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[/] [openrisc/] [trunk/] [rtos/] [ecos-3.0/] [packages/] [kernel/] [current/] [src/] [sync/] [cnt_sem2.cxx] - Rev 851
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//========================================================================== // // sync/cnt_sem2.cxx // // Counting semaphore implementation // //========================================================================== // ####ECOSGPLCOPYRIGHTBEGIN#### // ------------------------------------------- // This file is part of eCos, the Embedded Configurable Operating System. // Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc. // // eCos 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; either version 2 or (at your option) any later // version. // // eCos 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 eCos; if not, write to the Free Software Foundation, Inc., // 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, 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 by itself cause the resulting work to be covered by // the GNU General Public License. However the source code for this file // must still be made available in accordance with section (3) of the GNU // General Public License v2. // // This exception does not invalidate any other reasons why a work based // on this file might be covered by the GNU General Public License. // ------------------------------------------- // ####ECOSGPLCOPYRIGHTEND#### //========================================================================== //#####DESCRIPTIONBEGIN#### // // Author(s): nickg // Contributors: nickg // Date: 1997-09-24 // Purpose: Cyg_Counting_Semaphore implementation // Description: This file contains the implementations of the counting semaphore // class. // //####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/thread.inl> // Cyg_Thread inlines #include <cyg/kernel/sema2.hxx> // our header #include <cyg/kernel/sched.inl> // scheduler inlines // ------------------------------------------------------------------------- // Constructor Cyg_Counting_Semaphore2::Cyg_Counting_Semaphore2( cyg_count32 init_count // Initial count value ) { count = init_count; } // ------------------------------------------------------------------------- // Destructor Cyg_Counting_Semaphore2::~Cyg_Counting_Semaphore2() { CYG_REPORT_FUNCTION(); #if 0 CYG_ASSERT( queue.empty(), "Destroying semaphore with waiting threads"); #endif // Prevent preemption Cyg_Scheduler::lock(); while ( ! queue.empty() ) { Cyg_Thread *thread = queue.dequeue(); thread->set_wake_reason( Cyg_Thread::DESTRUCT ); thread->wake(); } // Unlock the scheduler and maybe switch threads Cyg_Scheduler::unlock(); CYG_REPORT_RETURN(); } // ------------------------------------------------------------------------- // Wait until the count can be decremented without it becoming // negative. cyg_bool Cyg_Counting_Semaphore2::wait() { CYG_REPORT_FUNCTION(); Cyg_Thread *self = Cyg_Thread::self(); cyg_bool result = true; // Prevent preemption Cyg_Scheduler::lock(); CYG_INSTRUMENT_CNTSEM( CLAIM, this, count ); if ( 0 < count ) { count--; Cyg_Scheduler::unlock(); } else { self->set_sleep_reason( Cyg_Thread::WAIT ); self->sleep(); queue.enqueue( self ); CYG_INSTRUMENT_CNTSEM( WAIT, this, 0 ); Cyg_Scheduler::unlock(); CYG_INSTRUMENT_CNTSEM( WOKE, this, count ); switch( self->get_wake_reason() ) { case Cyg_Thread::DESTRUCT: case Cyg_Thread::BREAK: result = false; break; case Cyg_Thread::EXIT: self->exit(); break; default: break; } } CYG_REPORT_RETVAL( result ); return result; } // ------------------------------------------------------------------------- // Wait until the count can be decremented without it becoming // negative. #ifdef CYGFUN_KERNEL_THREADS_TIMER cyg_bool Cyg_Counting_Semaphore2::wait( cyg_tick_count abs_timeout ) { CYG_REPORT_FUNCTION(); Cyg_Thread *self = Cyg_Thread::self(); cyg_bool result = true; // Prevent preemption Cyg_Scheduler::lock(); CYG_INSTRUMENT_CNTSEM( CLAIM, this, count ); if ( 0 < count ) { count--; Cyg_Scheduler::unlock(); } else { // Put thread in sleep state before setting timer since if the // timeout is in the past, it will be re-awoken // immediately. If this happens then wake_reason will not be // NONE. self->sleep(); self->set_timer( abs_timeout, Cyg_Thread::TIMEOUT ); // only enqueue if the timeout did not already happen if( Cyg_Thread::NONE == self->get_wake_reason() ) queue.enqueue( self ); CYG_INSTRUMENT_CNTSEM( WAIT, this, 0 ); Cyg_Scheduler::unlock(); // Clear the timeout. It is irrelevant whether the alarm has // actually gone off or not. self->clear_timer(); CYG_INSTRUMENT_CNTSEM( WOKE, this, count ); switch( self->get_wake_reason() ) { case Cyg_Thread::TIMEOUT: result = false; CYG_INSTRUMENT_CNTSEM( TIMEOUT, this, count); break; case Cyg_Thread::DESTRUCT: case Cyg_Thread::BREAK: result = false; break; case Cyg_Thread::EXIT: self->exit(); break; default: break; } } CYG_REPORT_RETVAL( result ); return result; } #endif // CYGFUN_KERNEL_THREADS_TIMER // ------------------------------------------------------------------------- // Try to decrement, but fail if not possible cyg_bool Cyg_Counting_Semaphore2::trywait() { CYG_REPORT_FUNCTION(); cyg_bool result = true; // Prevent preemption Cyg_Scheduler::lock(); if( 0 < count ) count--; else result = false; CYG_INSTRUMENT_CNTSEM( TRY, this, result ); // Unlock the scheduler and maybe switch threads Cyg_Scheduler::unlock(); CYG_REPORT_RETVAL( result ); return result; } // ------------------------------------------------------------------------- // Increment count void Cyg_Counting_Semaphore2::post() { CYG_REPORT_FUNCTION(); // Prevent preemption Cyg_Scheduler::lock(); CYG_INSTRUMENT_CNTSEM( POST, this, 0 ); if( queue.empty() ) { count++; } else { // The queue is non-empty, so grab the next // thread from it and wake it up. The waiter // won't decrement the count when he is awakened, // for we never incremented it in the first place Cyg_Thread *thread = queue.dequeue(); thread->set_wake_reason( Cyg_Thread::DONE ); thread->wake(); CYG_INSTRUMENT_CNTSEM( WAKE, this, thread ); } // Unlock the scheduler and maybe switch threads Cyg_Scheduler::unlock(); CYG_REPORT_RETURN(); } // ------------------------------------------------------------------------- // Get current count value cyg_count32 Cyg_Counting_Semaphore2::peek() const { // This is a single read of the value of count. // This is already atomic, hence there is no need // to lock the scheduler. return count; } // ------------------------------------------------------------------------- // EOF sync/cnt_sem2.cxx
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