source: libcfa/src/concurrency/monitor.cfa @ e25ef8c

//
// 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.cfa --
//
// Author           : Thierry Delisle
// Created On       : Thd Feb 23 12:27:26 2017
// Last Modified By : Peter A. Buhr
// Last Modified On : Wed Nov 27 12:13:14 2024
// Update Count     : 72
//

#define __cforall_thread__

#include "monitor.hfa"

#include <stdlib.hfa>
#include <inttypes.h>

#include "kernel/private.hfa"

#include "bits/algorithm.hfa"

//-----------------------------------------------------------------------------
// Forward declarations
static inline void __set_owner( monitor$ * this, thread$ * owner );
static inline void __set_owner( monitor$ * storage [], __lock_size_t count, thread$ * owner );
static inline void set_mask( monitor$ * storage [], __lock_size_t count, const __waitfor_mask_t & mask );
static inline void reset_mask( monitor$ * this );

static inline thread$ * next_thread( monitor$ * this );
static inline bool is_accepted( monitor$ * this, const __monitor_group_t & monitors );

static inline void lock_all( __spinlock_t * locks [], __lock_size_t count );
static inline void lock_all( monitor$ * source [], __spinlock_t * /*out*/ locks [], __lock_size_t count );
static inline void unlock_all( __spinlock_t * locks [], __lock_size_t count );
static inline void unlock_all( monitor$ * locks [], __lock_size_t count );

static inline void save( monitor$ * ctx [], __lock_size_t count, __spinlock_t * locks [], unsigned int /*out*/ recursions [], __waitfor_mask_t /*out*/ masks [] );
static inline void restore( monitor$ * ctx [], __lock_size_t count, __spinlock_t * locks [], unsigned int /*in */ recursions [], __waitfor_mask_t /*in */ masks [] );

static inline void ?{}(__condition_node_t & this, thread$ * waiting_thread, __lock_size_t count, uintptr_t user_info );
static inline void ?{}(__condition_criterion_t & this );
static inline void ?{}(__condition_criterion_t & this, monitor$ * target, __condition_node_t * owner );

static inline void init( __lock_size_t count, monitor$ * monitors [], __condition_node_t & waiter, __condition_criterion_t criteria [] );
static inline void init_push( __lock_size_t count, monitor$ * monitors [], __condition_node_t & waiter, __condition_criterion_t criteria [] );

static inline thread$ * check_condition ( __condition_criterion_t * );
static inline void brand_condition( condition & );
static inline [thread$ *, int] search_entry_queue( const __waitfor_mask_t &, monitor$ * monitors [], __lock_size_t count );

forall(T & | sized( T ))
static inline __lock_size_t insert_unique( T * array [], __lock_size_t & size, T * val );
static inline __lock_size_t count_max( const __waitfor_mask_t & mask );
static inline __lock_size_t aggregate( monitor$ * storage [], const __waitfor_mask_t & mask );

//-----------------------------------------------------------------------------
// Useful defines
#define wait_ctx( thrd, user_info )                                                     /* Create the necessary information to use the signaller stack */ \
        __condition_node_t waiter = { thrd, count, user_info }; /* Create the node specific to this wait operation */ \
        __condition_criterion_t criteria[count];                                /* Create the creteria this wait operation needs to wake up */ \
        init( count, monitors, waiter, criteria );                              /* Link everything together */

#define wait_ctx_primed( thrd, user_info )                                      /* Create the necessary information to use the signaller stack */ \
        __condition_node_t waiter = { thrd, count, user_info }; /* Create the node specific to this wait operation */ \
        __condition_criterion_t criteria[count];                                /* Create the creteria this wait operation needs to wake up */ \
        init_push( count, monitors, waiter, criteria );                 /* Link everything together and push it to the AS-Stack */

#define monitor_ctx( mons, cnt )                                                        /* Define that create the necessary struct for internal/external scheduling operations */ \
        monitor$ ** monitors = mons;                                                    /* Save the targeted monitors */ \
        __lock_size_t count = cnt;                                                              /* Save the count to a local variable */ \
        unsigned int recursions[count];                                                 /* Save the current recursion levels to restore them later */ \
        __waitfor_mask_t masks[count];                                                  /* Save the current waitfor masks to restore them later */ \
        __spinlock_t * locks[count];                                                    /* We need to pass-in an array of locks to BlockInternal */

#define monitor_save    save   ( monitors, count, locks, recursions, masks )
#define monitor_restore restore( monitors, count, locks, recursions, masks )


//-----------------------------------------------------------------------------
// Enter/Leave routines
// Enter single monitor
static void __enter( monitor$ * this, const __monitor_group_t & group ) {
        thread$ * thrd = active_thread();

        // Lock the monitor spinlock
        lock( this->lock __cfaabi_dbg_ctx2 );

        __cfaabi_dbg_print_safe( "Kernel : %10p Entering mon %p (%p)\n", thrd, this, this->owner);

        if ( unlikely(0 != (0x1 & (uintptr_t)this->owner)) ) {
                abort( "Attempt by thread \"%.256s\" (%p) to access joined monitor %p.", thrd->self_cor.name, thrd, this );
        } else if ( !this->owner ) {
                // No one has the monitor, just take it
                __set_owner( this, thrd );

                __cfaabi_dbg_print_safe( "Kernel :  mon is free \n" );
        } else if ( this->owner == thrd) {
                // We already have the monitor, just note how many times we took it
                this->recursion += 1;

                __cfaabi_dbg_print_safe( "Kernel :  mon already owned \n" );
        } else if ( is_accepted( this, group) ) {
                // Some one was waiting for us, enter
                __set_owner( this, thrd );

                // Reset mask
                reset_mask( this );

                __cfaabi_dbg_print_safe( "Kernel :  mon accepts \n" );
        } else {
                __cfaabi_dbg_print_safe( "Kernel :  blocking \n" );

                // Some one else has the monitor, wait in line for it
                /* paranoid */ verify( thrd->user_link.next == 0p );
                append( this->entry_queue, thrd );
                /* paranoid */ verify( thrd->user_link.next == 1p );

                unlock( this->lock );
                park();

                __cfaabi_dbg_print_safe( "Kernel : %10p Entered  mon %p\n", thrd, this);

                /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
                return;
        }

        __cfaabi_dbg_print_safe( "Kernel : %10p Entered  mon %p\n", thrd, this);

        /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
        /* paranoid */ verify( this->lock.lock );

        // Release the lock and leave
        unlock( this->lock );
        return;
}

static void __dtor_enter( monitor$ * this, fptr_t func, bool join ) {
        thread$ * thrd = active_thread();
        #if defined( __CFA_WITH_VERIFY__ )
                bool is_thrd = this == &thrd->self_mon;
        #endif

        // Lock the monitor spinlock
        lock( this->lock __cfaabi_dbg_ctx2 );

        __cfaabi_dbg_print_safe( "Kernel : %10p Entering dtor for mon %p (%p)\n", thrd, this, this->owner);


        if ( !this->owner ) {
                __cfaabi_dbg_print_safe( "Kernel : Destroying free mon %p\n", this);

                // No one has the monitor, just take it
                __set_owner( this, thrd );

                /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
                /* paranoid */ verify( !is_thrd || thrd->state == Halted || thrd->state == Cancelled );

                unlock( this->lock );
                return;
        } else if ( this->owner == thrd && !join) {
                // We already have the monitor... but where about to destroy it so the nesting will fail
                // Abort!
                abort( "Attempt to destroy monitor %p by thread \"%.256s\" (%p) in nested mutex.", this, thrd->self_cor.name, thrd );
        }
        // SKULLDUGGERY: join will act as a dtor so it would normally trigger to above check
        // because join will not release the monitor after it executed.
        // to avoid that it sets the owner to the special value thrd | 1p before exiting
        else if ( this->owner == (thread$*)(1 | (uintptr_t)thrd) ) {
                // restore the owner and just return
                __cfaabi_dbg_print_safe( "Kernel : Destroying free mon %p\n", this);

                // No one has the monitor, just take it
                __set_owner( this, thrd );

                /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
                /* paranoid */ verify( !is_thrd || thrd->state == Halted || thrd->state == Cancelled );

                unlock( this->lock );
                return;
        }

        // The monitor is busy, if this is a thread and the thread owns itself, it better be active
        /* paranoid */ verify( !is_thrd || this->owner != thrd || (thrd->state != Halted && thrd->state != Cancelled) );

        __lock_size_t count = 1;
        monitor$ ** monitors = &this;
        __monitor_group_t group = { &this, 1, func };
        if ( is_accepted( this, group) ) {
                __cfaabi_dbg_print_safe( "Kernel :  mon accepts dtor, block and signal it \n" );

                // Wake the thread that is waiting for this
                __condition_criterion_t * urgent = pop( this->signal_stack );
                /* paranoid */ verify( urgent );

                // Reset mask
                reset_mask( this );

                // Create the node specific to this wait operation
                wait_ctx_primed( thrd, 0 )

                // Some one else has the monitor, wait for him to finish and then run
                unlock( this->lock );

                // Release the next thread
                /* paranoid */ verifyf( urgent->owner->waiting_thread == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
                unpark( urgent->owner->waiting_thread );

                // Park current thread waiting
                park();

                // Some one was waiting for us, enter
                /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );

                __cfaabi_dbg_print_safe( "Kernel : Destroying %p\n", this);
                return;
        } else {
                __cfaabi_dbg_print_safe( "Kernel :  blocking \n" );

                wait_ctx( thrd, 0 )
                this->dtor_node = &waiter;

                // Some one else has the monitor, wait in line for it
                /* paranoid */ verify( thrd->user_link.next == 0p );
                append( this->entry_queue, thrd );
                /* paranoid */ verify( thrd->user_link.next == 1p );
                unlock( this->lock );

                // Park current thread waiting
                park();

                /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
                return;
        }
}

// Leave single monitor
static void __leave( monitor$ * this ) {
        // Lock the monitor spinlock
        lock( this->lock __cfaabi_dbg_ctx2 );

        __cfaabi_dbg_print_safe( "Kernel : %10p Leaving mon %p (%p)\n", active_thread(), this, this->owner);

        /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );

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

        // If we haven't left the last level of recursion
        // it means we don't need to do anything
        if ( this->recursion != 0) {
                __cfaabi_dbg_print_safe( "Kernel :  recursion still %d\n", this->recursion);
                unlock( this->lock );
                return;
        }

        // Get the next thread, will be null on low contention monitor
        thread$ * new_owner = next_thread( this );

        // Check the new owner is consistent with who we wake-up
        // new_owner might be null even if someone owns the monitor when the owner is still waiting for another monitor
        /* paranoid */ verifyf( !new_owner || new_owner == this->owner, "Expected owner to be %p, got %p (m: %p)", new_owner, this->owner, this );

        // We can now let other threads in safely
        unlock( this->lock );

        //We need to wake-up the thread
        /* paranoid */ verifyf( !new_owner || new_owner == this->owner, "Expected owner to be %p, got %p (m: %p)", new_owner, this->owner, this );
        unpark( new_owner );
}

// Leave single monitor for the last time
static void __dtor_leave( monitor$ * this, bool join ) {
        __cfaabi_dbg_debug_do(
                if ( active_thread() != this->owner ) {
                        abort( "Destroyed monitor %p has inconsistent owner, expected %p got %p.\n", this, active_thread(), this->owner);
                }
                if ( this->recursion != 1  && !join ) {
                        abort( "Destroyed monitor %p has %d outstanding nested calls.\n", this, this->recursion - 1);
                }
        )

        this->owner = (thread$*)(1 | (uintptr_t)this->owner);
}

void __thread_finish( thread$ * thrd ) {
        monitor$ * this = &thrd->self_mon;

        // Lock the monitor now
        /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd->canary );
        /* paranoid */ verify( this->lock.lock );
        /* paranoid */ verify( thrd->context.SP );
        /* paranoid */ verifyf( ((uintptr_t)thrd->context.SP) > ((uintptr_t)__get_stack(thrd->curr_cor)->limit), "ERROR : thread$ %p has been corrupted.\n StackPointer too large.\n", thrd );
        /* paranoid */ verifyf( ((uintptr_t)thrd->context.SP) < ((uintptr_t)__get_stack(thrd->curr_cor)->base ), "ERROR : thread$ %p has been corrupted.\n StackPointer too small.\n", thrd );
        /* paranoid */ verify( ! __preemption_enabled() );

        /* paranoid */ verifyf( thrd == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", thrd, this->owner, this->recursion, this );
        /* paranoid */ verify( thrd->state == Halting );
        /* paranoid */ verify( this->recursion == 1 );

        // Leaving a recursion level, decrement the counter
        this->recursion -= 1;
        this->owner = 0p;

        // Fetch the next thread, can be null
        thread$ * new_owner = next_thread( this );

        // Mark the state as fully halted
        thrd->state = Halted;

        // Release the monitor lock
        unlock( this->lock );

        // Unpark the next owner if needed
        /* paranoid */ verifyf( !new_owner || new_owner == this->owner, "Expected owner to be %p, got %p (m: %p)", new_owner, this->owner, this );
        /* paranoid */ verify( ! __preemption_enabled() );
        /* paranoid */ verify( thrd->state == Halted );
        unpark( new_owner );
}

// Enter multiple monitor
// relies on the monitor array being sorted
static inline void enter( __monitor_group_t monitors ) {
        for ( i; monitors.size ) {
                __enter( monitors[i], monitors );
        }
}

// Leave multiple monitor
// relies on the monitor array being sorted
static inline void leave(monitor$ * monitors [], __lock_size_t count) {
        for ( i; -~= count - 1 ) {
                __leave( monitors[i] );
        }
}

// Ctor for monitor guard
// Sorts monitors before entering
void ?{}( monitor_guard_t & this, monitor$ * m [], __lock_size_t count, fptr_t func ) libcfa_public {
        thread$ * thrd = active_thread();

        // Store current array
        this.m = m;
        this.count = count;

        // Sort monitors based on address
        __libcfa_small_sort(this.m, count);

        // Save previous thread context
        this.prev = thrd->monitors;

        // Update thread context (needed for conditions)
        (thrd->monitors){m, count, func};

        // __cfaabi_dbg_print_safe( "MGUARD : enter %d\n", count);

        // Enter the monitors in order
        __monitor_group_t group = {this.m, this.count, func};
        enter( group );

        // __cfaabi_dbg_print_safe( "MGUARD : entered\n" );
}

void ?{}( monitor_guard_t & this, monitor$ * m [], __lock_size_t count ) libcfa_public {
        this{ m, count, 0p };
}


// Dtor for monitor guard
void ^?{}( monitor_guard_t & this ) libcfa_public {
        // __cfaabi_dbg_print_safe( "MGUARD : leaving %d\n", this.count);

        // Leave the monitors in order
        leave( this.m, this.count );

        // __cfaabi_dbg_print_safe( "MGUARD : left\n" );

        // Restore thread context
        active_thread()->monitors = this.prev;
}

// Ctor for monitor guard
// Sorts monitors before entering
void ?{}( monitor_dtor_guard_t & this, monitor$ * m [], fptr_t func, bool join ) libcfa_public {
        // optimization
        thread$ * thrd = active_thread();

        // Store current array
        this.m = *m;

        // Save previous thread context
        this.prev = thrd->monitors;

        // Save whether we are in a join or not
        this.join = join;

        // Update thread context (needed for conditions)
        (thrd->monitors){m, 1, func};

        __dtor_enter( this.m, func, join );
}

// Dtor for monitor guard
void ^?{}( monitor_dtor_guard_t & this ) libcfa_public {
        // Leave the monitors in order
        __dtor_leave( this.m, this.join );

        // Restore thread context
        active_thread()->monitors = this.prev;
}

//-----------------------------------------------------------------------------
// Internal scheduling types
static void ?{}(__condition_node_t & this, thread$ * waiting_thread, __lock_size_t count, uintptr_t user_info ) {
        this.waiting_thread = waiting_thread;
        this.count = count;
        this.next = 0p;
        this.user_info = user_info;
}

static void ?{}(__condition_criterion_t & this ) with( this ) {
        ready  = false;
        target = 0p;
        owner  = 0p;
        next   = 0p;
}

static void ?{}(__condition_criterion_t & this, monitor$ * target, __condition_node_t & owner ) {
        this.ready  = false;
        this.target = target;
        this.owner  = &owner;
        this.next   = 0p;
}

//-----------------------------------------------------------------------------
// Internal scheduling
void wait( condition & this, uintptr_t user_info = 0 ) libcfa_public {
        brand_condition( this );

        // Check that everything is as expected
        assertf( this.monitors != 0p, "Waiting with no monitors (%p)", this.monitors );
        verifyf( this.monitor_count != 0, "Waiting with 0 monitors (%"PRIiFAST16")", this.monitor_count );
        verifyf( this.monitor_count < 32u, "Excessive monitor count (%"PRIiFAST16")", this.monitor_count );

        // Create storage for monitor context
        monitor_ctx( this.monitors, this.monitor_count );       // creates monitors, count, recursions, masks, locks

        // Create the node specific to this wait operation
        wait_ctx( active_thread(), user_info );

        // Append the current wait operation to the ones already queued on the condition
        // We don't need locks for that since conditions must always be waited on inside monitor mutual exclusion
        /* paranoid */ verify( waiter.next == 0p );
        append( this.blocked, &waiter );
        /* paranoid */ verify( waiter.next == 1p );

        // Lock all monitors (aggregates the locks as well)
        lock_all( monitors, locks, count );

        // Find the next thread(s) to run
        __lock_size_t thread_count = 0;
        thread$ * threads[ count ];
        __builtin_memset( threads, 0, sizeof( threads ) );

        // Save monitor states
        monitor_save;

        // Remove any duplicate threads
        for ( i; count ) {
                thread$ * new_owner = next_thread( monitors[i] );
                insert_unique( threads, thread_count, new_owner );
        }

        // Unlock the locks, we don't need them anymore
        for ( i; count ) {
                unlock( *locks[i] );
        }

        // Wake the threads
        for ( i; thread_count ) {
                unpark( threads[i] );
        }

        // Everything is ready to go to sleep
        park();

        // We are back, restore the owners and recursions
        monitor_restore;
}

bool signal( condition & this ) libcfa_public {
        if ( is_empty( this ) ) { return false; }

        //Check that everything is as expected
        verify( this.monitors );
        verify( this.monitor_count != 0 );

        //Some more checking in debug
        __cfaabi_dbg_debug_do(
                thread$ * this_thrd = active_thread();
                if ( this.monitor_count != this_thrd->monitors.size ) {
                        abort( "Signal on condition %p made with different number of monitor(s), expected %zi got %zi", &this, this.monitor_count, this_thrd->monitors.size );
                }

                for ( i; this.monitor_count ) {
                        if ( this.monitors[i] != this_thrd->monitors[i] ) {
                                abort( "Signal on condition %p made with different monitor, expected %p got %p", &this, this.monitors[i], this_thrd->monitors[i] );
                        }
                }
        );

        __lock_size_t count = this.monitor_count;

        // Lock all monitors
        lock_all( this.monitors, 0p, count );

        //Pop the head of the waiting queue
        __condition_node_t * node = pop_head( this.blocked );

        //Add the thread to the proper AS stack
        for ( i; count ) {
                __condition_criterion_t * crit = &node->criteria[i];
                assert( !crit->ready );
                push( crit->target->signal_stack, crit );
        }

        //Release
        unlock_all( this.monitors, count );

        return true;
}

bool signal_block( condition & this ) libcfa_public {
        if ( !this.blocked.head ) { return false; }

        //Check that everything is as expected
        verifyf( this.monitors != 0p, "Waiting with no monitors (%p)", this.monitors );
        verifyf( this.monitor_count != 0, "Waiting with 0 monitors (%"PRIiFAST16")", this.monitor_count );

        // Create storage for monitor context
        monitor_ctx( this.monitors, this.monitor_count );       // creates monitors, count, recursions, masks, locks

        // Lock all monitors (aggregates the locks them as well)
        lock_all( monitors, locks, count );

        // Create the node specific to this wait operation
        wait_ctx_primed( active_thread(), 0 )

        //save contexts
        monitor_save;

        //Find the thread to run
        thread$ * signallee = pop_head( this.blocked )->waiting_thread;
        __set_owner( monitors, count, signallee );

        __cfaabi_dbg_print_buffer_decl( "Kernel : signal_block condition %p (s: %p)\n", &this, signallee );

        // unlock all the monitors
        unlock_all( locks, count );

        // unpark the thread we signalled
        unpark( signallee );

        //Everything is ready to go to sleep
        park();

        // WE WOKE UP

        __cfaabi_dbg_print_buffer_local( "Kernel :   signal_block returned\n" );

        //We are back, restore the masks and recursions
        monitor_restore;

        return true;
}

// Access the user_info of the thread waiting at the front of the queue
uintptr_t front( condition & this ) libcfa_public {
        verifyf( !is_empty(this),
                "Attempt to access user data on an empty condition.\n"
                "Possible cause is not checking if the condition is empty before reading stored data."
        );
        return ((typeof(this.blocked.head))this.blocked.head)->user_info;
}

//-----------------------------------------------------------------------------
// External scheduling
// cases to handle :
//      - target already there :
//              block and wake
//      - dtor already there
//              put thread on signaller stack
//      - non-blocking
//              return else
//      - timeout
//              return timeout
//      - block
//              setup mask
//              block
void __waitfor_internal( const __waitfor_mask_t & mask, int duration ) libcfa_public {
        // This statment doesn't have a contiguous list of monitors...
        // Create one!
        __lock_size_t max = count_max( mask );
        monitor$ * mon_storage[max];
        __builtin_memset( mon_storage, 0, sizeof( mon_storage ) );
        __lock_size_t actual_count = aggregate( mon_storage, mask );

        __cfaabi_dbg_print_buffer_decl( "Kernel : waitfor %"PRIdFAST16" (s: %"PRIdFAST16", m: %"PRIdFAST16")\n", actual_count, mask.size, (__lock_size_t)max);

        if (actual_count == 0) return;

        __cfaabi_dbg_print_buffer_local( "Kernel : waitfor internal proceeding\n" );

        // Create storage for monitor context
        monitor_ctx( mon_storage, actual_count );                       // creates monitors, count, recursions, masks, locks

        // Lock all monitors (aggregates the locks as well)
        lock_all( monitors, locks, count );

        {
                // Check if the entry queue
                thread$ * next; int index;
                [next, index] = search_entry_queue( mask, monitors, count );

                if ( next ) {
                        *mask.accepted = index;
                        __acceptable_t& accepted = mask[index];
                        if ( accepted.is_dtor ) {
                                __cfaabi_dbg_print_buffer_local( "Kernel : dtor already there\n" );
                                verifyf( accepted.size == 1,  "ERROR: Accepted dtor has more than 1 mutex parameter." );

                                monitor$ * mon2dtor = accepted[0];
                                verifyf( mon2dtor->dtor_node, "ERROR: Accepted monitor has no dtor_node." );

                                __condition_criterion_t * dtor_crit = mon2dtor->dtor_node->criteria;
                                push( mon2dtor->signal_stack, dtor_crit );

                                unlock_all( locks, count );
                        }
                        else {
                                __cfaabi_dbg_print_buffer_local( "Kernel : thread present, baton-passing\n" );

                                // Create the node specific to this wait operation
                                wait_ctx_primed( active_thread(), 0 );

                                // Save monitor states
                                monitor_save;

                                __cfaabi_dbg_print_buffer_local( "Kernel :  baton of %"PRIdFAST16" monitors : ", count );
                                #ifdef __CFA_DEBUG_PRINT__
                                        for ( i; count ) {
                                                __cfaabi_dbg_print_buffer_local( "%p %p ", monitors[i], monitors[i]->signal_stack.top );
                                        }
                                #endif
                                __cfaabi_dbg_print_buffer_local( "\n" );

                                // Set the owners to be the next thread
                                __set_owner( monitors, count, next );

                                // unlock all the monitors
                                unlock_all( locks, count );

                                // unpark the thread we signalled
                                unpark( next );

                                //Everything is ready to go to sleep
                                park();

                                // We are back, restore the owners and recursions
                                monitor_restore;

                                __cfaabi_dbg_print_buffer_local( "Kernel : thread present, returned\n" );
                        }

                        __cfaabi_dbg_print_buffer_local( "Kernel : accepted %d\n", *mask.accepted);
                        return;
                }
        }


        if ( duration == 0 ) {
                __cfaabi_dbg_print_buffer_local( "Kernel : non-blocking, exiting\n" );

                unlock_all( locks, count );

                __cfaabi_dbg_print_buffer_local( "Kernel : accepted %d\n", *mask.accepted);
                return;
        }


        verifyf( duration < 0, "Timeout on waitfor statments not supported yet." );

        __cfaabi_dbg_print_buffer_local( "Kernel : blocking waitfor\n" );

        // Create the node specific to this wait operation
        wait_ctx_primed( active_thread(), 0 );

        monitor_save;
        set_mask( monitors, count, mask );

        for ( i; count ) {
                verify( monitors[i]->owner == active_thread() );
        }

        // unlock all the monitors
        unlock_all( locks, count );

        //Everything is ready to go to sleep
        park();


        // WE WOKE UP


        //We are back, restore the masks and recursions
        monitor_restore;

        __cfaabi_dbg_print_buffer_local( "Kernel : exiting\n" );

        __cfaabi_dbg_print_buffer_local( "Kernel : accepted %d\n", *mask.accepted);
}

//-----------------------------------------------------------------------------
// Utilities

static inline void __set_owner( monitor$ * this, thread$ * owner ) {
        /* paranoid */ verify( this->lock.lock );

        //Pass the monitor appropriately
        this->owner = owner;

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

static inline void __set_owner( monitor$ * monitors [], __lock_size_t count, thread$ * owner ) {
        /* paranoid */ verify ( monitors[0]->lock.lock );
        /* paranoid */ verifyf( monitors[0]->owner == active_thread(), "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), monitors[0]->owner, monitors[0]->recursion, monitors[0] );
        monitors[0]->owner        = owner;
        monitors[0]->recursion    = 1;
        for ( i; 1~count ) {
                /* paranoid */ verify ( monitors[i]->lock.lock );
                /* paranoid */ verifyf( monitors[i]->owner == active_thread(), "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), monitors[i]->owner, monitors[i]->recursion, monitors[i] );
                monitors[i]->owner        = owner;
                monitors[i]->recursion    = 0;
        }
}

static inline void set_mask( monitor$ * storage [], __lock_size_t count, const __waitfor_mask_t & mask ) {
        for ( i; count) {
                storage[i]->mask = mask;
        }
}

static inline void reset_mask( monitor$ * this ) {
        this->mask.accepted = 0p;
        this->mask.data = 0p;
        this->mask.size = 0;
}

static inline thread$ * next_thread( monitor$ * this ) {
        //Check the signaller stack
        __cfaabi_dbg_print_safe( "Kernel :  mon %p AS-stack top %p\n", this, this->signal_stack.top);
        __condition_criterion_t * urgent = pop( this->signal_stack );
        if ( urgent ) {
                //The signaller stack is not empty,
                //regardless of if we are ready to baton pass,
                //we need to set the monitor as in use
                /* paranoid */ verifyf( !this->owner || active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
                __set_owner( this,  urgent->owner->waiting_thread );

                return check_condition( urgent );
        }

        // No signaller thread
        // Get the next thread in the entry_queue
        thread$ * new_owner = pop_head( this->entry_queue );
        /* paranoid */ verifyf( !this->owner || active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
        /* paranoid */ verify( !new_owner || new_owner->user_link.next == 0p );
        __set_owner( this, new_owner );

        return new_owner;
}

static inline bool is_accepted( monitor$ * this, const __monitor_group_t & group ) {
        __acceptable_t * it = this->mask.data; // Optim
        __lock_size_t count = this->mask.size;

        // Check if there are any acceptable functions
        if ( !it ) return false;

        // If this isn't the first monitor to test this, there is no reason to repeat the test.
        if ( this != group[0] ) return group[0]->mask.accepted >= 0;

        // For all acceptable functions check if this is the current function.
        for ( __lock_size_t i = 0; i < count; i++, it++ ) {
                if ( *it == group ) {
                        *this->mask.accepted = i;
                        return true;
                }
        }

        // No function matched
        return false;
}

static inline void init( __lock_size_t count, monitor$ * monitors [], __condition_node_t & waiter, __condition_criterion_t criteria [] ) {
        for ( i; count ) {
                (criteria[i]){ monitors[i], waiter };
        }

        waiter.criteria = criteria;
}

static inline void init_push( __lock_size_t count, monitor$ * monitors [], __condition_node_t & waiter, __condition_criterion_t criteria [] ) {
        for ( i; count ) {
                (criteria[i]){ monitors[i], waiter };
                __cfaabi_dbg_print_safe( "Kernel :  target %p = %p\n", criteria[i].target, &criteria[i] );
                push( criteria[i].target->signal_stack, &criteria[i] );
        }

        waiter.criteria = criteria;
}

static inline void lock_all( __spinlock_t * locks [], __lock_size_t count ) {
        for ( i; count ) {
                lock( *locks[i] __cfaabi_dbg_ctx2 );
        }
}

static inline void lock_all( monitor$ * source [], __spinlock_t * /*out*/ locks [], __lock_size_t count ) {
        for ( i; count ) {
                __spinlock_t * l = &source[i]->lock;
                lock( *l __cfaabi_dbg_ctx2 );
                if (locks) locks[i] = l;
        }
}

static inline void unlock_all( __spinlock_t * locks [], __lock_size_t count ) {
        for ( i; count ) {
                unlock( *locks[i] );
        }
}

static inline void unlock_all( monitor$ * locks [], __lock_size_t count ) {
        for ( i; count ) {
                unlock( locks[i]->lock );
        }
}

static inline void save(
        monitor$ * ctx [],
        __lock_size_t count,
        __attribute((unused)) __spinlock_t * locks [],
        unsigned int /*out*/ recursions [],
        __waitfor_mask_t /*out*/ masks []
) {
        for ( i; count ) {
                recursions[i] = ctx[i]->recursion;
                masks[i] = ctx[i]->mask;
        }
}

static inline void restore(
        monitor$ * ctx [],
        __lock_size_t count,
        __spinlock_t * locks [],
        unsigned int /*out*/ recursions [],
        __waitfor_mask_t /*out*/ masks []
) {
        lock_all( locks, count );
        for ( i; count ) {
                ctx[i]->recursion = recursions[i];
                ctx[i]->mask = masks[i];
        }
        unlock_all( locks, count );
}

// Function has 2 different behavior
// 1 - Marks a monitors as being ready to run
// 2 - Checks if all the monitors are ready to run
//     if so return the thread to run
static inline thread$ * check_condition( __condition_criterion_t * target ) {
        __condition_node_t * node = target->owner;
        unsigned short count = node->count;
        __condition_criterion_t * criteria = node->criteria;

        bool ready2run = true;

        for ( i; count ) {
                // __cfaabi_dbg_print_safe( "Checking %p for %p\n", &criteria[i], target );
                if ( &criteria[i] == target ) {
                        criteria[i].ready = true;
                        // __cfaabi_dbg_print_safe( "True\n" );
                }

                ready2run = criteria[i].ready && ready2run;
        }

        __cfaabi_dbg_print_safe( "Kernel :  Runing %i (%p)\n", ready2run, ready2run ? (thread*)node->waiting_thread : (thread*)0p );
        return ready2run ? node->waiting_thread : 0p;
}

static inline void brand_condition( condition & this ) {
        thread$ * thrd = active_thread();
        if ( !this.monitors ) {
                // __cfaabi_dbg_print_safe( "Branding\n" );
                assertf( thrd->monitors.data != 0p, "No current monitor to brand condition %p", thrd->monitors.data );
                this.monitor_count = thrd->monitors.size;

                this.monitors = (monitor$ **)malloc( this.monitor_count * sizeof( *this.monitors ) );
                for ( i; this.monitor_count ) {
                        this.monitors[i] = thrd->monitors[i];
                }
        }
}

static inline [thread$ *, int] search_entry_queue( const __waitfor_mask_t & mask, monitor$ * monitors [], __lock_size_t count ) {
        __queue_t(thread$) & entry_queue = monitors[0]->entry_queue;

#if 0
        #if defined( __CFA_WITH_VERIFY__ )
                thread$ * last = 0p;
        #endif
        // For each thread in the entry-queue
        for ( thread$ ** thrd_it = &entry_queue.head; (*thrd_it) != 1p; thrd_it = &get_next(**thrd_it) ) {
                thread$ * curr = *thrd_it;

                /* paranoid */ verifyf( !last || last->user_link.next == curr, "search not making progress, from %p (%p) to %p",
                                                                last, last->user_link.next, curr );
                /* paranoid */ verifyf( curr != last, "search not making progress, from %p to %p", last, curr );

                // For each acceptable check if it matches
                int i = 0;
                __acceptable_t * end = end(mask);
                __acceptable_t * begin = begin(mask);
                for ( __acceptable_t * it = begin; it != end; it++, i++ ) {
                        // Check for match
                        if ( *it == curr->monitors ) {
                                // If match, return it after removeing it from the entry queue
                                return [remove( entry_queue, thrd_it ), i];
                        }
                }

                #if defined( __CFA_WITH_VERIFY__ )
                        last = curr;
                #endif
        }
#else
        // For each acceptable (respect lexical priority in waitfor statement)
        __acceptable_t * it = end(mask); it--;                          // end is passed the last node, so backup
        for ( int i = mask.size - 1; i >= 0; i -= 1, it-- ) {
                #if defined( __CFA_WITH_VERIFY__ )
                thread$ * last = 0p;
                #endif // __CFA_WITH_VERIFY__

                for ( thread$ ** thrd_it = &entry_queue.head; (*thrd_it) != 1p; thrd_it = &get_next(**thrd_it) ) {
                        thread$ * curr = *thrd_it;

                        /* paranoid */ verifyf( !last || last->user_link.next == curr, "search not making progress, from %p (%p) to %p",
                                                                        last, last->user_link.next, curr );
                        /* paranoid */ verifyf( curr != last, "search not making progress, from %p to %p", last, curr );

                        // For each thread in the entry-queue check for a match
                        if ( *it == curr->monitors ) {
                                // If match, return it after removing from the entry queue
                                return [remove( entry_queue, thrd_it ), i];
                        } // if

                        #if defined( __CFA_WITH_VERIFY__ )
                        last = curr;
                        #endif
                } // for
        } // for
#endif
        return [0, -1];
}

forall( T & | sized( T ) )
static inline __lock_size_t insert_unique( T * array [], __lock_size_t & size, T * val ) {
        if ( ! val ) return size;

        for ( __lock_size_t i; ~= size ) {
                if ( array[i] == val ) return size;
        }

        array[size] = val;
        return size += 1;
}

static inline __lock_size_t count_max( const __waitfor_mask_t & mask ) {
        __lock_size_t max = 0;
        for ( i; mask.size ) {
                __acceptable_t & accepted = mask[i];
                max += accepted.size;
        }
        return max;
}

static inline __lock_size_t aggregate( monitor$ * storage [], const __waitfor_mask_t & mask ) {
        __lock_size_t size = 0;
        for ( i; mask.size ) {
                __acceptable_t & accepted = mask[i];
                __libcfa_small_sort( accepted.data, accepted.size );
                for ( __lock_size_t j = 0; j < accepted.size; j++) {
                        insert_unique( storage, size, accepted[j] );
                }
        }
        // TODO insertion sort instead of this
        __libcfa_small_sort( storage, size );
        return size;
}

//-----------------------------------------------------------------------------
// Enter routine for mutex stmt
// Can't be accepted since a mutex stmt is effectively an anonymous routine
// Thus we do not need a monitor group
void lock( monitor$ * this ) libcfa_public {
        thread$ * thrd = active_thread();

        // Lock the monitor spinlock
        lock( this->lock __cfaabi_dbg_ctx2 );

        __cfaabi_dbg_print_safe( "Kernel : %10p Entering mon %p (%p)\n", thrd, this, this->owner);

        if ( unlikely(0 != (0x1 & (uintptr_t)this->owner)) ) {
                abort( "Attempt by thread \"%.256s\" (%p) to access joined monitor %p.", thrd->self_cor.name, thrd, this );
        } else if ( !this->owner ) {
                // No one has the monitor, just take it
                __set_owner( this, thrd );

                __cfaabi_dbg_print_safe( "Kernel :  mon is free \n" );
        } else if ( this->owner == thrd) {
                // We already have the monitor, just note how many times we took it
                this->recursion += 1;

                __cfaabi_dbg_print_safe( "Kernel :  mon already owned \n" );
        } else {
                __cfaabi_dbg_print_safe( "Kernel :  blocking \n" );

                // Some one else has the monitor, wait in line for it
                /* paranoid */ verify( thrd->user_link.next == 0p );
                append( this->entry_queue, thrd );
                /* paranoid */ verify( thrd->user_link.next == 1p );

                unlock( this->lock );
                park();

                __cfaabi_dbg_print_safe( "Kernel : %10p Entered  mon %p\n", thrd, this);

                /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
                return;
        }

        __cfaabi_dbg_print_safe( "Kernel : %10p Entered  mon %p\n", thrd, this);

        /* paranoid */ verifyf( active_thread() == this->owner, "Expected owner to be %p, got %p (r: %i, m: %p)", active_thread(), this->owner, this->recursion, this );
        /* paranoid */ verify( this->lock.lock );

        // Release the lock and leave
        unlock( this->lock );
        return;
}

// Leave routine for mutex stmt
// Is just a wrapper around __leave for the is_lock trait to see
void unlock( monitor$ * this ) libcfa_public { __leave( this ); }

// Local Variables: //
// mode: c //
// tab-width: 4 //
// End: //