153 lines
4.3 KiB
C
153 lines
4.3 KiB
C
/***************************************************************************
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* __________ __ ___.
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* Open \______ \ ____ ____ | | _\_ |__ _______ ___
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* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
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* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
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* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
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* \/ \/ \/ \/ \/
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* $Id$
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*
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* Copyright (C) 2002 by Björn Stenberg
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*
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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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*
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* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
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* KIND, either express or implied.
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*
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****************************************************************************/
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/****************************************************************************
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* Simple mutex functions ;)
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****************************************************************************/
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#include <stdbool.h>
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#include "config.h"
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#include "system.h"
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#include "mutex.h"
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#include "corelock.h"
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#include "thread-internal.h"
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#include "kernel-internal.h"
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static inline void __attribute__((always_inline))
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mutex_set_thread(struct mutex *mtx, struct thread_entry *td)
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{
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#ifdef HAVE_PRIORITY_SCHEDULING
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mtx->blocker.thread = td;
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#else
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mtx->thread = td;
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#endif
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}
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static inline struct thread_entry * __attribute__((always_inline))
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mutex_get_thread(volatile struct mutex *mtx)
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{
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#ifdef HAVE_PRIORITY_SCHEDULING
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return mtx->blocker.thread;
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#else
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return mtx->thread;
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#endif
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}
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/* Initialize a mutex object - call before any use and do not call again once
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* the object is available to other threads */
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void mutex_init(struct mutex *m)
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{
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corelock_init(&m->cl);
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m->queue = NULL;
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m->recursion = 0;
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mutex_set_thread(m, NULL);
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#ifdef HAVE_PRIORITY_SCHEDULING
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m->blocker.priority = PRIORITY_IDLE;
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m->blocker.wakeup_protocol = wakeup_priority_protocol_transfer;
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m->no_preempt = false;
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#endif
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}
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/* Gain ownership of a mutex object or block until it becomes free */
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void mutex_lock(struct mutex *m)
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{
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struct thread_entry *current = thread_self_entry();
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if(current == mutex_get_thread(m))
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{
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/* current thread already owns this mutex */
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m->recursion++;
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return;
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}
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/* lock out other cores */
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corelock_lock(&m->cl);
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/* must read thread again inside cs (a multiprocessor concern really) */
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if(LIKELY(mutex_get_thread(m) == NULL))
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{
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/* lock is open */
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mutex_set_thread(m, current);
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corelock_unlock(&m->cl);
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return;
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}
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/* block until the lock is open... */
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IF_COP( current->obj_cl = &m->cl; )
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IF_PRIO( current->blocker = &m->blocker; )
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current->bqp = &m->queue;
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disable_irq();
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block_thread(current);
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corelock_unlock(&m->cl);
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/* ...and turn control over to next thread */
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switch_thread();
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}
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/* Release ownership of a mutex object - only owning thread must call this */
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void mutex_unlock(struct mutex *m)
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{
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/* unlocker not being the owner is an unlocking violation */
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KERNEL_ASSERT(mutex_get_thread(m) == thread_self_entry(),
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"mutex_unlock->wrong thread (%s != %s)\n",
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mutex_get_thread(m)->name,
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thread_self_entry()->name);
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if(m->recursion > 0)
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{
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/* this thread still owns lock */
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m->recursion--;
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return;
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}
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/* lock out other cores */
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corelock_lock(&m->cl);
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/* transfer to next queued thread if any */
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if(LIKELY(m->queue == NULL))
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{
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/* no threads waiting - open the lock */
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mutex_set_thread(m, NULL);
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corelock_unlock(&m->cl);
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return;
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}
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else
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{
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const int oldlevel = disable_irq_save();
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/* Tranfer of owning thread is handled in the wakeup protocol
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* if priorities are enabled otherwise just set it from the
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* queue head. */
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IFN_PRIO( mutex_set_thread(m, m->queue); )
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IF_PRIO( unsigned int result = ) wakeup_thread(&m->queue);
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restore_irq(oldlevel);
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corelock_unlock(&m->cl);
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#ifdef HAVE_PRIORITY_SCHEDULING
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if((result & THREAD_SWITCH) && !m->no_preempt)
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switch_thread();
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#endif
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}
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}
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