source: src/libcfa/concurrency/monitor.c@ 6ac5223

//
// 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 : Peter A. Buhr
// Last Modified On : Mon Jul 31 14:59:05 2017
// Update Count     : 3
//

#include "monitor"

#include <stdlib>

#include "libhdr.h"
#include "kernel_private.h"

//-----------------------------------------------------------------------------
// Forward declarations
static inline void set_owner( monitor_desc * this, thread_desc * owner );
static inline thread_desc * next_thread( monitor_desc * this );
static inline int is_accepted( thread_desc * owner, monitor_desc * this, monitor_desc ** group, int group_cnt, void (*func)() );

static inline void lock_all( spinlock ** locks, unsigned short count );
static inline void lock_all( monitor_desc ** source, spinlock ** /*out*/ locks, unsigned short count );
static inline void unlock_all( spinlock ** locks, unsigned short count );
static inline void unlock_all( monitor_desc ** locks, unsigned short count );

static inline void save_recursion   ( monitor_desc ** ctx, unsigned int * /*out*/ recursions, unsigned short count );
static inline void restore_recursion( monitor_desc ** ctx, unsigned int * /*in */ recursions, unsigned short count );

static inline void init     ( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria );
static inline void init_push( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria );

static inline thread_desc * check_condition( __condition_criterion_t * );
static inline void brand_condition( condition * );
static inline unsigned short insert_unique( thread_desc ** thrds, unsigned short end, thread_desc * val );

static inline thread_desc * search_entry_queue( __acceptable_t * acceptables, int acc_count, monitor_desc ** monitors, int count );

//-----------------------------------------------------------------------------
// 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_desc ** monitors = mons;        /* Save the targeted monitors                                                          */ \
        unsigned short count = cnt;             /* Save the count to a local variable                                                  */ \
        unsigned int recursions[ count ];       /* Save the current recursion levels to restore them later                             */ \
        spinlock *   locks     [ count ];       /* We need to pass-in an array of locks to BlockInternal                               */ \

//-----------------------------------------------------------------------------
// Enter/Leave routines


extern "C" {
        // Enter single monitor
        static void __enter_monitor_desc( monitor_desc * this, monitor_desc ** group, int group_cnt, void (*func)() ) {
                // Lock the monitor spinlock, lock_yield to reduce contention
                lock_yield( &this->lock DEBUG_CTX2 );
                thread_desc * thrd = this_thread;

                this->accepted_index = -1;
                if( !this->owner ) {
                        // No one has the monitor, just take it
                        set_owner( this, thrd );
                }
                else if( this->owner == thrd) {
                        // We already have the monitor, just not how many times we took it
                        verify( this->recursion > 0 );
                        this->recursion += 1;
                }
                else if( (this->accepted_index = is_accepted( thrd, this, group, group_cnt, func)) >= 0 ) {
                        // Some one was waiting for us, enter
                        set_owner( this, thrd );
                }
                else {
                        // Some one else has the monitor, wait in line for it
                        append( &this->entry_queue, thrd );
                        BlockInternal( &this->lock );

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

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

        // Leave single monitor
        void __leave_monitor_desc( monitor_desc * this ) {
                // Lock the monitor spinlock, lock_yield to reduce contention
                lock_yield( &this->lock DEBUG_CTX2 );

                verifyf( this_thread == this->owner, "Expected owner to be %p, got %p (r: %i)", this_thread, this->owner, this->recursion );

                // 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) {
                        unlock( &this->lock );
                        return;
                }

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

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

                //We need to wake-up the thread
                WakeThread( new_owner );
        }

        // Leave the thread monitor
        // last routine called by a thread.
        // Should never return
        void __leave_thread_monitor( thread_desc * thrd ) {
                monitor_desc * this = &thrd->mon;

                // Lock the monitor now
                lock_yield( &this->lock DEBUG_CTX2 );

                disable_interrupts();

                thrd->cor.state = Halted;

                verifyf( thrd == this->owner, "Expected owner to be %p, got %p (r: %i)", thrd, this->owner, this->recursion );

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

                // If we haven't left the last level of recursion
                // it must mean there is an error
                if( this->recursion != 0) { abortf("Thread internal monitor has unbalanced recursion"); }

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

                // Leave the thread, this will unlock the spinlock
                // Use leave thread instead of BlockInternal which is
                // specialized for this case and supports null new_owner
                LeaveThread( &this->lock, new_owner );

                // Control flow should never reach here!
        }
}

// Enter multiple monitor
// relies on the monitor array being sorted
static inline void enter(monitor_desc ** monitors, int count, void (*func)() ) {
        for(int i = 0; i < count; i++) {
                __enter_monitor_desc( monitors[i], monitors, count, func );
        }

        int acc_idx = monitors[0]->accepted_index;
        if( acc_idx >= 0 && monitors[0]->acceptables[ acc_idx ].run_preaccept ) {
                assert( monitors[0]->pre_accept );
                monitors[0]->pre_accept();
        }
}

// Leave multiple monitor
// relies on the monitor array being sorted
static inline void leave(monitor_desc ** monitors, int count) {
        for(int i = count - 1; i >= 0; i--) {
                __leave_monitor_desc( monitors[i] );
        }
}

// Ctor for monitor guard
// Sorts monitors before entering
void ?{}( monitor_guard_t * this, monitor_desc ** m, int count, void (*func)() ) {
        // Store current array
        this->m = m;
        this->count = count;

        // Sort monitors based on address -> TODO use a sort specialized for small numbers
        qsort(this->m, count);

        // Enter the monitors in order
        enter( this->m, this->count, func );

        // Save previous thread context
        this->prev_mntrs = this_thread->current_monitors;
        this->prev_count = this_thread->current_monitor_count;

        // Update thread context (needed for conditions)
        this_thread->current_monitors      = m;
        this_thread->current_monitor_count = count;
}

// Dtor for monitor guard
void ^?{}( monitor_guard_t * this ) {
        // Leave the monitors in order
        leave( this->m, this->count );

        // Restore thread context
        this_thread->current_monitors      = this->prev_mntrs;
        this_thread->current_monitor_count = this->prev_count;
}

//-----------------------------------------------------------------------------
// Internal scheduling types

void ?{}(__condition_node_t * this, thread_desc * waiting_thread, unsigned short count, uintptr_t user_info ) {
        this->waiting_thread = waiting_thread;
        this->count = count;
        this->next = NULL;
        this->user_info = user_info;
}

void ?{}(__condition_criterion_t * this ) {
        this->ready  = false;
        this->target = NULL;
        this->owner  = NULL;
        this->next   = NULL;
}

void ?{}(__condition_criterion_t * this, monitor_desc * target, __condition_node_t * owner ) {
        this->ready  = false;
        this->target = target;
        this->owner  = owner;
        this->next   = NULL;
}

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

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

        // Create storage for monitor context
        monitor_ctx( this->monitors, this->monitor_count );

        // Create the node specific to this wait operation
        wait_ctx( this_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
        append( &this->blocked, &waiter );

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

        // DON'T unlock, ask the kernel to do it

        // Save monitor state
        save_recursion( monitors, recursions, count );

        // Find the next thread(s) to run
        unsigned short thread_count = 0;
        thread_desc * threads[ count ];
        for(int i = 0; i < count; i++) {
                threads[i] = 0;
        }

        // Remove any duplicate threads
        for( int i = 0; i < count; i++) {
                thread_desc * new_owner = next_thread( monitors[i] );
                thread_count = insert_unique( threads, thread_count, new_owner );
        }

        // Everything is ready to go to sleep
        BlockInternal( locks, count, threads, thread_count );


        // WE WOKE UP


        // We are back, restore the owners and recursions
        lock_all( locks, count );
        restore_recursion( monitors, recursions, count );
        unlock_all( locks, count );
}

bool signal( condition * this ) {
        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
        LIB_DEBUG_DO(
                thread_desc * this_thrd = this_thread;
                if ( this->monitor_count != this_thrd->current_monitor_count ) {
                        abortf( "Signal on condition %p made with different number of monitor(s), expected %i got %i", this, this->monitor_count, this_thrd->current_monitor_count );
                }

                for(int i = 0; i < this->monitor_count; i++) {
                        if ( this->monitors[i] != this_thrd->current_monitors[i] ) {
                                abortf( "Signal on condition %p made with different monitor, expected %p got %i", this, this->monitors[i], this_thrd->current_monitors[i] );
                        }
                }
        );

        unsigned short count = this->monitor_count;

        // Lock all monitors
        lock_all( this->monitors, NULL, 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(int i = 0; i < count; i++) {
                __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 ) {
        if( !this->blocked.head ) { return false; }

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

        // Create storage for monitor context
        monitor_ctx( this->monitors, this->monitor_count );

        // 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( this_thread, 0 )

        //save contexts
        save_recursion( monitors, recursions, count );

        //Find the thread to run
        thread_desc * signallee = pop_head( &this->blocked )->waiting_thread;
        for(int i = 0; i < count; i++) {
                set_owner( monitors[i], signallee );
        }

        //Everything is ready to go to sleep
        BlockInternal( locks, count, &signallee, 1 );


        // WE WOKE UP


        //We are back, restore the owners and recursions
        lock_all( locks, count );
        restore_recursion( monitors, recursions, count );
        unlock_all( locks, count );

        return true;
}

// Access the user_info of the thread waiting at the front of the queue
uintptr_t front( condition * this ) {
        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 this->blocked.head->user_info;
}

//-----------------------------------------------------------------------------
// Internal scheduling
int __accept_internal( unsigned short acc_count, __acceptable_t * acceptables ) {
        thread_desc * thrd = this_thread;

        // Create storage for monitor context
        monitor_ctx( acceptables->monitors, acceptables->count );

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

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

        // Check if the entry queue
        thread_desc * next = search_entry_queue( acceptables, acc_count, monitors, count );

        if( !next ) {
                // Update acceptables on the current monitors
                for(int i = 0; i < count; i++) {
                        monitors[i]->acceptables = acceptables;
                        monitors[i]->acceptable_count = acc_count;
                }
        }

        save_recursion( monitors, recursions, count );

        // Everything is ready to go to sleep
        BlockInternal( locks, count, &next, next ? 1 : 0 );


        //WE WOKE UP


        //We are back, restore the owners and recursions
        lock_all( locks, count );
        restore_recursion( monitors, recursions, count );
        int acc_idx = monitors[0]->accepted_index;
        unlock_all( locks, count );

        return acc_idx;
}

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

static inline void set_owner( monitor_desc * this, thread_desc * owner ) {
        //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 thread_desc * next_thread( monitor_desc * this ) {
        //Check the signaller stack
        __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
                set_owner( this,  urgent->owner->waiting_thread );

                return check_condition( urgent );
        }

        // No signaller thread
        // Get the next thread in the entry_queue
        thread_desc * new_owner = pop_head( &this->entry_queue );
        set_owner( this, new_owner );

        return new_owner;
}

static inline int is_accepted( thread_desc * owner, monitor_desc * this, monitor_desc ** group, int group_cnt, void (*func)() ) {
        __acceptable_t* accs = this->acceptables; // Optim
        int acc_cnt = this->acceptable_count;

        // Check if there are any acceptable functions
        if( !accs ) return -1;

        // 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]->accepted_index;

        // For all acceptable functions check if this is the current function.
        OUT_LOOP:
        for( int i = 0; i < acc_cnt; i++ ) {
                __acceptable_t * acc = &accs[i];

                // if function matches, check the monitors
                if( acc->func == func ) {

                        // If the group count is different then it can't be a match
                        if( acc->count != group_cnt ) return -1;

                        // Check that all the monitors match
                        for( int j = 0; j < group_cnt; j++ ) {
                                // If not a match, check next function
                                if( acc->monitors[j] != group[j] ) continue OUT_LOOP;
                        }

                        // It's a complete match, accept the call
                        return i;
                }
        }

        // No function matched
        return -1;
}

static inline void init( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria ) {
        for(int i = 0; i < count; i++) {
                (&criteria[i]){ monitors[i], waiter };
        }

        waiter->criteria = criteria;
}

static inline void init_push( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria ) {
        for(int i = 0; i < count; i++) {
                (&criteria[i]){ monitors[i], waiter };
                push( &criteria[i].target->signal_stack, &criteria[i] );
        }

        waiter->criteria = criteria;
}

static inline void lock_all( spinlock ** locks, unsigned short count ) {
        for( int i = 0; i < count; i++ ) {
                lock_yield( locks[i] DEBUG_CTX2 );
        }
}

static inline void lock_all( monitor_desc ** source, spinlock ** /*out*/ locks, unsigned short count ) {
        for( int i = 0; i < count; i++ ) {
                spinlock * l = &source[i]->lock;
                lock_yield( l DEBUG_CTX2 );
                if(locks) locks[i] = l;
        }
}

static inline void unlock_all( spinlock ** locks, unsigned short count ) {
        for( int i = 0; i < count; i++ ) {
                unlock( locks[i] );
        }
}

static inline void unlock_all( monitor_desc ** locks, unsigned short count ) {
        for( int i = 0; i < count; i++ ) {
                unlock( &locks[i]->lock );
        }
}


static inline void save_recursion   ( monitor_desc ** ctx, unsigned int * /*out*/ recursions, unsigned short count ) {
        for( int i = 0; i < count; i++ ) {
                recursions[i] = ctx[i]->recursion;
        }
}

static inline void restore_recursion( monitor_desc ** ctx, unsigned int * /*in */ recursions, unsigned short count ) {
        for( int i = 0; i < count; i++ ) {
                ctx[i]->recursion = recursions[i];
        }
}

// 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_desc * 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(    int i = 0; i < count; i++ ) {

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

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

        // LIB_DEBUG_PRINT_SAFE( "Runing %i\n", ready2run );
        return ready2run ? node->waiting_thread : NULL;
}

static inline void brand_condition( condition * this ) {
        thread_desc * thrd = this_thread;
        if( !this->monitors ) {
                // LIB_DEBUG_PRINT_SAFE("Branding\n");
                assertf( thrd->current_monitors != NULL, "No current monitor to brand condition %p", thrd->current_monitors );
                this->monitor_count = thrd->current_monitor_count;

                this->monitors = malloc( this->monitor_count * sizeof( *this->monitors ) );
                for( int i = 0; i < this->monitor_count; i++ ) {
                        this->monitors[i] = thrd->current_monitors[i];
                }
        }
}

static inline unsigned short insert_unique( thread_desc ** thrds, unsigned short end, thread_desc * val ) {
        if( !val ) return end;

        for(int i = 0; i <= end; i++) {
                if( thrds[i] == val ) return end;
        }

        thrds[end] = val;
        return end + 1;
}

static inline thread_desc * search_entry_queue( __acceptable_t * acceptables, int acc_count, monitor_desc ** monitors, int count ) {
        return NULL;
}

void ?{}( __condition_blocked_queue_t * this ) {
        this->head = NULL;
        this->tail = &this->head;
}

void append( __condition_blocked_queue_t * this, __condition_node_t * c ) {
        verify(this->tail != NULL);
        *this->tail = c;
        this->tail = &c->next;
}

__condition_node_t * pop_head( __condition_blocked_queue_t * this ) {
        __condition_node_t * head = this->head;
        if( head ) {
                this->head = head->next;
                if( !head->next ) {
                        this->tail = &this->head;
                }
                head->next = NULL;
        }
        return head;
}

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