source: src/libcfa/concurrency/monitor.c@ 0895cba

ADT aaron-thesis arm-eh ast-experimental cleanup-dtors deferred_resn demangler enum forall-pointer-decay jacob/cs343-translation jenkins-sandbox new-ast new-ast-unique-expr new-env no_list persistent-indexer pthread-emulation qualifiedEnum resolv-new with_gc
Last change on this file since 0895cba was b18830e, checked in by Thierry Delisle <tdelisle@…>, 8 years ago

Refactoring monitor code in prevision for proper waitfor support

  • added monitor group struct
  • else and timeout now return negative results
  • Property mode set to 100644
File size: 22.3 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2016 University of Waterloo
3//
4// The contents of this file are covered under the licence agreement in the
5// file "LICENCE" distributed with Cforall.
6//
7// monitor_desc.c --
8//
9// Author : Thierry Delisle
10// Created On : Thd Feb 23 12:27:26 2017
11// Last Modified By : Peter A. Buhr
12// Last Modified On : Mon Jul 31 14:59:05 2017
13// Update Count : 3
14//
15
16#include "monitor"
17
18#include <stdlib>
19
20#include "libhdr.h"
21#include "kernel_private.h"
22
23//-----------------------------------------------------------------------------
24// Forward declarations
25static inline void set_owner( monitor_desc * this, thread_desc * owner );
26static inline thread_desc * next_thread( monitor_desc * this );
27static inline int is_accepted( thread_desc * owner, monitor_desc * this, const __monitor_group & monitors );
28
29static inline void lock_all( spinlock ** locks, unsigned short count );
30static inline void lock_all( monitor_desc ** source, spinlock ** /*out*/ locks, unsigned short count );
31static inline void unlock_all( spinlock ** locks, unsigned short count );
32static inline void unlock_all( monitor_desc ** locks, unsigned short count );
33
34static inline void save_recursion ( monitor_desc ** ctx, unsigned int * /*out*/ recursions, unsigned short count );
35static inline void restore_recursion( monitor_desc ** ctx, unsigned int * /*in */ recursions, unsigned short count );
36
37static inline void init ( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria );
38static inline void init_push( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria );
39
40static inline thread_desc * check_condition( __condition_criterion_t * );
41static inline void brand_condition( condition * );
42static inline unsigned short insert_unique( thread_desc ** thrds, unsigned short end, thread_desc * val );
43
44static inline [thread_desc *, int] search_entry_queue( __acceptable_t * acceptables, int acc_count, monitor_desc ** monitors, int count );
45
46static inline short count_max( short acc_count, __acceptable_t * acceptables );
47static inline short aggregate( monitor_desc ** storage, short count, __acceptable_t * acceptables );
48static inline void set_mask ( monitor_desc ** storage, short count, __acceptable_t * acceptables, short acc_count );
49
50//-----------------------------------------------------------------------------
51// Useful defines
52#define wait_ctx(thrd, user_info) /* Create the necessary information to use the signaller stack */ \
53 __condition_node_t waiter = { thrd, count, user_info }; /* Create the node specific to this wait operation */ \
54 __condition_criterion_t criteria[count]; /* Create the creteria this wait operation needs to wake up */ \
55 init( count, monitors, &waiter, criteria ); /* Link everything together */ \
56
57#define wait_ctx_primed(thrd, user_info) /* Create the necessary information to use the signaller stack */ \
58 __condition_node_t waiter = { thrd, count, user_info }; /* Create the node specific to this wait operation */ \
59 __condition_criterion_t criteria[count]; /* Create the creteria this wait operation needs to wake up */ \
60 init_push( count, monitors, &waiter, criteria ); /* Link everything together and push it to the AS-Stack */ \
61
62#define monitor_ctx( mons, cnt ) /* Define that create the necessary struct for internal/external scheduling operations */ \
63 monitor_desc ** monitors = mons; /* Save the targeted monitors */ \
64 unsigned short count = cnt; /* Save the count to a local variable */ \
65 unsigned int recursions[ count ]; /* Save the current recursion levels to restore them later */ \
66 spinlock * locks [ count ]; /* We need to pass-in an array of locks to BlockInternal */ \
67
68//-----------------------------------------------------------------------------
69// Enter/Leave routines
70
71
72extern "C" {
73 // Enter single monitor
74 static void __enter_monitor_desc( const __monitor_group & group ) {
75 monitor_desc * this = group.list[0];
76
77 // Lock the monitor spinlock, lock_yield to reduce contention
78 lock_yield( &this->lock DEBUG_CTX2 );
79 thread_desc * thrd = this_thread;
80
81 LIB_DEBUG_PRINT_SAFE("Kernel : %10p Entering mon %p (%p)\n", thrd, this, this->owner);
82
83 this->accepted_index = -1;
84 if( !this->owner ) {
85 // No one has the monitor, just take it
86 set_owner( this, thrd );
87
88 LIB_DEBUG_PRINT_SAFE("Kernel : mon is free \n");
89 }
90 else if( this->owner == thrd) {
91 // We already have the monitor, just not how many times we took it
92 verify( this->recursion > 0 );
93 this->recursion += 1;
94
95 LIB_DEBUG_PRINT_SAFE("Kernel : mon already owned \n");
96 }
97 else if( (this->accepted_index = is_accepted( thrd, this, group)) >= 0 ) {
98 // Some one was waiting for us, enter
99 set_owner( this, thrd );
100
101 LIB_DEBUG_PRINT_SAFE("Kernel : mon accepts \n");
102 }
103 else {
104 LIB_DEBUG_PRINT_SAFE("Kernel : blocking \n");
105
106 // Some one else has the monitor, wait in line for it
107 append( &this->entry_queue, thrd );
108 BlockInternal( &this->lock );
109
110 LIB_DEBUG_PRINT_SAFE("Kernel : %10p Entered mon %p\n", thrd, this);
111
112 // BlockInternal will unlock spinlock, no need to unlock ourselves
113 return;
114 }
115
116 LIB_DEBUG_PRINT_SAFE("Kernel : %10p Entered mon %p\n", thrd, this);
117
118 // Release the lock and leave
119 unlock( &this->lock );
120 return;
121 }
122
123 // Leave single monitor
124 void __leave_monitor_desc( monitor_desc * this ) {
125 // Lock the monitor spinlock, lock_yield to reduce contention
126 lock_yield( &this->lock DEBUG_CTX2 );
127
128 verifyf( this_thread == this->owner, "Expected owner to be %p, got %p (r: %i)", this_thread, this->owner, this->recursion );
129
130 // Leaving a recursion level, decrement the counter
131 this->recursion -= 1;
132
133 // If we haven't left the last level of recursion
134 // it means we don't need to do anything
135 if( this->recursion != 0) {
136 unlock( &this->lock );
137 return;
138 }
139
140 // Get the next thread, will be null on low contention monitor
141 thread_desc * new_owner = next_thread( this );
142
143 // We can now let other threads in safely
144 unlock( &this->lock );
145
146 //We need to wake-up the thread
147 WakeThread( new_owner );
148 }
149
150 // Leave the thread monitor
151 // last routine called by a thread.
152 // Should never return
153 void __leave_thread_monitor( thread_desc * thrd ) {
154 monitor_desc * this = &thrd->self_mon;
155
156 // Lock the monitor now
157 lock_yield( &this->lock DEBUG_CTX2 );
158
159 disable_interrupts();
160
161 thrd->self_cor.state = Halted;
162
163 verifyf( thrd == this->owner, "Expected owner to be %p, got %p (r: %i)", thrd, this->owner, this->recursion );
164
165 // Leaving a recursion level, decrement the counter
166 this->recursion -= 1;
167
168 // If we haven't left the last level of recursion
169 // it must mean there is an error
170 if( this->recursion != 0) { abortf("Thread internal monitor has unbalanced recursion"); }
171
172 // Fetch the next thread, can be null
173 thread_desc * new_owner = next_thread( this );
174
175 // Leave the thread, this will unlock the spinlock
176 // Use leave thread instead of BlockInternal which is
177 // specialized for this case and supports null new_owner
178 LeaveThread( &this->lock, new_owner );
179
180 // Control flow should never reach here!
181 }
182}
183
184// Enter multiple monitor
185// relies on the monitor array being sorted
186static inline void enter( __monitor_group monitors ) {
187 for(int i = 0; i < monitors.size; i++) {
188 __enter_monitor_desc( monitors );
189 }
190}
191
192// Leave multiple monitor
193// relies on the monitor array being sorted
194static inline void leave(monitor_desc ** monitors, int count) {
195 for(int i = count - 1; i >= 0; i--) {
196 __leave_monitor_desc( monitors[i] );
197 }
198}
199
200// Ctor for monitor guard
201// Sorts monitors before entering
202void ?{}( monitor_guard_t & this, monitor_desc ** m, int count, void (*func)() ) {
203 // Store current array
204 this.m = m;
205 this.count = count;
206
207 // Sort monitors based on address -> TODO use a sort specialized for small numbers
208 qsort(this.m, count);
209
210 // Save previous thread context
211 this.prev_mntrs = this_thread->monitors.list;
212 this.prev_count = this_thread->monitors.size;
213 this.prev_func = this_thread->monitors.func;
214
215 // Update thread context (needed for conditions)
216 this_thread->monitors.list = m;
217 this_thread->monitors.size = count;
218 this_thread->monitors.func = func;
219
220 // Enter the monitors in order
221 __monitor_group group = {this.m, this.count, func};
222 enter( group );
223}
224
225
226// Dtor for monitor guard
227void ^?{}( monitor_guard_t & this ) {
228 // Leave the monitors in order
229 leave( this.m, this.count );
230
231 // Restore thread context
232 this_thread->monitors.list = this.prev_mntrs;
233 this_thread->monitors.size = this.prev_count;
234 this_thread->monitors.func = this.prev_func;
235}
236
237//-----------------------------------------------------------------------------
238// Internal scheduling types
239void ?{}(__condition_node_t & this, thread_desc * waiting_thread, unsigned short count, uintptr_t user_info ) {
240 this.waiting_thread = waiting_thread;
241 this.count = count;
242 this.next = NULL;
243 this.user_info = user_info;
244}
245
246void ?{}(__condition_criterion_t & this ) {
247 this.ready = false;
248 this.target = NULL;
249 this.owner = NULL;
250 this.next = NULL;
251}
252
253void ?{}(__condition_criterion_t & this, monitor_desc * target, __condition_node_t * owner ) {
254 this.ready = false;
255 this.target = target;
256 this.owner = owner;
257 this.next = NULL;
258}
259
260//-----------------------------------------------------------------------------
261// Internal scheduling
262void wait( condition * this, uintptr_t user_info = 0 ) {
263 brand_condition( this );
264
265 // Check that everything is as expected
266 assertf( this->monitors != NULL, "Waiting with no monitors (%p)", this->monitors );
267 verifyf( this->monitor_count != 0, "Waiting with 0 monitors (%i)", this->monitor_count );
268 verifyf( this->monitor_count < 32u, "Excessive monitor count (%i)", this->monitor_count );
269
270 // Create storage for monitor context
271 monitor_ctx( this->monitors, this->monitor_count );
272
273 // Create the node specific to this wait operation
274 wait_ctx( this_thread, user_info );
275
276 // Append the current wait operation to the ones already queued on the condition
277 // We don't need locks for that since conditions must always be waited on inside monitor mutual exclusion
278 append( &this->blocked, &waiter );
279
280 // Lock all monitors (aggregates the lock them as well)
281 lock_all( monitors, locks, count );
282
283 // DON'T unlock, ask the kernel to do it
284
285 // Save monitor state
286 save_recursion( monitors, recursions, count );
287
288 // Find the next thread(s) to run
289 unsigned short thread_count = 0;
290 thread_desc * threads[ count ];
291 for(int i = 0; i < count; i++) {
292 threads[i] = 0;
293 }
294
295 // Remove any duplicate threads
296 for( int i = 0; i < count; i++) {
297 thread_desc * new_owner = next_thread( monitors[i] );
298 thread_count = insert_unique( threads, thread_count, new_owner );
299 }
300
301 // Everything is ready to go to sleep
302 BlockInternal( locks, count, threads, thread_count );
303
304
305 // WE WOKE UP
306
307
308 // We are back, restore the owners and recursions
309 lock_all( locks, count );
310 restore_recursion( monitors, recursions, count );
311 unlock_all( locks, count );
312}
313
314bool signal( condition * this ) {
315 if( is_empty( this ) ) { return false; }
316
317 //Check that everything is as expected
318 verify( this->monitors );
319 verify( this->monitor_count != 0 );
320
321 //Some more checking in debug
322 LIB_DEBUG_DO(
323 thread_desc * this_thrd = this_thread;
324 if ( this->monitor_count != this_thrd->monitors.size ) {
325 abortf( "Signal on condition %p made with different number of monitor(s), expected %i got %i", this, this->monitor_count, this_thrd->monitors.size );
326 }
327
328 for(int i = 0; i < this->monitor_count; i++) {
329 if ( this->monitors[i] != this_thrd->monitors.list[i] ) {
330 abortf( "Signal on condition %p made with different monitor, expected %p got %i", this, this->monitors[i], this_thrd->monitors.list[i] );
331 }
332 }
333 );
334
335 unsigned short count = this->monitor_count;
336
337 // Lock all monitors
338 lock_all( this->monitors, NULL, count );
339
340 //Pop the head of the waiting queue
341 __condition_node_t * node = pop_head( &this->blocked );
342
343 //Add the thread to the proper AS stack
344 for(int i = 0; i < count; i++) {
345 __condition_criterion_t * crit = &node->criteria[i];
346 assert( !crit->ready );
347 push( &crit->target->signal_stack, crit );
348 }
349
350 //Release
351 unlock_all( this->monitors, count );
352
353 return true;
354}
355
356bool signal_block( condition * this ) {
357 if( !this->blocked.head ) { return false; }
358
359 //Check that everything is as expected
360 verifyf( this->monitors != NULL, "Waiting with no monitors (%p)", this->monitors );
361 verifyf( this->monitor_count != 0, "Waiting with 0 monitors (%i)", this->monitor_count );
362
363 // Create storage for monitor context
364 monitor_ctx( this->monitors, this->monitor_count );
365
366 // Lock all monitors (aggregates the locks them as well)
367 lock_all( monitors, locks, count );
368
369 // Create the node specific to this wait operation
370 wait_ctx_primed( this_thread, 0 )
371
372 //save contexts
373 save_recursion( monitors, recursions, count );
374
375 //Find the thread to run
376 thread_desc * signallee = pop_head( &this->blocked )->waiting_thread;
377 for(int i = 0; i < count; i++) {
378 set_owner( monitors[i], signallee );
379 }
380
381 //Everything is ready to go to sleep
382 BlockInternal( locks, count, &signallee, 1 );
383
384
385 // WE WOKE UP
386
387
388 //We are back, restore the owners and recursions
389 lock_all( locks, count );
390 restore_recursion( monitors, recursions, count );
391 unlock_all( locks, count );
392
393 return true;
394}
395
396// Access the user_info of the thread waiting at the front of the queue
397uintptr_t front( condition * this ) {
398 verifyf( !is_empty(this),
399 "Attempt to access user data on an empty condition.\n"
400 "Possible cause is not checking if the condition is empty before reading stored data."
401 );
402 return this->blocked.head->user_info;
403}
404
405//-----------------------------------------------------------------------------
406// External scheduling
407// cases to handle :
408// - target already there :
409// block and wake
410// - dtor already there
411// put thread on signaller stack
412// - non-blocking
413// return else
414// - timeout
415// return timeout
416// - block
417// setup mask
418// block
419int __waitfor_internal( unsigned short acc_count, __acceptable_t * acceptables, int duration ) {
420 // This statment doesn't have a contiguous list of monitors...
421 // Create one!
422 short max = count_max( acc_count, acceptables );
423 monitor_desc * mon_storage[max];
424 short actual_count = aggregate( mon_storage, acc_count, acceptables );
425
426 // Create storage for monitor context
427 monitor_ctx( mon_storage, actual_count );
428
429 // Lock all monitors (aggregates the lock them as well)
430 lock_all( monitors, locks, count );
431
432 {
433 // Check if the entry queue
434 thread_desc * next;
435 int index;
436 [next, index] = search_entry_queue( acceptables, acc_count, monitors, count );
437
438 if( next ) {
439 if( acceptables[index].is_dtor ) {
440 #warning case not implemented
441 }
442 else {
443 save_recursion( monitors, recursions, count );
444
445 // Everything is ready to go to sleep
446 BlockInternal( locks, count, &next, 1 );
447
448
449 //WE WOKE UP
450
451
452 //We are back, restore the owners and recursions
453 lock_all( locks, count );
454 restore_recursion( monitors, recursions, count );
455 unlock_all( locks, count );
456 }
457
458 return index;
459 }
460 }
461
462
463 if( duration == 0 ) return -1;
464
465 set_mask( monitors, count, acceptables, acc_count );
466
467 verifyf( duration < 0, "Timeout on waitfor statments not supported yet.");
468
469
470 save_recursion( monitors, recursions, count );
471
472
473 // Everything is ready to go to sleep
474 BlockInternal( locks, count );
475
476
477 //WE WOKE UP
478
479
480 //We are back, restore the owners and recursions
481 lock_all( locks, count );
482 restore_recursion( monitors, recursions, count );
483 int acc_idx = monitors[0]->accepted_index;
484 unlock_all( locks, count );
485
486 return acc_idx;
487}
488
489//-----------------------------------------------------------------------------
490// Utilities
491
492static inline void set_owner( monitor_desc * this, thread_desc * owner ) {
493 //Pass the monitor appropriately
494 this->owner = owner;
495
496 //We are passing the monitor to someone else, which means recursion level is not 0
497 this->recursion = owner ? 1 : 0;
498}
499
500static inline thread_desc * next_thread( monitor_desc * this ) {
501 //Check the signaller stack
502 __condition_criterion_t * urgent = pop( &this->signal_stack );
503 if( urgent ) {
504 //The signaller stack is not empty,
505 //regardless of if we are ready to baton pass,
506 //we need to set the monitor as in use
507 set_owner( this, urgent->owner->waiting_thread );
508
509 return check_condition( urgent );
510 }
511
512 // No signaller thread
513 // Get the next thread in the entry_queue
514 thread_desc * new_owner = pop_head( &this->entry_queue );
515 set_owner( this, new_owner );
516
517 return new_owner;
518}
519
520static inline void init( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria ) {
521 for(int i = 0; i < count; i++) {
522 (criteria[i]){ monitors[i], waiter };
523 }
524
525 waiter->criteria = criteria;
526}
527
528static inline void init_push( int count, monitor_desc ** monitors, __condition_node_t * waiter, __condition_criterion_t * criteria ) {
529 for(int i = 0; i < count; i++) {
530 (criteria[i]){ monitors[i], waiter };
531 push( &criteria[i].target->signal_stack, &criteria[i] );
532 }
533
534 waiter->criteria = criteria;
535}
536
537static inline void lock_all( spinlock ** locks, unsigned short count ) {
538 for( int i = 0; i < count; i++ ) {
539 lock_yield( locks[i] DEBUG_CTX2 );
540 }
541}
542
543static inline void lock_all( monitor_desc ** source, spinlock ** /*out*/ locks, unsigned short count ) {
544 for( int i = 0; i < count; i++ ) {
545 spinlock * l = &source[i]->lock;
546 lock_yield( l DEBUG_CTX2 );
547 if(locks) locks[i] = l;
548 }
549}
550
551static inline void unlock_all( spinlock ** locks, unsigned short count ) {
552 for( int i = 0; i < count; i++ ) {
553 unlock( locks[i] );
554 }
555}
556
557static inline void unlock_all( monitor_desc ** locks, unsigned short count ) {
558 for( int i = 0; i < count; i++ ) {
559 unlock( &locks[i]->lock );
560 }
561}
562
563
564static inline void save_recursion ( monitor_desc ** ctx, unsigned int * /*out*/ recursions, unsigned short count ) {
565 for( int i = 0; i < count; i++ ) {
566 recursions[i] = ctx[i]->recursion;
567 }
568}
569
570static inline void restore_recursion( monitor_desc ** ctx, unsigned int * /*in */ recursions, unsigned short count ) {
571 for( int i = 0; i < count; i++ ) {
572 ctx[i]->recursion = recursions[i];
573 }
574}
575
576// Function has 2 different behavior
577// 1 - Marks a monitors as being ready to run
578// 2 - Checks if all the monitors are ready to run
579// if so return the thread to run
580static inline thread_desc * check_condition( __condition_criterion_t * target ) {
581 __condition_node_t * node = target->owner;
582 unsigned short count = node->count;
583 __condition_criterion_t * criteria = node->criteria;
584
585 bool ready2run = true;
586
587 for( int i = 0; i < count; i++ ) {
588
589 // LIB_DEBUG_PRINT_SAFE( "Checking %p for %p\n", &criteria[i], target );
590 if( &criteria[i] == target ) {
591 criteria[i].ready = true;
592 // LIB_DEBUG_PRINT_SAFE( "True\n" );
593 }
594
595 ready2run = criteria[i].ready && ready2run;
596 }
597
598 // LIB_DEBUG_PRINT_SAFE( "Runing %i\n", ready2run );
599 return ready2run ? node->waiting_thread : NULL;
600}
601
602static inline void brand_condition( condition * this ) {
603 thread_desc * thrd = this_thread;
604 if( !this->monitors ) {
605 // LIB_DEBUG_PRINT_SAFE("Branding\n");
606 assertf( thrd->monitors.list != NULL, "No current monitor to brand condition %p", thrd->monitors.list );
607 this->monitor_count = thrd->monitors.size;
608
609 this->monitors = malloc( this->monitor_count * sizeof( *this->monitors ) );
610 for( int i = 0; i < this->monitor_count; i++ ) {
611 this->monitors[i] = thrd->monitors.list[i];
612 }
613 }
614}
615
616static inline unsigned short insert_unique( thread_desc ** thrds, unsigned short end, thread_desc * val ) {
617 if( !val ) return end;
618
619 for(int i = 0; i <= end; i++) {
620 if( thrds[i] == val ) return end;
621 }
622
623 thrds[end] = val;
624 return end + 1;
625}
626
627static inline int is_accepted( thread_desc * owner, monitor_desc * this, const __monitor_group & group ) {
628 __acceptable_t* accs = this->acceptables; // Optim
629 int acc_cnt = this->acceptable_count;
630
631 // Check if there are any acceptable functions
632 if( !accs ) return -1;
633
634 // If this isn't the first monitor to test this, there is no reason to repeat the test.
635 if( this != group[0] ) return group[0]->accepted_index;
636
637 // For all acceptable functions check if this is the current function.
638 for( int i = 0; i < acc_cnt; i++ ) {
639 __acceptable_t * acc = &accs[i];
640
641 if( acc->monitors == group ) return i;
642 }
643
644 // No function matched
645 return -1;
646}
647
648static inline [thread_desc *, int] search_entry_queue( __acceptable_t * acceptables, int acc_count, monitor_desc ** monitors, int count ) {
649
650 __thread_queue_t * entry_queue = &monitors[0]->entry_queue;
651
652 // For each thread in the entry-queue
653 for( thread_desc ** thrd_it = &entry_queue->head;
654 *thrd_it;
655 thrd_it = &(*thrd_it)->next)
656 {
657 // For each acceptable check if it matches
658 int i;
659 __acceptable_t * acc_end = acceptables + acc_count;
660 for( __acceptable_t * acc_it = acceptables; acc_it != acc_end; acc_it++, i++ ) {
661 // Check if we have a match
662 if( acc_it->monitors == (*thrd_it)->monitors ) {
663
664 // If we have a match return it
665 // after removeing it from the entry queue
666 return [remove( entry_queue, thrd_it ), i];
667 }
668 }
669 }
670
671 return [0, -1];
672}
673
674static inline short count_max( short acc_count, __acceptable_t * acceptables ) {
675 short max = 0;
676 for( int i = 0; i < acc_count; i++ ) {
677 max += acceptables[i].monitors.size;
678 }
679 return max;
680}
681
682static inline short aggregate( monitor_desc ** storage, short count, __acceptable_t * acceptables ) {
683 #warning function not implemented
684 return 0;
685}
686
687static inline void set_mask( monitor_desc ** storage, short count, __acceptable_t * acceptables, short acc_count ) {
688 for(int i = 0; i < count; i++) {
689 storage[i]->acceptables = acceptables;
690 storage[i]->acceptable_count = acc_count;
691 storage[i]->accepted_index = -1;
692 }
693}
694
695
696void ?{}( __condition_blocked_queue_t & this ) {
697 this.head = NULL;
698 this.tail = &this.head;
699}
700
701void append( __condition_blocked_queue_t * this, __condition_node_t * c ) {
702 verify(this->tail != NULL);
703 *this->tail = c;
704 this->tail = &c->next;
705}
706
707__condition_node_t * pop_head( __condition_blocked_queue_t * this ) {
708 __condition_node_t * head = this->head;
709 if( head ) {
710 this->head = head->next;
711 if( !head->next ) {
712 this->tail = &this->head;
713 }
714 head->next = NULL;
715 }
716 return head;
717}
718
719// Local Variables: //
720// mode: c //
721// tab-width: 4 //
722// End: //
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