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501 lines
12 KiB
C
501 lines
12 KiB
C
/*
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* pthread_mutex.c
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*
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* Description:
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* This translation unit implements mutual exclusion (mutex) primitives.
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*
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* --------------------------------------------------------------------------
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*
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* Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
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* Copyright(C) 2008 Jason Schmidlapp
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*
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* Contact Email: jschmidlapp@users.sourceforge.net
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*
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*
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* Based upon Pthreads-win32 - POSIX Threads Library for Win32
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* Copyright(C) 1998 John E. Bossom
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* Copyright(C) 1999,2005 Pthreads-win32 contributors
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*
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* Contact Email: rpj@callisto.canberra.edu.au
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*
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* The original list of contributors to the Pthreads-win32 project
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* is contained in the file CONTRIBUTORS.ptw32 included with the
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* source code distribution. The list can also be seen at the
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* following World Wide Web location:
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* http://sources.redhat.com/pthreads-win32/contributors.html
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library 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 GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library in the file COPYING.LIB;
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* if not, write to the Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <pte_osal.h>
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#include "pthread.h"
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#include "implement.h"
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#define TEST_IE InterlockedExchange
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int pthread_mutex_destroy (pthread_mutex_t * mutex)
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{
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int result = 0;
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pthread_mutex_t mx;
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/*
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* Let the system deal with invalid pointers.
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*/
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/*
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* Check to see if we have something to delete.
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*/
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if (*mutex < PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
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{
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mx = *mutex;
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result = pthread_mutex_trylock (&mx);
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/*
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* If trylock succeeded and the mutex is not recursively locked it
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* can be destroyed.
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*/
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if (result == 0)
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{
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if (mx->kind != PTHREAD_MUTEX_RECURSIVE || 1 == mx->recursive_count)
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{
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/*
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* FIXME!!!
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* The mutex isn't held by another thread but we could still
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* be too late invalidating the mutex below since another thread
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* may already have entered mutex_lock and the check for a valid
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* *mutex != NULL.
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*
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* Note that this would be an unusual situation because it is not
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* common that mutexes are destroyed while they are still in
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* use by other threads.
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*/
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*mutex = NULL;
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result = pthread_mutex_unlock (&mx);
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if (result == 0)
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{
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pte_osSemaphoreDelete(mx->handle);
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free(mx);
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}
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else
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{
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/*
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* Restore the mutex before we return the error.
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*/
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*mutex = mx;
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}
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}
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else /* mx->recursive_count > 1 */
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{
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/*
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* The mutex must be recursive and already locked by us (this thread).
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*/
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mx->recursive_count--; /* Undo effect of pthread_mutex_trylock() above */
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result = EBUSY;
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}
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}
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}
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else
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{
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/*
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* See notes in pte_mutex_check_need_init() above also.
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*/
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pte_osMutexLock (pte_mutex_test_init_lock);
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/*
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* Check again.
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*/
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if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
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{
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/*
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* This is all we need to do to destroy a statically
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* initialised mutex that has not yet been used (initialised).
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* If we get to here, another thread
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* waiting to initialise this mutex will get an EINVAL.
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*/
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*mutex = NULL;
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}
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else
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{
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/*
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* The mutex has been initialised while we were waiting
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* so assume it's in use.
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*/
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result = EBUSY;
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}
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pte_osMutexUnlock(pte_mutex_test_init_lock);
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}
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return (result);
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}
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int pthread_mutex_init (pthread_mutex_t * mutex, const pthread_mutexattr_t * attr)
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{
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int result = 0;
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pthread_mutex_t mx;
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if (mutex == NULL)
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return EINVAL;
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mx = (pthread_mutex_t) calloc (1, sizeof (*mx));
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if (mx == NULL)
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result = ENOMEM;
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else
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{
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mx->lock_idx = 0;
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mx->recursive_count = 0;
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mx->kind = (attr == NULL || *attr == NULL
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? PTHREAD_MUTEX_DEFAULT : (*attr)->kind);
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mx->ownerThread = NULL;
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pte_osSemaphoreCreate(0,&mx->handle);
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}
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*mutex = mx;
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return (result);
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}
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int pthread_mutex_lock (pthread_mutex_t * mutex)
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{
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int result = 0;
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pthread_mutex_t mx;
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/*
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* Let the system deal with invalid pointers.
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*/
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if (*mutex == NULL)
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return EINVAL;
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/*
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* We do a quick check to see if we need to do more work
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* to initialise a static mutex. We check
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* again inside the guarded section of pte_mutex_check_need_init()
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* to avoid race conditions.
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*/
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if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
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{
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if ((result = pte_mutex_check_need_init (mutex)) != 0)
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return (result);
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}
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mx = *mutex;
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if (mx->kind == PTHREAD_MUTEX_NORMAL)
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{
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if (PTE_ATOMIC_EXCHANGE(
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&mx->lock_idx,
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1) != 0)
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{
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while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
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{
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if (pte_osSemaphorePend(mx->handle,NULL) != PTE_OS_OK)
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{
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result = EINVAL;
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break;
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}
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}
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}
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}
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else
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{
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pthread_t self = pthread_self();
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if (PTE_ATOMIC_COMPARE_EXCHANGE(&mx->lock_idx,1,0) == 0)
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{
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mx->recursive_count = 1;
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mx->ownerThread = self;
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}
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else
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{
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if (pthread_equal (mx->ownerThread, self))
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{
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if (mx->kind == PTHREAD_MUTEX_RECURSIVE)
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mx->recursive_count++;
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else
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result = EDEADLK;
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}
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else
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{
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while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
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{
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if (pte_osSemaphorePend(mx->handle,NULL) != PTE_OS_OK)
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{
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result = EINVAL;
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break;
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}
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}
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if (0 == result)
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{
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mx->recursive_count = 1;
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mx->ownerThread = self;
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}
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}
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}
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}
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return (result);
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}
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static int pte_timed_eventwait (pte_osSemaphoreHandle event, const struct timespec *abstime)
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/*
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* ------------------------------------------------------
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* DESCRIPTION
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* This function waits on an event until signaled or until
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* abstime passes.
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* If abstime has passed when this routine is called then
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* it returns a result to indicate this.
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*
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* If 'abstime' is a NULL pointer then this function will
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* block until it can successfully decrease the value or
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* until interrupted by a signal.
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*
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* This routine is not a cancelation point.
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*
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* RESULTS
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* 0 successfully signaled,
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* ETIMEDOUT abstime passed
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* EINVAL 'event' is not a valid event,
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*
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* ------------------------------------------------------
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*/
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{
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unsigned int milliseconds;
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pte_osResult status;
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int retval;
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if (abstime == NULL)
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status = pte_osSemaphorePend(event, NULL);
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else
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{
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/*
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* Calculate timeout as milliseconds from current system time.
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*/
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milliseconds = pte_relmillisecs (abstime);
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status = pte_osSemaphorePend(event, &milliseconds);
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}
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if (status == PTE_OS_TIMEOUT)
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{
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retval = ETIMEDOUT;
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}
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else
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{
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retval = 0;
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}
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return retval;
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}
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int pthread_mutex_timedlock (pthread_mutex_t * mutex,
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const struct timespec *abstime)
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{
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int result;
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pthread_mutex_t mx;
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/*
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* Let the system deal with invalid pointers.
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*/
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/*
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* We do a quick check to see if we need to do more work
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* to initialise a static mutex. We check
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* again inside the guarded section of pte_mutex_check_need_init()
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* to avoid race conditions.
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*/
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if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
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{
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if ((result = pte_mutex_check_need_init (mutex)) != 0)
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return (result);
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}
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mx = *mutex;
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if (mx->kind == PTHREAD_MUTEX_NORMAL)
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{
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if (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,1) != 0)
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{
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while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
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{
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if (0 != (result = pte_timed_eventwait (mx->handle, abstime)))
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return result;
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}
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}
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}
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else
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{
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pthread_t self = pthread_self();
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if (PTE_ATOMIC_COMPARE_EXCHANGE(&mx->lock_idx,1,0) == 0)
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{
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mx->recursive_count = 1;
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mx->ownerThread = self;
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}
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else
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{
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if (pthread_equal (mx->ownerThread, self))
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{
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if (mx->kind == PTHREAD_MUTEX_RECURSIVE)
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mx->recursive_count++;
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else
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return EDEADLK;
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}
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else
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{
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while (PTE_ATOMIC_EXCHANGE(&mx->lock_idx,-1) != 0)
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{
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if (0 != (result = pte_timed_eventwait (mx->handle, abstime)))
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return result;
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}
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mx->recursive_count = 1;
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mx->ownerThread = self;
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}
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}
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}
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return 0;
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}
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int pthread_mutex_trylock (pthread_mutex_t * mutex)
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{
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int result = 0;
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pthread_mutex_t mx;
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/*
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* Let the system deal with invalid pointers.
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*/
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/*
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* We do a quick check to see if we need to do more work
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* to initialise a static mutex. We check
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* again inside the guarded section of pte_mutex_check_need_init()
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* to avoid race conditions.
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*/
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if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
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{
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if ((result = pte_mutex_check_need_init (mutex)) != 0)
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return (result);
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}
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mx = *mutex;
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if (0 == PTE_ATOMIC_COMPARE_EXCHANGE (&mx->lock_idx,1,0))
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{
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if (mx->kind != PTHREAD_MUTEX_NORMAL)
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{
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mx->recursive_count = 1;
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mx->ownerThread = pthread_self ();
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}
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}
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else
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{
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if (mx->kind == PTHREAD_MUTEX_RECURSIVE &&
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pthread_equal (mx->ownerThread, pthread_self ()))
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mx->recursive_count++;
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else
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result = EBUSY;
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}
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return (result);
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}
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int pthread_mutex_unlock (pthread_mutex_t * mutex)
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{
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int result = 0;
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pthread_mutex_t mx = *mutex;
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/*
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* Let the system deal with invalid pointers.
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*/
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/*
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* If the thread calling us holds the mutex then there is no
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* race condition. If another thread holds the
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* lock then we shouldn't be in here.
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*/
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if (mx < PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
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{
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if (mx->kind == PTHREAD_MUTEX_NORMAL)
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{
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int idx;
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idx = PTE_ATOMIC_EXCHANGE (&mx->lock_idx,0);
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if (idx != 0)
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{
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if (idx < 0)
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{
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/*
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* Someone may be waiting on that mutex.
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*/
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if (pte_osSemaphorePost(mx->handle,1) != PTE_OS_OK)
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result = EINVAL;
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}
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}
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else
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{
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/*
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* Was not locked (so can't be owned by us).
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*/
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result = EPERM;
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}
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}
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else
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{
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if (pthread_equal (mx->ownerThread, pthread_self ()))
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{
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if (mx->kind != PTHREAD_MUTEX_RECURSIVE
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|| 0 == --mx->recursive_count)
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{
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mx->ownerThread = NULL;
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if (PTE_ATOMIC_EXCHANGE (&mx->lock_idx,0) < 0)
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{
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if (pte_osSemaphorePost(mx->handle,1) != PTE_OS_OK)
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result = EINVAL;
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}
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}
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}
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else
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result = EPERM;
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}
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}
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else
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result = EINVAL;
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return (result);
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}
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