/*
 * scheduler.c - Core scheduler implementation.
 * 
 * Author    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 <kernel_config.h>
#include <hal_types.h>
#include <hal_irqmask.h>
#include <hal_context.h>
#include <printk.h>
#include <list.h>
#include <core.h>
#include <thread.h>
#include <scheduler.h>


////////////////////////////////
void sched_init( core_t * core )
{
    scheduler_t * sched = &core->scheduler;

    sched->u_threads_nr   = 0;
    sched->k_threads_nr   = 0;

    sched->current        = NULL;
    sched->idle           = NULL;
    sched->u_last         = NULL;
    sched->k_last         = NULL;

    // initialise threads lists
    list_root_init( &sched->u_root );
    list_root_init( &sched->k_root );

}  // end sched_init()

////////////////////////////////////////////
void sched_register_thread( core_t   * core,
                            thread_t * thread )
{
    scheduler_t * sched = &core->scheduler;
    thread_type_t type  = thread->type;

    // take lock protecting sheduler lists
    spinlock_lock( &sched->lock );

    // register thread
    if( type == THREAD_USER )
    {
        list_add_last( &sched->u_root , &thread->sched_list );
        sched->u_threads_nr++;
    }
    else // kernel thread
    {
        list_add_last( &sched->k_root , &thread->sched_list );
        sched->k_threads_nr++;
    }

    // release lock 
    spinlock_unlock( &sched->lock );

}  // end sched_register()

/////////////////////////////////////////////
void sched_remove_thread( thread_t * thread )
{
    core_t       * core  = thread->core;
    scheduler_t  * sched = &core->scheduler;
    thread_type_t  type  = thread->type;

    // take lock protecting sheduler lists
    spinlock_lock( &sched->lock );

    // remove thread
    if( type == THREAD_USER )
    {
        list_unlink( &thread->sched_list );
        sched->u_threads_nr--;
    }
    else // kernel thread 
    {
        list_unlink( &thread->sched_list );
        sched->k_threads_nr--;
    }

    // release lock
    spinlock_unlock( &sched->lock );

}  // end sched_remove()

///////////////////////////////////////////
void sched_kill_thread( thread_t * thread )
{
    // check thread locks
    if( thread_can_yield() == false )
    {
        printk("\n[PANIC] in %s : thread %x in process %x on core[%x][%d]"
               " did not released all locks\n",
               __FUNCTION__ , thread->trdid , thread->process->pid, 
               local_cxy , thread->core->lid ); 
        hal_core_sleep();
    }

    // remove thread from scheduler
    sched_remove_thread( thread );

    // reset the THREAD_SIG_KILL signal
    thread_reset_signal( thread , THREAD_SIG_KILL );

}  // end sched_kill_thread()

////////////////////////////////////////
thread_t * sched_select( core_t * core )
{
    thread_t * thread;

    scheduler_t * sched = &core->scheduler;

    // take lock protecting sheduler lists
    spinlock_lock( &sched->lock );

    list_entry_t * current;
    list_entry_t * last;

    // first scan the kernel threads
    last    = sched->k_last;
    current = sched->k_last;
    do
    {
        // get next entry in kernel list
        current = list_next( &sched->k_root , current );

        // skip the list root that does not contain a thread
        if( current == NULL ) continue;

        // get thread pointer
        thread = LIST_ELEMENT( current , thread_t , sched_list );

        // return thread if not blocked
        if( thread->blocked == 0 ) 
        {
            // release lock 
            spinlock_unlock( &sched->lock );
            return thread;
        }
    }
    while( current != last );

    // second scan the user threads
    last    = sched->u_last;
    current = sched->u_last;
    do
    {
        // get next entry in user list
        current = list_next( &sched->u_root , current );

        // skip the list root that does not contain a thread
        if( current == NULL ) continue;

        // get thread pointer
        thread = LIST_ELEMENT( current , thread_t , sched_list );

        // return thread if not blocked
        if( thread->blocked == 0 )
        {
            // release lock 
            spinlock_unlock( &sched->lock );
            return thread;
        }
    }
    while( current != last );

    // release lock 
    spinlock_unlock( &sched->lock );

    // third, return idle thread if no runnable thread
    return sched->idle;

}  // end sched_elect()

//////////////////////////////////////////
void sched_handle_signals( core_t * core )
{
    list_entry_t * iter;
    thread_t     * thread;

    scheduler_t  * sched = &core->scheduler;

    // take lock protecting threads lists
    spinlock_lock( &sched->lock );

    // handle user threads
    LIST_FOREACH( &sched->u_root , iter )
    {
        thread = LIST_ELEMENT( iter , thread_t , sched_list );
        if( thread->signals & THREAD_SIG_KILL )  sched_kill_thread( thread );
    }

    // handle kernel threads
    LIST_FOREACH( &sched->k_root , iter )
    {
        thread = LIST_ELEMENT( iter , thread_t , sched_list );
        if( thread->signals & THREAD_SIG_KILL )  sched_kill_thread( thread );
    }

    // release lock 
    spinlock_unlock( &sched->lock );

} // end sched_handle_signals()

//////////////////
void sched_yield()
{
    reg_t         sr_save;
    thread_t    * next;

    thread_t    * current = CURRENT_THREAD;
    core_t      * core    = current->core;

    if( thread_can_yield() == false )
    {
        printk("\n[PANIC] in %s : thread %x for process %x on core_gid %x"
               " has not released all locks at cycle %d\n",
               __FUNCTION__, current->trdid, current->process->pid, 
               local_cxy , core->lid , hal_time_stamp() );
        hal_core_sleep();
    }

    // desactivate IRQs
    hal_disable_irq( &sr_save );

    // first loop on all threads to handle pending signals
    sched_handle_signals( core );

    // second loop on threads to select next thread
    next = sched_select( core );

    // check stack overflow for selected thread
    if( next->signature != THREAD_SIGNATURE )
    {
        printk("\n[PANIC] in %s : detected stack overflow for thread %x of process %x"
               " on core [%x][%d]\n",
               __FUNCTION__, next->trdid, next->process->pid, local_cxy , core->lid );
        hal_core_sleep();
	}
	
	sched_dmsg("\n[INFO] %s on core %d in cluster %x / old thread = %x / new thread = %x\n",
               __FUNCTION__, core->lid, local_cxy, current->trdid, next->trdid );

    // switch contexts if new thread
	if( next != current )  
	{
        hal_cpu_context_save( current );
        hal_cpu_context_restore( next );
	}

    // restore IRQs
    hal_restore_irq( sr_save );

	if( current->type != THREAD_USER ) return;

	if( current == core->fpu_owner )  hal_fpu_enable();
	else                              hal_fpu_disable();

}  // end sched_yield()

//////////////////////////////////////
void sched_switch_to( thread_t * new )
{
    reg_t         sr_save;

    thread_t    * current = CURRENT_THREAD;
    core_t      * core    = current->core;
    process_t   * process = current->process;

    // check calling thread released all locks
    if( thread_can_yield() == false )
    {
        printk("\n[PANIC] in %s : thread %x for process %x on core %d in cluster %x"
               " has not released all locks\n",
               __FUNCTION__, current->trdid, process->pid, core->lid, local_cxy );
        hal_core_sleep();
    }

    // check new thread attached to same core as the calling thread
    if( new->core != current->core )
    {
        printk("\n[PANIC] in %s : new thread %x is attached to core %d"
               " different from core %d of current thread\n",
               __FUNCTION__, new->trdid, new->core->lid, core->lid , current->trdid );
        hal_core_sleep();
    }

    // check new thread not blocked
    if( new->blocked == 0 )
    {
        printk("\n[PANIC] in %s for thread %x of process %x on core %d in cluster %x"
               " : new thread %x is blocked\n",
               __FUNCTION__, current->trdid, process->pid , core->lid, local_cxy , new->trdid );
        hal_core_sleep();
    }

    // check stack overflow for new thread
    if( new->signature != THREAD_SIGNATURE )
    {
        printk("\n[PANIC] in %s : stack overflow for new thread %x of process %x"
               " on core %d in cluster %x\n",
               __FUNCTION__, new->trdid, process->pid , core->lid , local_cxy );
        hal_core_sleep();
	}

    // desactivate IRQs
    hal_disable_irq( &sr_save );

    // loop on all threads to handle pending signals
    sched_handle_signals( core );

    // check stack overflow for new thread
    if( new->signature != THREAD_SIGNATURE )
    {
        printk("PANIC %s detected stack overflow for thread %x of process %x"
               " on core %d in cluster %x\n",
               __FUNCTION__, new->trdid, new->process->pid, core->lid, local_cxy);
        hal_core_sleep();
	}
	
	sched_dmsg("INFO : %s on core %d in cluster %x / old thread = %x / new thread = %x\n",
               __FUNCTION__, core->lid, local_cxy, current->trdid, new->trdid );

    // switch contexts if new thread
    hal_cpu_context_save( current );
    hal_cpu_context_restore( new );

    // restore IRQs
    hal_restore_irq( sr_save );

	if( current->type != THREAD_USER ) return;

	if( current == core->fpu_owner )  hal_fpu_enable();
	else                              hal_fpu_disable();

}  // end sched_switch_to()