source: trunk/kernel/libk/remote_spinlock.c @ 8

/*
 * remote_spinlock.c - kernel remote spinlock implementation.
 * 
 * Authors  Mohamed Karaoui (2015)
 *          Alain   Greiner (2016)
 *
 * Copyright (c) UPMC Sorbonne Universites
 *
 * This file is part of ALMOS-MKH.
 *
 * ALMOS-MKH 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-MKH 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-MKH; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <hal_types.h>
#include <hal_remote.h>
#include <hal_irqmask.h>
#include <thread.h>
#include <cluster.h>
#include <scheduler.h>
#include <remote_spinlock.h>

////////////////////////////////////////
void remote_spinlock_init( xptr_t lock )
{ 
    remote_spinlock_t * ptr = (remote_spinlock_t *)GET_PTR( lock );
    cxy_t               cxy = GET_CXY( lock );

    hal_remote_sw ( XPTR( cxy , &ptr->taken ) , 0 );
    hal_remote_swd( XPTR( cxy , &ptr->owner ) , XPTR_NULL );
    xlist_entry_init( XPTR( cxy , &ptr->list ) ); 
}

///////////////////////////////////////////////
uint32_t remote_spinlock_trylock( xptr_t lock )
{ 
        uint32_t            mode;
        bool_t              isAtomic = false;

    // get cluster and local pointer on remote_spinlock
    remote_spinlock_t * lock_ptr = (remote_spinlock_t *)GET_PTR( lock );
    cxy_t               lock_cxy = GET_CXY( lock );

    // get cluster and local pointer on local thread
    cxy_t               thread_cxy = local_cxy;
    thread_t          * thread_ptr = CURRENT_THREAD;

    // disable interrupts
    hal_disable_irq( &mode );

        if( hal_remote_lw( XPTR( lock_cxy , &lock_ptr->taken ) ) == 0 )
    {
                isAtomic = hal_remote_atomic_cas( XPTR( lock_cxy , &lock_ptr->taken ) , 0 , 1 );
    }

        if( isAtomic == false )    // failure 
        {
                hal_restore_irq( mode );
                return 1;
        }
    else                      // success : register lock in thread
    {
            thread_ptr->remote_locks++;

        hal_remote_swd( XPTR( lock_cxy , &lock_ptr->owner ) ,
                    (uint64_t)XPTR( thread_cxy , thread_ptr) );

        xlist_add_first( XPTR( thread_cxy , &thread_ptr->xlocks_root ) ,
                     XPTR( lock_cxy , &lock_ptr->list ) );

            hal_restore_irq(mode);  
            return 0;
    }
}

////////////////////////////////////////
void remote_spinlock_lock( xptr_t lock )
{
    bool_t              isAtomic = false;
        uint32_t            mode;
    volatile uint32_t   taken;

    // get cluster and local pointer on remote_spinlock
    remote_spinlock_t * lock_ptr = (remote_spinlock_t *)GET_PTR( lock );
    cxy_t               lock_cxy = GET_CXY( lock );

    // get cluster and local pointer on local thread
    cxy_t               thread_cxy = local_cxy;
    thread_t          * thread_ptr = CURRENT_THREAD;

    // disable interrupts
        hal_disable_irq( &mode );
  
    // loop until success 
        while( isAtomic == false )
        {
                taken = hal_remote_lw( XPTR( lock_cxy , &lock_ptr->taken ) );

        // deschedule if possible when lock already taken
                if( taken != 0 )
                {
                hal_restore_irq( mode );
            if( thread_can_yield() ) sched_yield();
                hal_disable_irq( &mode );
                        continue;
                }
    
        // try to take the lock if not already taken
                isAtomic = hal_remote_atomic_cas( XPTR( lock_cxy , &lock_ptr->taken ) , 0 , 1 );
        }

    // register lock in thread
        thread_ptr->remote_locks++;

    hal_remote_swd( XPTR( lock_cxy , &lock_ptr->owner ) ,
                    (uint64_t)XPTR( thread_cxy , thread_ptr) );

    xlist_add_first( XPTR( thread_cxy , &thread_ptr->xlocks_root ) ,
                     XPTR( lock_cxy , &lock_ptr->list ) );

    // enable interrupts
        hal_restore_irq( mode );
}

//////////////////////////////////////////
void remote_spinlock_unlock( xptr_t lock )
{
    // get cluster and local pointer on remote_spinlock
    remote_spinlock_t * lock_ptr = (remote_spinlock_t *)GET_PTR( lock );
    cxy_t               lock_cxy = GET_CXY( lock );

    // get pointer on local thread
    thread_t          * thread_ptr = CURRENT_THREAD;

        hal_remote_swd( XPTR( lock_cxy , &lock_ptr->owner ) , XPTR_NULL );

        hal_remote_sw ( XPTR( lock_cxy , &lock_ptr->taken ) , 0 );

        thread_ptr->remote_locks--;

    xlist_unlink( XPTR( lock_cxy , &lock_ptr->list ) );
}