142 lines
4.3 KiB
C
142 lines
4.3 KiB
C
/* Copyright (C) 2004 David Decotigny
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
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USA.
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*/
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#ifndef _SOS_SCHED_H_
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#define _SOS_SCHED_H_
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/**
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* @file sched.h
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*
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* A basic scheduler inspired from the O(1) Linux scheduler. Supports
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* 2 classes of thread priorities:
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* - so-called 'real-time' threads scheduled according to a simple
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* traditional static priority real-time scheduler. "Real-time" round
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* robin scheduling is not supported.
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* - "fair" time-sharing scheduling for non real-time threads. "fair"
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* because no starvation among the non real-time threads is
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* possible. Contrary to the original O(1) Linux scheduler, the
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* on-line adjustment of the scheduling priorities to cope with
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* interactive/non interactive threads discrimination is not
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* supported: threads keep having the same priority as long as the
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* user does not change it.
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*
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* The functions below manage CPU queues, and are NEVER responsible
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* for context switches (see thread.h for that) or synchronizations
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* (see kwaitq.h or the higher levels primitives [mutex, semaphore,
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* ...] for that).
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*
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* @note IMPORTANT: all the functions below are meant to be called
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* ONLY by the thread/timer/kwaitq subsystems. DO NOT use them
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* directly from anywhere else: use ONLY the thread/kwaitq functions!
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* If you still want to call them directly despite this disclaimer,
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* simply disable interrupts before clling them.
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*/
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#include <sos/errno.h>
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/**
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* The definition of a priority
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*/
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typedef unsigned char sos_sched_priority_t;
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#include <sos/thread.h>
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/**
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* Valid priority interval ("real-time" and non real-time threads altogether)
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*/
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#define SOS_SCHED_PRIO_HIGHEST 0
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#define SOS_SCHED_PRIO_LOWEST 63
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#define SOS_SCHED_NUM_PRIO 64
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/**
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* Class-specific priorities
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*/
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#define SOS_SCHED_PRIO_RT_HIGHEST 0 /**< Highest 'real-time' static prio. */
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#define SOS_SCHED_PRIO_RT_LOWEST 15 /**< Lowest 'real-time' static priority */
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#define SOS_SCHED_PRIO_TS_HIGHEST 16 /**< Highest time-sharing priority */
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#define SOS_SCHED_PRIO_TS_LOWEST 63 /**< Lowest time-sharing priority */
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#define SOS_SCHED_PRIO_DEFAULT 40 /**< Default priority */
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/**
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* Helper macros (Yes, priorities ordered in decreasing numerical value)
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*
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* @note: The use of this function is RESERVED
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*/
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#define SOS_SCHED_PRIO_CMP(prio1,prio2) ((prio1) - (prio2))
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#define SOS_SCHED_PRIO_IS_VALID(prio) \
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({ int __prio = (int)(prio); \
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((__prio) <= SOS_SCHED_PRIO_LOWEST) \
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&& \
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((__prio) >= SOS_SCHED_PRIO_HIGHEST); })
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#define SOS_SCHED_PRIO_IS_RT(prio) \
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({ int __prio = (int)(prio); \
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((__prio) <= SOS_SCHED_PRIO_RT_LOWEST) \
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&& \
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((__prio) >= SOS_SCHED_PRIO_RT_HIGHEST); })
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/**
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* Initialize the scheduler
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*
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* @note: The use of this function is RESERVED
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*/
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sos_ret_t sos_sched_subsystem_setup();
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/**
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* Mark the given thread as ready
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*
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* @note: The use of this function is RESERVED
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*/
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sos_ret_t sos_sched_set_ready(struct sos_thread * thr);
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/**
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* Return the identifier of the next thread to run. Also removes it
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* from the ready list, but does NOT set is as current_thread !
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*
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* @param current_thread TCB of the thread calling the function
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*
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* @param do_yield When TRUE, put the current executing thread at the
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* end of the ready list. Otherwise it is kept at the head of it.
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*
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* @note: The use of this function is RESERVED
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*/
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struct sos_thread * sos_reschedule(struct sos_thread * current_thread,
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sos_bool_t do_yield);
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/**
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* Called by thread subsystem each time a READY thread's priority is
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* changed
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*
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* @note: The use of this function is RESERVED (to thread.c)
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*/
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sos_ret_t sos_sched_change_priority(struct sos_thread * thr,
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sos_sched_priority_t priority);
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#endif /* _SOS_WAITQUEUE_H_ */
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