This operation is invoked by threads associated with bounded

   workload servers to indicate that a job has been completed (and

   that the scheduler may reassign the unused capacity of the current

   job to other servers). It is also invoked when the first job of

   such threads has to be scheduled.  (PEPPE: I have a question, what

   happens to the budget? if I do not get it wrong, the replenishment

   time is set to abs_time and the bandwidth of the server up to time

   abs_time can be reassigned. Is it true? what is the exact

   relationship between this abs_time and the server period? What if

   the user specifies an abs_time less than the end of the current

   server period??)

   As an effect, the system will make the current server's budget zero

   for the remainder of the server's period, and will not replenish

   the budget until the specified absolute time.  At that time, all

   pending budget replenishments (if any) are made effective. Once the

   server has a positive budget and the scheduler schedules the

   calling thread again, the call returns and at that time, except for

   those parameters equal to NULL pointers, the system reports the

   current period and budget for the current job, whether the deadline

   of the previous job was missed or not, and whether the budget of

   the previous job was overrun or not.

   In a system with hierarchical scheduling, since this call makes the

   budget zero, the other threads in the same server are not run. As

   mentioned abobe, only when the call finishes the budget may be

   replenished.

   @param [in] abs_time     absolute time at which the budget will be

                            replenished

   @param [out] next_budget upon return of this function, the variable

                            pointed by this function will be equal to

                            the current server budget. If this parameter is

                            set to NULL, no action is taken.

   @param [out] next_period upon return of this function, the variable

                            pointed by this function will be equal to

                            the current server period. If this parameter is

                            set to NULL, no action is taken.

   @param [out] was_deadline_missed upon return of this function, the

                            variable pointed by this function will be

                            equal to true if the previous server deadline

                            was missed, to false otherwise. If this

                            parameter is set to NULL, no action is

                            taken.

   @param [out] was_budget_overrun upon return of this function, the

                            variable pointed by this function will be

                            equal to true if the previous server budget was

                            overrun, to false otherwise. If this

                            parameter is set to NULL, no action is

                            taken.

   @returns 0 if the operation is succesful

   @returns FSF_ERR_TIME_SPEC_IN_THE_PAST if the absolute time specification

              is in the past.

    [ERR@RETURNED:

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_INTERNAL_ERROR : erroneous binding or malfunction of the FSF

       main scheduler

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not scheduled

       under the FSF

     FSF_ERR_NOT_BOUND_THREAD : if the calling thread does not have a valid

       server bound to it

     FSF_ERR_BAD_ARGUMENT :  if abs_time is NULL

     FSF_ERR_SERVER_WORKLOAD_NOT_COMPATIBLE: if the kind of workload of the server

       is not FSF_BOUNDED

    ]

   @sa fsf_schedule_triggered_job, fsf_timed_schedule_triggered_job

*/

int

fsf_schedule_timed_job

  (const struct timespec *abs_time,

   struct timespec       *next_budget,

   struct timespec       *next_period,

   bool                  *was_deadline_missed,

   bool                  *was_budget_overran);

/**

   This operation is invoked by threads associated with bounded

   workload servers to indicate that a job has been completed (and

   that the scheduler may reassign the unused capacity of the current

   job to other servers). It is also invoked when the first job of

   such threads has to be scheduled. If the specified synchronization

   object has events queued, one of them is dequeued; otherwise the

   server will wait upon the specified synchronization object, the

   server's budget will be made zero for the remainder of the server's

   period, and the implementation will not replenish the budget until

   the specified synchronization object is signalled. At that time,

   all pending budget replenishments (if any) are made effective. Once

   the server has a positive budget and the scheduler schedules the

   calling thread again, the call returns and at that time, except for

   those parameters equal to NULL pointers, the system reports the

   current period and budget for the current job, whether the deadline

   of the previous job was missed or not, and whether the budget of

   the previous job was overrun or not.

   In a system with hierarchical scheduling, since this call makes the

   budget zero, the other threads in the same server are not run. As

   mentioned above, only when the call finishes the budget may be

   replenished.

    [ERR@RETURNED:

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_INTERNAL_ERROR : erroneous binding or malfunction of the FSF

       main scheduler

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not scheduled

       under the FSF

     FSF_ERR_NOT_BOUND_THREAD : if the calling thread does not have a valid

       server bound to it

     FSF_ERR_BAD_ARGUMENT :  if the synch_handle given is not valid

     FSF_ERR_SERVER_WORKLOAD_NOT_COMPATIBLE: if the kind of workload of the server

       is not FSF_BOUNDED

    ]

*/

int

fsf_schedule_triggered_job

  (fsf_synch_obj_handle_t  synch_handle,

   struct timespec         *next_budget,

   struct timespec         *next_period,

   bool                    *was_deadline_missed,

   bool                    *was_budget_overran);

/**

   This call is the same as fsf_schedule_triggered_job, but with an

   absolute timeout. The timed_out argument, indicates whether the

   function returned because of a timeout or not

    [ERR@RETURNED:

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_INTERNAL_ERROR : erroneous binding or malfunction of the FSF

       main scheduler

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not scheduled

       under the FSF

     FSF_ERR_NOT_BOUND_THREAD : if the calling thread does not have a valid

       server bound to it

     FSF_ERR_BAD_ARGUMENT :  if the synch_handle given is not valid or the

       abs_timeout argument is NULL or its value is in the past

     FSF_ERR_SERVER_WORKLOAD_NOT_COMPATIBLE: if the kind of workload of the server

       is not FSF_BOUNDED

    ]

*/

int

fsf_timed_schedule_triggered_job

  (fsf_synch_obj_handle_t  synch_handle,

   const struct timespec   *abs_timeout,

   bool                    *timed_out,

   struct timespec         *next_budget,

   struct timespec         *next_period,

   bool                    *was_deadline_missed,

   bool                    *was_budget_overran);

/*@}*/

///////////////////////////////////////////////////////////////////

//                 CONTRACT NEGOCIATION OPERATIONS

///////////////////////////////////////////////////////////////////

/**

   \defgroup negotiate Negotiate contract functions

   The following functions are used to create servers for a contract

   parameters specification and also to assign one or more threads to

   a server (Note: the current implementation only supports one thread

   per server; this limitation will be removed in the next phase of

   the project)

*/

/*@{*/

/**

    Server Id type, that identifies a server created to manage a given

    contract

*/

typedef int      fsf_server_id_t;             // => 0

/**

    The type references a function that may become a thread's

    code

*/

typedef void * (*fsf_thread_code_t) (void *);

/**

   The operation negotiates a contract for a new server. If the

   on-line admission test is enabled it determines whether the

   contract can be admitted or not based on the current contracts

   established in the system. Then it creates the server and

   recalculates all necessary parameters for the contracts already

   present in the system. This is a potentially blocking operation; it

   returns when the system has either rejected the contract, or

   admitted it and made it effective. It returns zero and places the

   server identification number in the location pointed to by the

   server input parameter if accepted, or an error if rejected.  No

   thread is bound to the newly created server, which will be idle

   until a thread is bound to it. This operation can only be executed

   by threads that are already bound to an active server and therefore

   are being scheduled by the fsf scheduler.

    [ERR@RETURNED:

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_INTERNAL_ERROR : erroneous binding or malfunction of the FSF

       main scheduler

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not scheduled

       under the FSF

     FSF_ERR_BAD_ARGUMENT :  if the contract or server arguments are NULL

     FSF_ERR_TOO_MANY_SERVERS : if there is no space for more servers

       (the maximum number of them is already reached)

    ]

*/

int

fsf_negotiate_contract

  (const fsf_contract_parameters_t *contract,

   fsf_server_id_t      *server);

/**

   This operation negotiates a contract for a new server, creates a

   thread and binds it to the server. If the contract is accepted, the

   operation creates a thread with the arguments thread, attr,

   thread_code and arg as they are defined for the pthread_create()

   POSIX function call, and attaches it to the fsf scheduler. Then, it

   binds the created thread to the new server. It returns zero and

   puts the server identification number in the location pointed to by

   the server input parameter. The attr parameter is overwritten as

   necessary to introduce the adequate scheduling policy and priority,

   according to the preemption level given in the contract and the

   fsf_priority_map() function defined by the user. If the contract is

   rejected, the thread is not created and the corresponding error is

   returned.

   The server is created with the FSF_NONE scheduling policy, which

   means no hierarchical scheduling, and only one thread per server,

   except for the case of background tasks (see below)

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT : if the contract or server arguments are NULL

     FSF_ERR_CONTRACT_REJECTED : if the contract is rejected.

     FSF_ERR_SERVER_WORKLOAD_NOT_COMPATIBLE: if the kind of workload

       in the contract is FSF_OVERHEAD

     It may also return all the errors that may be returned by the

       pthread_create()POSIX function call

    ]

*/

int

fsf_negotiate_contract_for_new_thread

  (const fsf_contract_parameters_t *contract,

   fsf_server_id_t      *server,

   pthread_t            *thread,

   pthread_attr_t       *attr,

   fsf_thread_code_t     thread_code,

   void                 *arg);

/**

   This operation negotiates a contract for a new server, and binds

   the calling thread to it. If the contract is accepted it returns

   zero and copies the server identification number in the location

   pointed to by the server input parameter.  If it is rejected, an

   error is returned.

   The server is created with the FSF_NONE scheduling policy, which

   means no hierarchical scheduling, and only one thread per server,

   except for the case of background tasks (see below)

   Implementation dependent issue: In order to allow the usage of

   application defined schedulers, the calling thread must not have

   the SCHED_APP scheduling policy and at the same time be attached to

   an application scheduler different than the fsf scheduler; in such

   case, an error is returned. After a successful call the calling

   thread will have the SCHED_APP scheduling policy and will be

   attached to the fsf scheduler.

    [ERR@RETURNED:

     FSF_ERR_UNKNOWN_APPSCHEDULED_THREAD : if the thread is attached to

       an application defined scheduler different than the fsf scheduler

     FSF_ERR_BAD_ARGUMENT :  if the contract or server arguments are NULL

     FSF_ERR_CONTRACT_REJECTED : if the contract is rejected.

     FSF_ERR_SERVER_WORKLOAD_NOT_COMPATIBLE: if the kind of workload

       in the contract is FSF_OVERHEAD

    ]

*/

int

fsf_negotiate_contract_for_myself

  (const fsf_contract_parameters_t *contract,

   fsf_server_id_t      *server);

/**

   fsf_bind_thread_to_server: This operation associates a thread with

   a server, which means that it starts consuming the server's budget

   and is executed according to the contract established for that

   server. If the thread is already bound to another server, it is

   effectively unbound from it and bound to the specified one.

   It fails if the server's policy is different than FSF_NONE, or if

   there is already a thread bound to this server

   Implementation dependent issue: In order to allow the usage of

   application defined schedulers, the given thread must not have the

   scheduling policy SCHED_APP and at the same time be attached to an

   application scheduler different than the fsf scheduler.

    [ERR@RETURNED:

     FSF_ERR_INTERNAL_ERROR : erroneous binding or malfunction of the FSF

       main scheduler

     FSF_ERR_UNKNOWN_APPSCHEDULED_THREAD : if the thread is attached to

       an application defined scheduler different than the fsf scheduler

     FSF_ERR_BAD_ARGUMENT : if the server value does not complain with the

       expected format or valid range or the given thread does not exist

     FSF_ERR_NOT_CONTRACTED_SERVER : if the referenced server is not valid

     FSF_ERR_SERVER_WORKLOAD_NOT_COMPATIBLE: if the kind of workload

       of the server is FSF_OVERHEAD

     FSF_ERR_ALREADY_BOUND : if the given server has a thread already bound

    ]

*/

int

fsf_bind_thread_to_server

  (fsf_server_id_t server,

   pthread_t       thread);

/**

   This operation unbinds a thread from a server.  Since threads with

   no server associated are not allow to execute, they remain in a

   dormant state until they are either eliminated or bound again.

   If the thread is inside a critical section the effects of this call

   are deferred until the critical section is ended

   Implementation dependent issue: in the implementation with an

   application scheduler, the thread is still attached to the fsf

   scheduler, but suspended.

    [ERR@RETURNED:

     FSF_ERR_INTERNAL_ERROR : erroneous binding or malfunction of the FSF

       main scheduler

     FSF_ERR_BAD_ARGUMENT : if the given thread does not exist

     FSF_ERR_NOT_SCHEDULED_THREAD : if the given thread is not scheduled

       under the FSF

     FSF_ERR_UNKNOWN_APPSCHEDULED_THREAD : if the thread is attached to

       an application defined scheduler different than the fsf scheduler

     FSF_ERR_NOT_BOUND_THREAD : if the given thread does not have a valid

       server bound to it

    ]

*/

int

fsf_unbind_thread_from_server (pthread_t thread);

/**

   This operation stores the Id of the server associated with the

   specified thread in the variable pointed to by server. It returns

   an error if the thread does not exist, it is not under the control

   of the scheduling framework, or is not bound.

    [ERR@RETURNED:

     FSF_ERR_NOT_SCHEDULED_THREAD : if the given thread is not scheduled

       under the FSF

     FSF_ERR_NOT_BOUND_THREAD : if the given thread does not have a valid

       server bound to it

     FSF_ERR_BAD_ARGUMENT : if the given thread does not exist or the

       server argument is NULL

    ]

*/

int

fsf_get_server

  (pthread_t       thread,

   fsf_server_id_t *server);

/**

   This operation stores the contract parameters currently associated

   with the specified server in the variable pointed to by

   contract. It returns an error if the server id is incorrect.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if the contract argument is NULL or the value

       of the server argument is not in range

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_NOT_CONTRACTED_SERVER : if the server of the calling thread

       has been cancelled or it is not valid

    ]

*/

int

fsf_get_contract

   (fsf_server_id_t server,

    fsf_contract_parameters_t *contract);

/**

   The operation eliminates the specified server

   and recalculates all necessary parameters for the contracts

   remaining in the system. This is a potentially blocking operation;

   it returns when the system has made the changes effective.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if the value of server is not in range

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_NOT_CONTRACTED_SERVER : if the server of the calling thread

       has been cancelled or it is not valid

    ]

*/

int

fsf_cancel_contract (fsf_server_id_t server);

/**

   The operation renegotiates a contract for an existing server. If

   the on-line admission test is enabled it determines whether the

   contract can be admitted or not based on the current contracts

   established in the system. If it cannot be admitted, the old

   contract remains in effect and an error is returned. If it can be

   admitted, it recalculates all necessary parameters for the

   contracts already present in the system anr returns zero. This is a

   potentially blocking operation; it returns when the system has

   either rejected the new contract, or admitted it and made it

   effective.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if the new_contract argument is NULL or the  

       value of the server argument is not in range

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_NOT_CONTRACTED_SERVER : if the server of the calling thread

       has been cancelled or it is not valid

    ]

*/

int

fsf_renegotiate_contract

  (const fsf_contract_parameters_t *new_contract,

   fsf_server_id_t server);

/**

   The operation enqueues a renegotiate operation for an existing

   server, and returns immediately. The renegotiate operation is

   performed asynchronously, as soon as it is practical; meanwhile the

   system operation will continue normally. When the renegotiation is

   made, if the on-line admission test is enabled it determines

   whether the contract can be admitted or not based on the current

   contracts established in the system. If it cannot be admitted, the

   old contract remains in effect. If it can be admitted, it

   recalculates all necessary parameters for the contracts already

   present in the system. When the operation is completed,

   notification is made to the caller, if requested, via a signal. The

   status of the operation (in progress, admitted, rejected) can be

   checked with the get_renegotiation_status operation.  The argument

   sig_notify can be NULL_SIGNAL (no notification), or any posix

   signal; and in this case sig_value is to be sent with the signal.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if the new_contract argument is NULL, the  

       value of the server argument is not in range or sig_notify is

       neither NULL nor a valid POSIX signal

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_NOT_CONTRACTED_SERVER : if the server of the calling thread

       has been cancelled or it is not valid

    ]

*/

int

fsf_request_contract_renegotiation

  (const fsf_contract_parameters_t *new_contract,

   fsf_server_id_t                  server,

   int                              sig_notify,

   union sigval                     sig_value);

/**

   The operation reports on the status of the last renegotiation

   operation enqueued for the specified server. It is callable even

   after notification of the completion of such operation, if

   requested. If the fsf_request_contract_renegotiation operation has

   not ever been called for the given server the status returned is

   FSF_NOT_REQUESTED

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT :  if the renegotiation_status argument is

       NULL or the value of the server argument is not in range

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_NOT_CONTRACTED_SERVER : if the server of the calling thread

       has been cancelled or it is not valid

    ]

*/

int

fsf_get_renegotiation_status

  (fsf_server_id_t server,

   fsf_renegotiation_status_t *renegotiation_status);

/*@}*/

////////////////////////////////////////////////////

//           OBTAINING INFORMATION FROM THE SCHEDULER

////////////////////////////////////////////////////

/**

   Returns true if the system is

   configured with the on-line admission test enabled, or false

   otherwise.

*/

bool

fsf_is_admission_test_enabled();

/**

   This function stores the current execution time spent by the

   threads bound to the specified server in the variable pointed to by

   cpu_time.

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT : if the value of the server argument is not in range or

       cpu_time is NULL

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_NOT_CONTRACTED_SERVER : if the server of the calling thread

       has been cancelled or it is not valid

    ]

*/

int

fsf_get_cpu_time

   (fsf_server_id_t server,

    struct timespec *cpu_time);

/**

   This function stores in the variable pointed to by budget the

   remaining execution-time budget associated with the specified

   server

    [ERR@RETURNED:

     FSF_ERR_BAD_ARGUMENT : if the value of the server argument is not in range or

       budget is NULL

     FSF_ERR_NOT_SCHEDULED_CALLING_THREAD : if the calling thread is not

       scheduled under the FSF

     FSF_ERR_INVALID_SCHEDULER_REPLY : the scheduler is wrong or not running

     FSF_ERR_NOT_CONTRACTED_SERVER : if the server of the calling thread

       has been cancelled or it is not valid

    ]

*/

int

fsf_get_remaining_budget

   (fsf_server_id_t server,

    struct timespec *budget);

/**

   This function stores in the variables

   pointed to by budget and period, the execution-time budget and the

   period respectively associated with the specified server. If any of

   these pointers is NULL, the corresponding information is not stored.