sched.cxx

ecos实时嵌入式操作系统

//==========================================================================
//
//      sched/sched.cxx
//
//      Scheduler class implementations
//
//==========================================================================
//####ECOSGPLCOPYRIGHTBEGIN####
// -------------------------------------------
// This file is part of eCos, the Embedded Configurable Operating System.
// Copyright (C) 1998, 1999, 2000, 2001, 2002 Red Hat, Inc.
//
// eCos is free software; you can redistribute it and/or modify it under
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//
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// 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 eCos; if not, write to the Free Software Foundation, Inc.,
// 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
//
// As a special exception, if other files instantiate templates or use macros
// or inline functions from this file, or you compile this file and link it
// with other works to produce a work based on this file, this file does not
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//
// Alternative licenses for eCos may be arranged by contacting Red Hat, Inc.
// at http://sources.redhat.com/ecos/ecos-license/
// -------------------------------------------
//####ECOSGPLCOPYRIGHTEND####
//==========================================================================
//#####DESCRIPTIONBEGIN####
//
// Author(s):   nickg
// Contributors:        nickg
// Date:        1997-09-15
// Purpose:     Scheduler class implementation
// Description: This file contains the definitions of the scheduler class
//              member functions that are common to all scheduler
//              implementations.
//
//####DESCRIPTIONEND####
//
//==========================================================================

#include <pkgconf/kernel.h>

#include <cyg/kernel/ktypes.h>         // base kernel types
#include <cyg/infra/cyg_trac.h>        // tracing macros
#include <cyg/infra/cyg_ass.h>         // assertion macros
#include <cyg/kernel/instrmnt.h>       // instrumentation

#include <cyg/kernel/sched.hxx>        // our header

#include <cyg/kernel/thread.hxx>       // thread classes
#include <cyg/kernel/intr.hxx>         // Interrupt interface

#include <cyg/hal/hal_arch.h>          // Architecture specific definitions

#include <cyg/kernel/thread.inl>       // thread inlines
#include <cyg/kernel/sched.inl>        // scheduler inlines

//-------------------------------------------------------------------------
// Some local tracing control - a default.
#ifdef CYGDBG_USE_TRACING
# if !defined( CYGDBG_INFRA_DEBUG_TRACE_ASSERT_SIMPLE ) && \
     !defined( CYGDBG_INFRA_DEBUG_TRACE_ASSERT_FANCY  )
   // ie. not a tracing implementation that takes a long time to output

#  ifndef CYGDBG_KERNEL_TRACE_UNLOCK_INNER
#   define CYGDBG_KERNEL_TRACE_UNLOCK_INNER
#  endif // control not already defined

# endif  // trace implementation not ..._SIMPLE && not ..._FANCY
#endif   // CYGDBG_USE_TRACING

// -------------------------------------------------------------------------
// Static Cyg_Scheduler class members

// We start with sched_lock at 1 so that any kernel code we
// call during initialization will not try to reschedule.

CYGIMP_KERNEL_SCHED_LOCK_DEFINITIONS;

Cyg_Thread              *volatile Cyg_Scheduler_Base::current_thread[CYGNUM_KERNEL_CPU_MAX];

volatile cyg_bool       Cyg_Scheduler_Base::need_reschedule[CYGNUM_KERNEL_CPU_MAX];

Cyg_Scheduler           Cyg_Scheduler::scheduler CYG_INIT_PRIORITY( SCHEDULER );

volatile cyg_ucount32   Cyg_Scheduler_Base::thread_switches[CYGNUM_KERNEL_CPU_MAX];

#ifdef CYGPKG_KERNEL_SMP_SUPPORT

CYG_BYTE cyg_sched_cpu_interrupt[CYGNUM_KERNEL_CPU_MAX][sizeof(Cyg_Interrupt)]
                                 CYGBLD_ANNOTATE_VARIABLE_SCHED;

__externC cyg_ISR cyg_hal_cpu_message_isr;
__externC cyg_DSR cyg_hal_cpu_message_dsr;

inline void *operator new(size_t size, void *ptr) { return ptr; };

#endif

// -------------------------------------------------------------------------
// Scheduler unlock function.

// This is only called when there is the potential for real work to be
// done. Other cases are handled in Cyg_Scheduler::unlock() which is
// an inline; _or_ this function may have been called from
// Cyg_Scheduler::reschedule(), or Cyg_Scheduler::unlock_reschedule. The
// new_lock argument contains the value that the scheduler lock should
// have after this function has completed. If it is zero then the lock is
// being released and some extra work (running ASRs, checking for DSRs) is
// done before returning. If it is non-zero then it must equal the
// current value of the lock, and is used to indicate that we want to
// reacquire the scheduler lock before returning. This latter option
// only makes any sense if the current thread is no longer runnable,
// e.g. sleeping, otherwise this function will do nothing.
// This approach of passing in the lock value at the end effectively
// makes the scheduler lock a form of per-thread variable. Each call
// to unlock_inner() carries with it the value the scheduler should
// have when it reschedules this thread back, and leaves this function.
// When it is non-zero, and the thread is rescheduled, no ASRS are run,
// or DSRs processed. By doing this, it makes it possible for threads
// that want to go to sleep to wake up with the scheduler lock in the
// same state it was in before.

void Cyg_Scheduler::unlock_inner( cyg_ucount32 new_lock )
{
#ifdef CYGDBG_KERNEL_TRACE_UNLOCK_INNER
    CYG_REPORT_FUNCTION();
#endif    

    do {

        CYG_PRECONDITION( new_lock==0 ? get_sched_lock() == 1 :
                          ((get_sched_lock() == new_lock) || (get_sched_lock() == new_lock+1)),
                          "sched_lock not at expected value" );
        
#ifdef CYGIMP_KERNEL_INTERRUPTS_DSRS
        
        // Call any pending DSRs. Do this here to ensure that any
        // threads that get awakened are properly scheduled.

        if( new_lock == 0 && Cyg_Interrupt::DSRs_pending() )
            Cyg_Interrupt::call_pending_DSRs();
#endif

        Cyg_Thread *current = get_current_thread();

        CYG_ASSERTCLASS( current, "Bad current thread" );

#ifdef CYGFUN_KERNEL_ALL_THREADS_STACK_CHECKING
        // should have  CYGVAR_KERNEL_THREADS_LIST
        current = Cyg_Thread::get_list_head();
        while ( current ) {
            current->check_stack();
            current = current->get_list_next();
        }
        current = get_current_thread();
#endif

#ifdef CYGFUN_KERNEL_THREADS_STACK_CHECKING
        current->check_stack();
#endif

        // If the current thread is going to sleep, or someone
        // wants a reschedule, choose another thread to run

        if( current->state != Cyg_Thread::RUNNING || get_need_reschedule() ) {

            CYG_INSTRUMENT_SCHED(RESCHEDULE,0,0);
            
            // Get the next thread to run from scheduler
            Cyg_Thread *next = scheduler.schedule();

            CYG_CHECK_DATA_PTR( next, "Invalid next thread pointer");
            CYG_ASSERTCLASS( next, "Bad next thread" );

            if( current != next )
            {

                CYG_INSTRUMENT_THREAD(SWITCH,current,next);

                // Count this thread switch
                thread_switches[CYG_KERNEL_CPU_THIS()]++;

#ifdef CYGFUN_KERNEL_THREADS_STACK_CHECKING
                next->check_stack(); // before running it
#endif

                // Switch contexts
                HAL_THREAD_SWITCH_CONTEXT( &current->stack_ptr,
                                           &next->stack_ptr );

                // Worry here about possible compiler
                // optimizations across the above call that may try to
                // propogate common subexpresions.  We would end up
                // with the expression from one thread in its
                // successor. This is only a worry if we do not save
                // and restore the complete register set. We need a
                // way of marking functions that return into a
                // different context. A temporary fix would be to
                // disable CSE (-fdisable-cse) in the compiler.
                
                // We return here only when the current thread is
                // rescheduled.  There is a bit of housekeeping to do
                // here before we are allowed to go on our way.

                CYG_CHECK_DATA_PTR( current, "Invalid current thread pointer");
                CYG_ASSERTCLASS( current, "Bad current thread" );

                current_thread[CYG_KERNEL_CPU_THIS()] = current;   // restore current thread pointer
            }

#ifdef CYGSEM_KERNEL_SCHED_TIMESLICE
            // Reset the timeslice counter so that this thread gets a full
            // quantum. 
            reset_timeslice_count();
#endif

            clear_need_reschedule();    // finished rescheduling
        }

        if( new_lock == 0 )
        {

#ifdef CYGSEM_KERNEL_SCHED_ASR_SUPPORT

            // Check whether the ASR is pending and not inhibited.  If
            // we can call it, then transfer this info to a local
            // variable (call_asr) and clear the pending flag.  Note
            // that we only do this if the scheduler lock is about to
            // be zeroed. In any other circumstance we are not
            // unlocking.

            cyg_bool call_asr = false;
            
            if( (current->asr_inhibit == 0) && current->asr_pending )
            {
                call_asr = true;
                current->asr_pending = false;
            }
#endif
            
            HAL_REORDER_BARRIER(); // Make sure everything above has happened
                                   // by this point
            zero_sched_lock();     // Clear the lock
            HAL_REORDER_BARRIER();
                
#ifdef CYGIMP_KERNEL_INTERRUPTS_DSRS

            // Now check whether any DSRs got posted during the thread
            // switch and if so, go around again. Making this test after
            // the lock has been zeroed avoids a race condition in which
            // a DSR could have been posted during a reschedule, but would
            // not be run until the _next_ time we release the sched lock.

            if( Cyg_Interrupt::DSRs_pending() ) {
                inc_sched_lock();   // reclaim the lock
                continue;           // go back to head of loop
            }

#endif
            // Otherwise the lock is zero, we can return.

//            CYG_POSTCONDITION( get_sched_lock() == 0, "sched_lock not zero" );

#ifdef CYGSEM_KERNEL_SCHED_ASR_SUPPORT
            // If the test within the sched_lock indicating that the ASR
            // be called was true, call it here. Calling the ASR must be
            // the very last thing we do here, since it must run as close
            // to "user" state as possible.
        
            if( call_asr ) current->asr(current->asr_data);
#endif

        }
        else
        {
            // If new_lock is non-zero then we restore the sched_lock to
            // the value given.
            
            HAL_REORDER_BARRIER();
            
            set_sched_lock(new_lock);
            
            HAL_REORDER_BARRIER();            
        }
        
#ifdef CYGDBG_KERNEL_TRACE_UNLOCK_INNER
        CYG_REPORT_RETURN();
#endif
        return;

    } while( 1 );

    CYG_FAIL( "Should not be executed" );
}

// -------------------------------------------------------------------------
// Start the scheduler. This is called after the initial threads have been
// created to start scheduling. It gets any other CPUs running, and then
// enters the scheduler.

void Cyg_Scheduler::start()
{
    CYG_REPORT_FUNCTION();

#ifdef CYGPKG_KERNEL_SMP_SUPPORT

    HAL_SMP_CPU_TYPE cpu;
    
    for( cpu = 0; cpu < CYG_KERNEL_CPU_COUNT(); cpu++ )
    {
        // Don't start this CPU, it is running already!
        if( cpu == CYG_KERNEL_CPU_THIS() )
            continue;

        CYG_KERNEL_CPU_START( cpu );
    }

#endif    
    
    start_cpu();
}

// -------------------------------------------------------------------------
// Start scheduling on this CPU. This is called on each CPU in the system
// when it is started.

void Cyg_Scheduler::start_cpu()
{
    CYG_REPORT_FUNCTION();

#ifdef CYGPKG_KERNEL_SMP_SUPPORT

    // Set up the inter-CPU interrupt for this CPU

    Cyg_Interrupt * intr = new( (void *)&cyg_sched_cpu_interrupt[HAL_SMP_CPU_THIS()] )
        Cyg_Interrupt( CYGNUM_HAL_SMP_CPU_INTERRUPT_VECTOR( HAL_SMP_CPU_THIS() ),
                       0,
                       0,
                       cyg_hal_cpu_message_isr,
                       cyg_hal_cpu_message_dsr
                     );

    intr->set_cpu( intr->get_vector(), HAL_SMP_CPU_THIS() );
    
    intr->attach();

    intr->unmask_interrupt( intr->get_vector() );
    
#endif    
    
    // Get the first thread to run from scheduler
    register Cyg_Thread *next = scheduler.schedule();

    CYG_ASSERTCLASS( next, "Bad initial thread" );

    clear_need_reschedule();            // finished rescheduling