source: soft/giet_vm/giet_kernel/ctx_handler.c

//////////////////////////////////////////////////////////////////////////////////
// File     : ctx_handler.c
// Date     : 01/04/2012
// Authors  : alain greiner & joel porquet
// Copyright (c) UPMC-LIP6
//////////////////////////////////////////////////////////////////////////////////

#include <ctx_handler.h>
#include <sys_handler.h>
#include <giet_config.h>
#include <fat32.h>
#include <hard_config.h>
#include <utils.h>
#include <tty0.h>
#include <xcu_driver.h>
#include <bdv_driver.h>

/////////////////////////////////////////////////////////////////////////////////
//     Extern variables and functions
/////////////////////////////////////////////////////////////////////////////////

// defined in giet_kernel/switch.s file
extern void _thread_switch( thread_context_t* , thread_context_t* );

// allocated in boot.c or kernel_init.c files
extern static_scheduler_t* _schedulers[X_SIZE][Y_SIZE][NB_PROCS_MAX];

// allocated in kernel_init.c file
extern fat_desc_t  _fat;

/////////////////////////////////////////////////////////////////////////////////
// This function is called by the _ctx_switch() function.
// It desactivates a thread that received a KILL signal.
// We must release all ressources allocated to the thread
// before the actual desactivation, that set the NORUN_MASK_THREAD
// bit in the thread context.
//////////////////////////////////////////////////////////////////////////////////
static void _ctx_kill_thread( unsigned int x,
                              unsigned int y,
                              unsigned int p,
                              unsigned int ltid )
{
    // get scheduler address
    static_scheduler_t* psched = _schedulers[x][y][p];

    // pretend the thread to kill is the currently scheduled thread
    // (required by the _sys_***_release() calls)
    unsigned int cur_thread = psched->current;
    psched->current = ltid;

    // release BDV lock if taken and reset BDV peripheral
    if ( psched->context[ltid].slot[CTX_LOCKS_ID] & LOCKS_MASK_BDV ) 
    {
        _bdv_set_register( BLOCK_DEVICE_STATUS , 0 );
        _spin_lock_release( &_bdv_lock );
    }

    // release FAT lock if taken 
    if ( psched->context[ltid].slot[CTX_LOCKS_ID] & LOCKS_MASK_FAT ) 
    {
        
        _spin_lock_release( &_fat.fat_lock );
    }

    // release FBF lock if taken 
    if ( psched->context[ltid].slot[CTX_LOCKS_ID] & LOCKS_MASK_FBF ) 
    {
        _sys_fbf_release();
    }

    // release private TTY terminal if required
    if ( psched->context[ltid].slot[CTX_TTY_ID] < NB_TTY_CHANNELS ) 
        _sys_tty_release(); 

    // release private TIM channel if required

    if ( psched->context[ltid].slot[CTX_TIM_ID] < NB_TIM_CHANNELS )
    {
        _sys_tim_release();
    }

    // release private NIC_RX and CMA_RX channels if required
    if ( psched->context[ltid].slot[CTX_NIC_RX_ID] < NB_NIC_CHANNELS )
    {
        _sys_nic_release( 1 );
    }

    // release private NIC_TX and CMA_TX channels if required
    if ( psched->context[ltid].slot[CTX_NIC_TX_ID] < NB_NIC_CHANNELS )
    {
        _sys_nic_release( 0 );
    }

    // release private FBF_CMA channel if required
    if ( psched->context[ltid].slot[CTX_CMA_FB_ID] < NB_CMA_CHANNELS )
    {
        _sys_fbf_cma_release();
    }

    // restore scheduled thread index
    psched->current = cur_thread;

    // set NORUN_MASK_THREAD bit to desactivate the target thread 
    psched->context[ltid].slot[CTX_NORUN_ID] = NORUN_MASK_THREAD;

} // end _ctx_kill_thread()


//////////////////
void _ctx_switch() 
{
    unsigned int gpid       = _get_procid();
    unsigned int cluster_xy = gpid >> P_WIDTH;
    unsigned int x          = cluster_xy >> Y_WIDTH;
    unsigned int y          = cluster_xy & ((1<<Y_WIDTH)-1);
    unsigned int p          = gpid & ((1<<P_WIDTH)-1);

    unsigned int ltid;     // index for loops on threads in scheduler

    // get calling thread scheduler address
    static_scheduler_t* psched = (static_scheduler_t*)_get_sched();

    // get number of threads allocated to scheduler
    unsigned int threads = psched->threads;

    // get current thread ltid
    unsigned int curr_thread_id = psched->current;

    // first loop on threads: handle all pending KILL signals
    for ( ltid = 0 ; ltid < threads ; ltid++ )
    {
        if ( psched->context[ltid].slot[CTX_SIGS_ID] & SIGS_MASK_KILL )
        {
            // acknowledge KILL signal
            _atomic_and( &psched->context[ltid].slot[CTX_SIGS_ID], ~SIGS_MASK_KILL );

            // desactivate the killed thread
            _ctx_kill_thread( x , y , p , ltid );
        }
    }

    // second loop: select next thread using a round-robin policy
    unsigned int next_thread_id;
    unsigned int found = 0;
    for ( ltid = curr_thread_id + 1 ; ltid < (curr_thread_id + 1 + threads) ; ltid++ ) 
    {
        next_thread_id = ltid % threads;

        // test if the thread is runable
        if ( psched->context[next_thread_id].slot[CTX_NORUN_ID] == 0 )
        {
            found = 1;
            break;
        }
    }

    // launch idle_thread if no runable thread
    if ( found == 0 ) next_thread_id = IDLE_THREAD_INDEX;

    if ( curr_thread_id != next_thread_id )  // actual thread switch required
    {

#if GIET_DEBUG_SWITCH 
unsigned int x = cluster_xy >> Y_WIDTH;
unsigned int y = cluster_xy & ((1<<Y_WIDTH)-1);
if ( (_get_proctime() > GIET_DEBUG_SWITCH) && (x == 0) && (y == 0) && (p == 0) )
_printf("\n[DEBUG SWITCH] (%d) -> (%d) on processor[%d,%d,%d] at cycle %d\n",
        curr_thread_id, next_thread_id, x, y , p, _get_proctime() );
#endif

        thread_context_t* curr_ctx_vaddr = &(psched->context[curr_thread_id]);
        thread_context_t* next_ctx_vaddr = &(psched->context[next_thread_id]);

        // reset TICK timer counter. 
        _xcu_timer_reset_cpt( cluster_xy, p );

        // set current thread index 
        psched->current = next_thread_id;

        // makes context switch
        _thread_switch( curr_ctx_vaddr , next_ctx_vaddr );

        // only modify the PTPR when necessary, in order to avoid unnecessary
        // TLBs flush.
        if (curr_ctx_vaddr->slot[CTX_PTPR_ID] !=
            next_ctx_vaddr->slot[CTX_PTPR_ID])
        {
            _set_mmu_ptpr(next_ctx_vaddr->slot[CTX_PTPR_ID]);
        }
    }
} //end _ctx_switch()


///////////////////
void _idle_thread() 
{
    unsigned int gpid       = _get_procid();
    unsigned int cluster_xy = gpid >> P_WIDTH;
    unsigned int x          = cluster_xy >> Y_WIDTH;
    unsigned int y          = cluster_xy & ((1<<Y_WIDTH)-1);
    unsigned int p          = gpid & ((1<<P_WIDTH)-1);

    while(1)
    {
        _sleep( GIET_IDLE_THREAD_PERIOD );

        // warning message
        _printf("\n[GIET WARNING] Processor[%d,%d,%d] still idle at cycle %u",
                x , y , p , _get_proctime() );
    }
} // end ctx_idle()


////////////////
void _ctx_eret() 
{
    asm volatile("eret");
}


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