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//========================================================================== // // sync/bin_sem.cxx // // Binary 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_Binary_Semaphore implementation // Description: This file contains the implementations of the binary 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/sema.hxx> // our header #include <cyg/kernel/sched.inl> // scheduler inlines // ------------------------------------------------------------------------- Cyg_Binary_Semaphore::Cyg_Binary_Semaphore ( cyg_bool init_state ) { state = init_state; } // ------------------------------------------------------------------------- Cyg_Binary_Semaphore::~Cyg_Binary_Semaphore ( ) { CYG_ASSERT( queue.empty(), "Destroying semaphore with waiting threads"); } // ------------------------------------------------------------------------- cyg_bool Cyg_Binary_Semaphore::wait() { cyg_bool result = true; Cyg_Thread *self = Cyg_Thread::self(); // Prevent preemption Cyg_Scheduler::lock(); CYG_INSTRUMENT_BINSEM( CLAIM, this, state ); while( !state && result ) { self->set_sleep_reason( Cyg_Thread::WAIT ); self->sleep(); queue.enqueue( self ); CYG_INSTRUMENT_BINSEM( WAIT, this, 0 ); // Allow other threads to run Cyg_Scheduler::reschedule(); CYG_INSTRUMENT_BINSEM( WOKE, this, state ); 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; } } if( result ) state = false; // Unlock the scheduler and maybe switch threads Cyg_Scheduler::unlock(); return result; } // ------------------------------------------------------------------------- // Wait until the state can be set false or timeout #ifdef CYGFUN_KERNEL_THREADS_TIMER cyg_bool Cyg_Binary_Semaphore::wait( cyg_tick_count timeout ) { cyg_bool result = true; Cyg_Thread *self = Cyg_Thread::self(); // Prevent preemption Cyg_Scheduler::lock(); CYG_INSTRUMENT_BINSEM( CLAIM, this, state ); // Set the timer _once_ outside the loop. self->set_timer( timeout, Cyg_Thread::TIMEOUT ); // If the timeout is in the past, the wake reason will have been // set to something other than NONE already. If the semaphore is // not available, set the result false to force an immediate // return. If it is available, then go ahead and claim it. if( self->get_wake_reason() != Cyg_Thread::NONE && !state ) result = false; while ( !state && result ) { // must reset the sleep reason every time self->set_sleep_reason( Cyg_Thread::TIMEOUT ); self->sleep(); queue.enqueue( self ); CYG_INSTRUMENT_BINSEM( WAIT, this, 0 ); // Allow other threads to run Cyg_Scheduler::reschedule(); CYG_INSTRUMENT_BINSEM( WOKE, this, state ); switch( self->get_wake_reason() ) { case Cyg_Thread::TIMEOUT: result = false; CYG_INSTRUMENT_BINSEM( TIMEOUT, this, state); break; case Cyg_Thread::DESTRUCT: case Cyg_Thread::BREAK: result = false; break; case Cyg_Thread::EXIT: self->exit(); break; default: break; } } // Clear the timeout. It is irrelevant whether the alarm has // actually gone off or not. self->clear_timer(); if( result ) state = false; // Unlock the scheduler and maybe switch threads Cyg_Scheduler::unlock(); return result; } #endif // CYGFUN_KERNEL_THREADS_TIMER // ------------------------------------------------------------------------- cyg_bool Cyg_Binary_Semaphore::trywait() { cyg_bool result = true; // Prevent preemption Cyg_Scheduler::lock(); if( state ) state = false; else result = false; CYG_INSTRUMENT_BINSEM( TRY, this, result ); // Unlock the scheduler and maybe switch threads Cyg_Scheduler::unlock(); return result; } // ------------------------------------------------------------------------- void Cyg_Binary_Semaphore::post() { // Prevent preemption Cyg_Scheduler::lock(); CYG_INSTRUMENT_BINSEM( POST, this, 0 ); state = true; if( !queue.empty() ) { // The queue is non-empty, so grab the next // thread from it and wake it up. The waiter // will clear the flag. Cyg_Thread *thread = queue.dequeue(); thread->set_wake_reason( Cyg_Thread::DONE ); thread->wake(); CYG_INSTRUMENT_BINSEM( WAKE, this, thread ); } // Unlock the scheduler and maybe switch threads Cyg_Scheduler::unlock(); } // ------------------------------------------------------------------------- cyg_bool Cyg_Binary_Semaphore::posted() { // This is a single read of the value of state. // This is already atomic, hence there is no need // to lock the scheduler. return state; } // ------------------------------------------------------------------------- // EOF sync/bin_sem.cxx