533d396761
Any number of readers may be in the critical section at a time and writers are mutually exclusive to all other threads. They are a better choice when data is rarely modified but often read and multiple threads can safely access it for reading. Priority inheritance is fully implemented along with other changes to the kernel to fully support it on multiowner objects. This also cleans up priority code in the kernel and updates some associated structures in existing objects to the cleaner form. Currently doesn't add the mrsw_lock.[ch] files since they're not yet needed by anything but the supporting improvements are still useful. This includes a typed bitarray API (bitarray.h) which is pretty basic for now. Change-Id: Idbe43dcd9170358e06d48d00f1c69728ff45b0e3 Reviewed-on: http://gerrit.rockbox.org/801 Reviewed-by: Michael Sevakis <jethead71@rockbox.org> Tested: Michael Sevakis <jethead71@rockbox.org>
129 lines
3.8 KiB
C
129 lines
3.8 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 "kernel.h"
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#include "thread-internal.h"
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#include "kernel-internal.h"
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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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m->blocker.thread = NULL;
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#ifdef HAVE_PRIORITY_SCHEDULING
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m->blocker.priority = PRIORITY_IDLE;
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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 == m->blocker.thread)
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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(m->blocker.thread == NULL))
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{
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/* lock is open */
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m->blocker.thread = 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, TIMEOUT_BLOCK);
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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(m->blocker.thread == thread_self_entry(),
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"mutex_unlock->wrong thread (%s != %s)\n",
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m->blocker.thread->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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m->blocker.thread = NULL;
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corelock_unlock(&m->cl);
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return;
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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( m->blocker.thread = m->queue; )
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unsigned int result = wakeup_thread(&m->queue, WAKEUP_TRANSFER);
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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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(void)result;
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}
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