source: src/libcfa/concurrency/monitor.c @ 95448f1e

//                              -*- Mode: CFA -*-
//
// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// monitor_desc.c --
//
// Author           : Thierry Delisle
// Created On       : Thd Feb 23 12:27:26 2017
// Last Modified By : Thierry Delisle
// Last Modified On : --
// Update Count     : 0
//

#include "monitor"

#include "kernel_private.h"

extern "C" {
        void __enter_monitor_desc(monitor_desc * this) {
                lock( &this->lock );
                thread_desc * thrd = this_thread();

                if( !this->owner ) {
                        //No one has the monitor, just take it
                        this->owner = thrd;
                        this->recursion = 1;
                }
                else if( this->owner == thrd) {
                        //We already have the monitor, just not how many times we took it
                        assert( this->recursion > 0 );
                        this->recursion += 1;
                }
                else {
                        //Some one else has the monitor, wait in line for it
                        append( &this->entry_queue, thrd );
                        ScheduleInternal( &this->lock );

                        //ScheduleInternal will unlock spinlock, no need to unlock ourselves
                        return; 
                }

                unlock( &this->lock );
        }

        void __leave_monitor_desc(monitor_desc * this) {
                lock( &this->lock );

                thread_desc * thrd = this_thread();
                assert( thrd == this->owner );

                //Leaving a recursion level, decrement the counter
                this->recursion -= 1;

                //If we left the last level of recursion it means we are changing who owns the monitor
                thread_desc * new_owner = 0;
                if( this->recursion == 0) {
                        //Get the next thread in the list
                        new_owner = this->owner = pop_head( &this->entry_queue );

                        //We are passing the monitor to someone else, which means recursion level is not 0
                        this->recursion = new_owner ? 1 : 0;
                }       

                unlock( &this->lock );

                //If we have a new owner, we need to wake-up the thread
                if( new_owner ) {
                        ScheduleThread( new_owner );
                }
        }
}

void enter(monitor_desc ** monitors, int count) {
        for(int i = 0; i < count; i++) {
                __enter_monitor_desc( monitors[i] );
        }
}

void leave(monitor_desc ** monitors, int count) {
        for(int i = count - 1; i >= 0; i--) {
                __leave_monitor_desc( monitors[i] );
        }
}