source: trunk/sys/libpthread/pthread_mutex.c@ 17

/*
 * pthread_mutex.c - pthread mutex related functions
 * 
 * Copyright (c) 2008,2009,2010,2011,2012 Ghassan Almaless
 * Copyright (c) 2011,2012 UPMC Sorbonne Universites
 *
 * This file is part of ALMOS.
 *
 * ALMOS is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2.0 of the License.
 *
 * ALMOS is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with ALMOS; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <errno.h>
#include <sys/types.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
#include <sys/syscall.h>
#include <cpu-syscall.h>
#include <assert.h>
#include <unistd.h>

#define USE_PTSPINLOCK       1
#define USE_HEURISTIC_LOCK   0
//#define CONFIG_MUTEX_DEBUG

#ifdef CONFIG_MUTEX_DEBUG
#define mdmsg(...) fprintf(stderr, __VA_ARGS__)
#else
#define mdmsg(...)
#endif

#define print_mutex(x)                                                  \
        do{mdmsg("%s: mtx @%x, [v %u, w %d, t %d, s %d, c %d]\n",       \
                 __FUNCTION__,                                          \
                 (unsigned)(x),                                         \
                 (unsigned)(x)->value,                                  \
                 (unsigned)(x)->waiting,                                \
                 (x)->attr.type,                                        \
                 (x)->attr.scope,                                       \
                 (x)->attr.cntr);}while(0)

int pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
        if(attr == NULL) return EINVAL;
  
        attr->type  = PTHREAD_MUTEX_DEFAULT;
        attr->scope = PTHREAD_PROCESS_PRIVATE;
        attr->cntr  = 0;
        return 0;
}

int pthread_mutexattr_setpshared(pthread_mutexattr_t *attr, int pshared)
{
        if((attr == NULL) || ((pshared != PTHREAD_PROCESS_SHARED) && (pshared != PTHREAD_PROCESS_PRIVATE)))
                return EINVAL;
  
        attr->scope = attr->scope;
        return 0;
}

int pthread_mutexattr_getpshared(pthread_mutexattr_t *attr, int *pshared)
{
        if(attr == NULL)
                return EINVAL;
  
        *pshared = (int)attr->scope;
        return 0;
}

int pthread_mutexattr_gettype(pthread_mutexattr_t *attr, int *type)
{
        if(attr == NULL)
                return EINVAL;

        *type = (int)attr->type;
        return 0;
}

int pthread_mutexattr_settype(pthread_mutexattr_t *attr, int type)
{
        if(attr == NULL)
                return EINVAL;
  
        if(type == PTHREAD_MUTEX_RECURSIVE)
                attr->type = (uint8_t)type;
        else
                attr->type = PTHREAD_MUTEX_DEFAULT;

        return 0;
}

int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
{
        return 0;
}

int pthread_mutex_init (pthread_mutex_t *mutex, const pthread_mutexattr_t * attr)
{
        int err;
        pthread_mutexattr_t _attr;

        if(mutex == NULL)
                return EINVAL;

        if(attr == NULL)
        {
                pthread_mutexattr_init(&_attr);
                attr = &_attr;
        }

        err = pthread_spin_init(&mutex->lock, 0);

        if(err) return err;

        mutex->value      = __PTHREAD_OBJECT_FREE;
        mutex->waiting    = 0;
        mutex->attr.type  = attr->type;
        mutex->attr.scope = attr->scope;
        mutex->attr.cntr  = attr->cntr;

        if(mutex->attr.scope == PTHREAD_PROCESS_SHARED)
                return sem_init(&mutex->sem, PTHREAD_PROCESS_SHARED, 1);

        return 0;
}

int pthread_mutex_lock (pthread_mutex_t *mutex)
{
        volatile uint_t cntr;
        register __pthread_tls_t *tls;
        register uint_t this;
        register const uint_t limit1 = 100000;
        register const uint_t limit2 = 2 * limit1;
        int err;
  
        if(mutex == NULL)
                return EINVAL;

        cntr = 0;
        this = (uint_t)pthread_self();
        int pid = getpid();

        if(mutex->value == __PTHREAD_OBJECT_DESTROYED)
                return EINVAL;

        if((mutex->attr.type == PTHREAD_MUTEX_RECURSIVE) && (mutex->value == this))
        {
                mutex->attr.cntr += 1;
                return 0;
        }

        if(mutex->value == this)
                return EDEADLK;

        if(mutex->attr.scope == PTHREAD_PROCESS_SHARED)
                return sem_wait(&mutex->sem);

        for(cntr = 0; ((cntr < limit2) && (mutex->value != __PTHREAD_OBJECT_FREE)); cntr++)
        {
                if((cntr > limit1) && (mutex->value != __PTHREAD_OBJECT_FREE))// && (mutex->waiting > 4))
                        break;
        }

#if USE_PTSPINLOCK
        err = pthread_spin_lock(&mutex->lock);
        if(err) return err;
#else
        cpu_spinlock_lock(&mutex->lock);
#endif

        if(mutex->value == __PTHREAD_OBJECT_FREE)
        {
                mutex->value = this;

#if USE_PTSPINLOCK
                (void)pthread_spin_unlock(&mutex->lock);
#else
                cpu_spinlock_unlock(&mutex->lock);
#endif
                return 0;
        }
   
        if(mutex->waiting == 0)
                list_root_init(&mutex->queue);
   
        mutex->waiting += 1;
        tls = cpu_get_tls();
      
        struct __shared_s *shared = (struct __shared_s*)__pthread_tls_get(tls,__PT_TLS_SHARED);
      
        list_add_last(&mutex->queue, &shared->list);
  
#if USE_PTSPINLOCK
        (void)pthread_spin_unlock(&mutex->lock);
#else
        cpu_spinlock_unlock(&mutex->lock);
#endif 
        /* TODO: compute syscall return value (signals treatment) */
        (void)cpu_syscall(NULL, NULL, NULL, NULL, SYS_SLEEP);

        cpu_wbflush();

        return 0;
}

int pthread_mutex_unlock (pthread_mutex_t *mutex)
{
        int err;
        struct __shared_s *next;
        uint_t this;

        int pid = getpid();

        if(mutex == NULL)
                return EINVAL;

        this = (uint_t)pthread_self();

        if((mutex->attr.type == PTHREAD_MUTEX_RECURSIVE) && 
           (mutex->value == this)                        && 
           (mutex->attr.cntr > 0))
        {
                mutex->attr.cntr -= 1;
                return 0;
        }

        if(mutex->attr.scope == PTHREAD_PROCESS_SHARED)
        {
                if(mutex->value != this)
                        err = EPERM;
                else
                        err = sem_post(&mutex->sem);

                return err;
        }

#if USE_PTSPINLOCK 
        err = pthread_spin_lock(&mutex->lock);
        if(err) return err;
#else
        cpu_spinlock_lock(&mutex->lock);
#endif

        if(mutex->value != this)
        {
                (void)pthread_spin_unlock(&mutex->lock);
                return EPERM;
        }

        if(mutex->waiting == 0)
        {
                mutex->value = __PTHREAD_OBJECT_FREE;

#if USE_PTSPINLOCK
                (void)pthread_spin_unlock(&mutex->lock);
#else
                cpu_spinlock_unlock(&mutex->lock);
#endif
                return 0;
        }

#if 0
        if(!(list_empty(&mutex->queue)))
#endif
        {
                next = list_first(&mutex->queue, struct __shared_s, list);
                list_unlink(&next->list);

                mutex->waiting --;
                mutex->value = next->tid;
                cpu_wbflush();

                (void)cpu_syscall((void*)next->tid, NULL, NULL, NULL, SYS_WAKEUP);
        }

#if USE_PTSPINLOCK
        (void)pthread_spin_unlock(&mutex->lock);
#else
        cpu_spinlock_unlock(&mutex->lock);
#endif
        return 0;
}


int pthread_mutex_trylock (pthread_mutex_t *mutex)
{
        int err;
        uint_t this;

        if(mutex == NULL)
                return EINVAL;

        this = (uint_t)pthread_self();

        if((mutex->attr.type == PTHREAD_MUTEX_RECURSIVE) && (mutex->value == this))
        {
                mutex->attr.cntr += 1;
                return 0;
        }

        if(mutex->value == this)
                return EDEADLK;

        if(mutex->attr.scope == PTHREAD_PROCESS_SHARED)
                return sem_trywait(&mutex->sem);

        if(mutex->value != __PTHREAD_OBJECT_FREE)
                return EBUSY;

#if USE_PTSPINLOCK
        err = pthread_spin_lock(&mutex->lock);
        if(err) return err;
#else
        cpu_spinlock_lock(&mutex->lock);
#endif
  
        if(mutex->value != __PTHREAD_OBJECT_FREE)
                err = EBUSY;
        else
                mutex->value = this;
  
#if USE_PTSPINLOCK
        (void)pthread_spin_unlock(&mutex->lock);
#else
        cpu_spinlock_unlock(&mutex->lock);
#endif

        return err;
}


int pthread_mutex_destroy (pthread_mutex_t *mutex)
{
        int err;

        if(mutex == NULL)
                return EINVAL;

        if(mutex->attr.scope == PTHREAD_PROCESS_SHARED)
                return sem_destroy(&mutex->sem);

        print_mutex(mutex);

        if((mutex->waiting != 0) || (mutex->value != __PTHREAD_OBJECT_FREE))
                return EBUSY;
  
        err = pthread_spin_destroy(&mutex->lock);

        if(err) return err;

        mutex->value   = __PTHREAD_OBJECT_DESTROYED;
        mutex->waiting = __PTHREAD_OBJECT_BUSY;
        return 0;
}