source: trunk/sys/libpthread/pthread_spinlock.c @ 67

/*
 * pthread_spinlock.c - pthread spinlock 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 <cpu-syscall.h>
#include <pthread.h>

#include <stdio.h>

#undef dmsg_r
#define dmsg_r(...)


int pthread_spin_init (pthread_spinlock_t *lock, int pshared)
{
        if (lock == NULL)
                return EINVAL;
  
        lock->val = __PTHREAD_OBJECT_FREE;

        return 0;
}

#include <unistd.h>

int pthread_spin_lock (pthread_spinlock_t *lock)
{
        volatile uint_t cntr;
        register bool_t isAtomic;
        register uint_t this;
        register uint_t limit;
        
        if (lock == NULL)
        {
                dmsg_r(stderr, "%s: pid %d, tid %d, EINVAL\n", 
                       __FUNCTION__, (int)getpid(), (unsigned)pthread_self);

                return EINVAL;
        }

        this = (uint_t)pthread_self();

        cpu_invalid_dcache_line(lock);

        // Check if lock is not owned by the caller thread.
        if (lock->val == this)
        {
                dmsg_r(stderr, "%s: pid %d, tid %d, 0x%x EDEADLK\n", 
                       __FUNCTION__, (int)getpid(), (unsigned)pthread_self(), (unsigned)lock);

                return EDEADLK;
        }

        cntr = 0;
        limit = 10000;

        // Take the lock
        while((isAtomic = cpu_atomic_cas(&lock->val, __PTHREAD_OBJECT_FREE, (sint_t)this)) == false)
        {
                cntr ++;
                if(cntr > limit)
                {
                        pthread_yield();

                        dmsg_r(stderr, "%s: pid %d, tid %d, val %d, 0x%x, yielded\n", 
                               __FUNCTION__, (int)getpid(), (unsigned)this, (unsigned)lock->val, (unsigned)lock);

                        cpu_invalid_dcache_line(lock);
                        limit = 2000;
                        cntr  = 0;
                }
        }

        dmsg_r(stderr, "%s: pid %d, tid %d, 0x%x locked\n", 
               __FUNCTION__, (int)getpid(), (unsigned)pthread_self(), (unsigned)lock);

        return 0;
}

int pthread_spin_trylock(pthread_spinlock_t *lock)
{
        register bool_t isAtomic;
        register uint_t this;

        if(lock == NULL)
                return EINVAL;

        this = (uint_t)pthread_self();
        cpu_invalid_dcache_line(lock);

        // Check if lock is not owned by the caller thread.
        if (lock->val == this)
                return EDEADLK;

        isAtomic = cpu_atomic_cas(&lock->val, __PTHREAD_OBJECT_FREE, (sint_t)this);
   
        if(isAtomic == false)
        {
                cpu_invalid_dcache_line(lock);
                return EBUSY;
        }

        return 0;
}

int pthread_spin_unlock (pthread_spinlock_t *lock)
{
        if (lock == NULL)
        {
                dmsg_r(stderr, "%s: pid %d, tid %d EINVAL\n", 
                       __FUNCTION__, (int)getpid(), (unsigned)pthread_self());
                return EINVAL;
        }

        // Check if lock is busy and owned by the caller thread.
        if (lock->val != pthread_self())
        {
                dmsg_r(stderr, "libpthread: %s: pid %d, tid %d, val %d, EPERM\n",
                       __FUNCTION__, (int)getpid(), (int)pthread_self(), (int)lock->val);
                
                return EPERM;
        }
        // Update lock's control informations  
        lock->val = __PTHREAD_OBJECT_FREE;
        cpu_wbflush();
        cpu_invalid_dcache_line(lock);

        dmsg_r(stderr, "%s: pid %d, tid %d, 0x%x unlocked\n", 
               __FUNCTION__, (int)getpid(), (unsigned)pthread_self(), (unsigned)lock);

        return 0;
}

int pthread_spin_destroy (pthread_spinlock_t *lock)
{
        if (lock == NULL)
                return EINVAL;

        // Check if lock is not occupied by a thread.
        // If lock is occupied, then return immediately with EBUSY error code.
        if(lock->val != __PTHREAD_OBJECT_FREE)
                return EBUSY;

        // Update lock's control informations.
        lock->val = __PTHREAD_OBJECT_DESTROYED;
        cpu_invalid_dcache_line(lock);
        cpu_wbflush();
        return 0;
}