source: libcfa/src/concurrency/kernel.cfa@ e699eb6

ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast new-ast-unique-expr pthread-emulation qualifiedEnum
Last change on this file since e699eb6 was 1eb239e4, checked in by Thierry Delisle <tdelisle@…>, 5 years ago

Removed snzi and replaced it with a fast/slow path
  • Property mode set to 100644
File size: 22.0 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// kernel.c --
8//
9// Author : Thierry Delisle
10// Created On : Tue Jan 17 12:27:26 2017
11// Last Modified By : Peter A. Buhr
12// Last Modified On : Thu Jul 9 06:22:54 2020
13// Update Count : 66
14//
15
16#define __cforall_thread__
17// #define __CFA_DEBUG_PRINT_RUNTIME_CORE__
18
19//C Includes
20#include <errno.h>
21#include <stdio.h>
22#include <signal.h>
23#include <unistd.h>
24
25//CFA Includes
26#include "kernel_private.hfa"
27#include "preemption.hfa"
28
29//Private includes
30#define __CFA_INVOKE_PRIVATE__
31#include "invoke.h"
32
33
34//-----------------------------------------------------------------------------
35// Some assembly required
36#if defined( __i386 )
37 // mxcr : SSE Status and Control bits (control bits are preserved across function calls)
38 // fcw : X87 FPU control word (preserved across function calls)
39 #define __x87_store \
40 uint32_t __mxcr; \
41 uint16_t __fcw; \
42 __asm__ volatile ( \
43 "stmxcsr %0\n" \
44 "fnstcw %1\n" \
45 : "=m" (__mxcr),\
46 "=m" (__fcw) \
47 )
48
49 #define __x87_load \
50 __asm__ volatile ( \
51 "fldcw %1\n" \
52 "ldmxcsr %0\n" \
53 ::"m" (__mxcr),\
54 "m" (__fcw) \
55 )
56
57#elif defined( __x86_64 )
58 #define __x87_store \
59 uint32_t __mxcr; \
60 uint16_t __fcw; \
61 __asm__ volatile ( \
62 "stmxcsr %0\n" \
63 "fnstcw %1\n" \
64 : "=m" (__mxcr),\
65 "=m" (__fcw) \
66 )
67
68 #define __x87_load \
69 __asm__ volatile ( \
70 "fldcw %1\n" \
71 "ldmxcsr %0\n" \
72 :: "m" (__mxcr),\
73 "m" (__fcw) \
74 )
75
76
77#elif defined( __ARM_ARCH )
78#else
79 #error unknown hardware architecture
80#endif
81
82extern $thread * mainThread;
83extern processor * mainProcessor;
84
85//-----------------------------------------------------------------------------
86// Kernel Scheduling logic
87static $thread * __next_thread(cluster * this);
88static $thread * __next_thread_slow(cluster * this);
89static void __run_thread(processor * this, $thread * dst);
90static void __wake_one(struct __processor_id_t * id, cluster * cltr);
91
92static void push (__cluster_idles & idles, processor & proc);
93static void remove(__cluster_idles & idles, processor & proc);
94static [unsigned idle, unsigned total, * processor] query( & __cluster_idles idles );
95
96
97//=============================================================================================
98// Kernel Scheduling logic
99//=============================================================================================
100//Main of the processor contexts
101void main(processorCtx_t & runner) {
102 // Because of a bug, we couldn't initialized the seed on construction
103 // Do it here
104 kernelTLS.rand_seed ^= rdtscl();
105
106 processor * this = runner.proc;
107 verify(this);
108
109 __cfadbg_print_safe(runtime_core, "Kernel : core %p starting\n", this);
110 #if !defined(__CFA_NO_STATISTICS__)
111 if( this->print_halts ) {
112 __cfaabi_bits_print_safe( STDOUT_FILENO, "Processor : %d - %s (%p)\n", this->id, this->name, (void*)this);
113 }
114 #endif
115
116 {
117 // Setup preemption data
118 preemption_scope scope = { this };
119
120 __cfadbg_print_safe(runtime_core, "Kernel : core %p started\n", this);
121
122 $thread * readyThread = 0p;
123 MAIN_LOOP:
124 for() {
125 // Try to get the next thread
126 readyThread = __next_thread( this->cltr );
127
128 if( !readyThread ) {
129 readyThread = __next_thread_slow( this->cltr );
130 }
131
132 HALT:
133 if( !readyThread ) {
134 // Don't block if we are done
135 if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
136
137 #if !defined(__CFA_NO_STATISTICS__)
138 __tls_stats()->ready.sleep.halts++;
139 #endif
140
141 // Push self to idle stack
142 push(this->cltr->idles, * this);
143
144 // Confirm the ready-queue is empty
145 readyThread = __next_thread_slow( this->cltr );
146 if( readyThread ) {
147 // A thread was found, cancel the halt
148 remove(this->cltr->idles, * this);
149
150 #if !defined(__CFA_NO_STATISTICS__)
151 __tls_stats()->ready.sleep.cancels++;
152 #endif
153
154 // continue the mai loop
155 break HALT;
156 }
157
158 #if !defined(__CFA_NO_STATISTICS__)
159 if(this->print_halts) {
160 __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 0\n", this->id, rdtscl());
161 }
162 #endif
163
164 wait( this->idle );
165
166 #if !defined(__CFA_NO_STATISTICS__)
167 if(this->print_halts) {
168 __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 1\n", this->id, rdtscl());
169 }
170 #endif
171
172 // We were woken up, remove self from idle
173 remove(this->cltr->idles, * this);
174
175 // DON'T just proceed, start looking again
176 continue MAIN_LOOP;
177 }
178
179 /* paranoid */ verify( readyThread );
180
181 // We found a thread run it
182 __run_thread(this, readyThread);
183
184 // Are we done?
185 if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
186 }
187
188 __cfadbg_print_safe(runtime_core, "Kernel : core %p stopping\n", this);
189 }
190
191 V( this->terminated );
192
193 if(this == mainProcessor) {
194 // HACK : the coroutine context switch expects this_thread to be set
195 // and it make sense for it to be set in all other cases except here
196 // fake it
197 kernelTLS.this_thread = mainThread;
198 }
199
200 __cfadbg_print_safe(runtime_core, "Kernel : core %p terminated\n", this);
201}
202
203static int * __volatile_errno() __attribute__((noinline));
204static int * __volatile_errno() { asm(""); return &errno; }
205
206// KERNEL ONLY
207// runThread runs a thread by context switching
208// from the processor coroutine to the target thread
209static void __run_thread(processor * this, $thread * thrd_dst) {
210 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
211 /* paranoid */ verifyf( thrd_dst->state == Ready || thrd_dst->preempted != __NO_PREEMPTION, "state : %d, preempted %d\n", thrd_dst->state, thrd_dst->preempted);
212 /* paranoid */ verifyf( thrd_dst->link.next == 0p, "Expected null got %p", thrd_dst->link.next );
213 __builtin_prefetch( thrd_dst->context.SP );
214
215 $coroutine * proc_cor = get_coroutine(this->runner);
216
217 // Update global state
218 kernelTLS.this_thread = thrd_dst;
219
220 // set state of processor coroutine to inactive
221 verify(proc_cor->state == Active);
222 proc_cor->state = Blocked;
223
224 // Actually run the thread
225 RUNNING: while(true) {
226 thrd_dst->preempted = __NO_PREEMPTION;
227 thrd_dst->state = Active;
228
229 __cfaabi_dbg_debug_do(
230 thrd_dst->park_stale = true;
231 thrd_dst->unpark_stale = true;
232 )
233
234 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
235 /* paranoid */ verify( kernelTLS.this_thread == thrd_dst );
236 /* paranoid */ verifyf( ((uintptr_t)thrd_dst->context.SP) < ((uintptr_t)__get_stack(thrd_dst->curr_cor)->base ) || thrd_dst->curr_cor == proc_cor, "ERROR : Destination $thread %p has been corrupted.\n StackPointer too small.\n", thrd_dst ); // add escape condition if we are setting up the processor
237 /* paranoid */ verifyf( ((uintptr_t)thrd_dst->context.SP) > ((uintptr_t)__get_stack(thrd_dst->curr_cor)->limit) || thrd_dst->curr_cor == proc_cor, "ERROR : Destination $thread %p has been corrupted.\n StackPointer too large.\n", thrd_dst ); // add escape condition if we are setting up the processor
238
239 // set context switch to the thread that the processor is executing
240 verify( thrd_dst->context.SP );
241 __cfactx_switch( &proc_cor->context, &thrd_dst->context );
242 // when __cfactx_switch returns we are back in the processor coroutine
243
244 /* paranoid */ verifyf( ((uintptr_t)thrd_dst->context.SP) > ((uintptr_t)__get_stack(thrd_dst->curr_cor)->limit), "ERROR : Destination $thread %p has been corrupted.\n StackPointer too large.\n", thrd_dst );
245 /* paranoid */ verifyf( ((uintptr_t)thrd_dst->context.SP) < ((uintptr_t)__get_stack(thrd_dst->curr_cor)->base ), "ERROR : Destination $thread %p has been corrupted.\n StackPointer too small.\n", thrd_dst );
246 /* paranoid */ verify( kernelTLS.this_thread == thrd_dst );
247 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
248
249
250 // We just finished running a thread, there are a few things that could have happened.
251 // 1 - Regular case : the thread has blocked and now one has scheduled it yet.
252 // 2 - Racy case : the thread has blocked but someone has already tried to schedule it.
253 // 4 - Preempted
254 // In case 1, we may have won a race so we can't write to the state again.
255 // In case 2, we lost the race so we now own the thread.
256
257 if(unlikely(thrd_dst->preempted != __NO_PREEMPTION)) {
258 // The thread was preempted, reschedule it and reset the flag
259 __schedule_thread( (__processor_id_t*)this, thrd_dst );
260 break RUNNING;
261 }
262
263 if(unlikely(thrd_dst->state == Halted)) {
264 // The thread has halted, it should never be scheduled/run again
265 // We may need to wake someone up here since
266 unpark( this->destroyer __cfaabi_dbg_ctx2 );
267 this->destroyer = 0p;
268 break RUNNING;
269 }
270
271 /* paranoid */ verify( thrd_dst->state == Active );
272 thrd_dst->state = Blocked;
273
274 // set state of processor coroutine to active and the thread to inactive
275 int old_ticket = __atomic_fetch_sub(&thrd_dst->ticket, 1, __ATOMIC_SEQ_CST);
276 __cfaabi_dbg_debug_do( thrd_dst->park_result = old_ticket; )
277 switch(old_ticket) {
278 case 1:
279 // This is case 1, the regular case, nothing more is needed
280 break RUNNING;
281 case 2:
282 // This is case 2, the racy case, someone tried to run this thread before it finished blocking
283 // In this case, just run it again.
284 continue RUNNING;
285 default:
286 // This makes no sense, something is wrong abort
287 abort();
288 }
289 }
290
291 // Just before returning to the processor, set the processor coroutine to active
292 proc_cor->state = Active;
293 kernelTLS.this_thread = 0p;
294
295 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
296}
297
298// KERNEL_ONLY
299void returnToKernel() {
300 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
301 $coroutine * proc_cor = get_coroutine(kernelTLS.this_processor->runner);
302 $thread * thrd_src = kernelTLS.this_thread;
303
304 #if !defined(__CFA_NO_STATISTICS__)
305 struct processor * last_proc = kernelTLS.this_processor;
306 #endif
307
308 // Run the thread on this processor
309 {
310 int local_errno = *__volatile_errno();
311 #if defined( __i386 ) || defined( __x86_64 )
312 __x87_store;
313 #endif
314 verify( proc_cor->context.SP );
315 __cfactx_switch( &thrd_src->context, &proc_cor->context );
316 #if defined( __i386 ) || defined( __x86_64 )
317 __x87_load;
318 #endif
319 *__volatile_errno() = local_errno;
320 }
321
322 #if !defined(__CFA_NO_STATISTICS__)
323 if(last_proc != kernelTLS.this_processor) {
324 __tls_stats()->ready.threads.migration++;
325 }
326 #endif
327
328 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
329 /* paranoid */ verifyf( ((uintptr_t)thrd_src->context.SP) < ((uintptr_t)__get_stack(thrd_src->curr_cor)->base ), "ERROR : Returning $thread %p has been corrupted.\n StackPointer too small.\n", thrd_src );
330 /* paranoid */ verifyf( ((uintptr_t)thrd_src->context.SP) > ((uintptr_t)__get_stack(thrd_src->curr_cor)->limit), "ERROR : Returning $thread %p has been corrupted.\n StackPointer too large.\n", thrd_src );
331}
332
333//-----------------------------------------------------------------------------
334// Scheduler routines
335// KERNEL ONLY
336void __schedule_thread( struct __processor_id_t * id, $thread * thrd ) {
337 /* paranoid */ verify( thrd );
338 /* paranoid */ verify( thrd->state != Halted );
339 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
340 /* paranoid */ #if defined( __CFA_WITH_VERIFY__ )
341 /* paranoid */ if( thrd->state == Blocked || thrd->state == Start ) assertf( thrd->preempted == __NO_PREEMPTION,
342 "Error inactive thread marked as preempted, state %d, preemption %d\n", thrd->state, thrd->preempted );
343 /* paranoid */ if( thrd->preempted != __NO_PREEMPTION ) assertf(thrd->state == Active,
344 "Error preempted thread marked as not currently running, state %d, preemption %d\n", thrd->state, thrd->preempted );
345 /* paranoid */ #endif
346 /* paranoid */ verifyf( thrd->link.next == 0p, "Expected null got %p", thrd->link.next );
347
348 if (thrd->preempted == __NO_PREEMPTION) thrd->state = Ready;
349
350 ready_schedule_lock ( id );
351 push( thrd->curr_cluster, thrd );
352 __wake_one(id, thrd->curr_cluster);
353 ready_schedule_unlock( id );
354
355 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
356}
357
358// KERNEL ONLY
359static inline $thread * __next_thread(cluster * this) with( *this ) {
360 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
361
362 ready_schedule_lock ( (__processor_id_t*)kernelTLS.this_processor );
363 $thread * thrd = pop( this );
364 ready_schedule_unlock( (__processor_id_t*)kernelTLS.this_processor );
365
366 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
367 return thrd;
368}
369
370// KERNEL ONLY
371static inline $thread * __next_thread_slow(cluster * this) with( *this ) {
372 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
373
374 ready_schedule_lock ( (__processor_id_t*)kernelTLS.this_processor );
375 $thread * thrd = pop_slow( this );
376 ready_schedule_unlock( (__processor_id_t*)kernelTLS.this_processor );
377
378 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
379 return thrd;
380}
381
382// KERNEL ONLY unpark with out disabling interrupts
383void __unpark( struct __processor_id_t * id, $thread * thrd __cfaabi_dbg_ctx_param2 ) {
384 // record activity
385 __cfaabi_dbg_record_thrd( *thrd, false, caller );
386
387 int old_ticket = __atomic_fetch_add(&thrd->ticket, 1, __ATOMIC_SEQ_CST);
388 __cfaabi_dbg_debug_do( thrd->unpark_result = old_ticket; thrd->unpark_state = thrd->state; )
389 switch(old_ticket) {
390 case 1:
391 // Wake won the race, the thread will reschedule/rerun itself
392 break;
393 case 0:
394 /* paranoid */ verify( ! thrd->preempted != __NO_PREEMPTION );
395 /* paranoid */ verify( thrd->state == Blocked );
396
397 // Wake lost the race,
398 __schedule_thread( id, thrd );
399 break;
400 default:
401 // This makes no sense, something is wrong abort
402 abort();
403 }
404}
405
406void unpark( $thread * thrd __cfaabi_dbg_ctx_param2 ) {
407 if( !thrd ) return;
408
409 disable_interrupts();
410 __unpark( (__processor_id_t*)kernelTLS.this_processor, thrd __cfaabi_dbg_ctx_fwd2 );
411 enable_interrupts( __cfaabi_dbg_ctx );
412}
413
414void park( __cfaabi_dbg_ctx_param ) {
415 /* paranoid */ verify( kernelTLS.preemption_state.enabled );
416 disable_interrupts();
417 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
418 /* paranoid */ verify( kernelTLS.this_thread->preempted == __NO_PREEMPTION );
419
420 // record activity
421 __cfaabi_dbg_record_thrd( *kernelTLS.this_thread, true, caller );
422
423 returnToKernel();
424
425 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
426 enable_interrupts( __cfaabi_dbg_ctx );
427 /* paranoid */ verify( kernelTLS.preemption_state.enabled );
428
429}
430
431// KERNEL ONLY
432void __leave_thread() {
433 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
434 returnToKernel();
435 abort();
436}
437
438// KERNEL ONLY
439bool force_yield( __Preemption_Reason reason ) {
440 /* paranoid */ verify( kernelTLS.preemption_state.enabled );
441 disable_interrupts();
442 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
443
444 $thread * thrd = kernelTLS.this_thread;
445 /* paranoid */ verify(thrd->state == Active);
446
447 // SKULLDUGGERY: It is possible that we are preempting this thread just before
448 // it was going to park itself. If that is the case and it is already using the
449 // intrusive fields then we can't use them to preempt the thread
450 // If that is the case, abandon the preemption.
451 bool preempted = false;
452 if(thrd->link.next == 0p) {
453 preempted = true;
454 thrd->preempted = reason;
455 returnToKernel();
456 }
457
458 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
459 enable_interrupts_noPoll();
460 /* paranoid */ verify( kernelTLS.preemption_state.enabled );
461
462 return preempted;
463}
464
465//=============================================================================================
466// Kernel Idle Sleep
467//=============================================================================================
468// Wake a thread from the front if there are any
469static void __wake_one(struct __processor_id_t * id, cluster * this) {
470 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
471 /* paranoid */ verify( ready_schedule_islocked( id ) );
472
473 // Check if there is a sleeping processor
474 processor * p;
475 unsigned idle;
476 unsigned total;
477 [idle, total, p] = query(this->idles);
478
479 // If no one is sleeping, we are done
480 if( idle == 0 ) return;
481
482 // We found a processor, wake it up
483 post( p->idle );
484
485 #if !defined(__CFA_NO_STATISTICS__)
486 __tls_stats()->ready.sleep.wakes++;
487 #endif
488
489 /* paranoid */ verify( ready_schedule_islocked( id ) );
490 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
491
492 return;
493}
494
495// Unconditionnaly wake a thread
496void __wake_proc(processor * this) {
497 __cfadbg_print_safe(runtime_core, "Kernel : waking Processor %p\n", this);
498
499 disable_interrupts();
500 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
501 bool ret = post( this->idle );
502 enable_interrupts( __cfaabi_dbg_ctx );
503}
504
505static void push (__cluster_idles & this, processor & proc) {
506 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
507 lock( this );
508 this.idle++;
509 /* paranoid */ verify( this.idle <= this.total );
510
511 insert_first(this.list, proc);
512 unlock( this );
513 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
514}
515
516static void remove(__cluster_idles & this, processor & proc) {
517 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
518 lock( this );
519 this.idle--;
520 /* paranoid */ verify( this.idle >= 0 );
521
522 remove(proc);
523 unlock( this );
524 /* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
525}
526
527static [unsigned idle, unsigned total, * processor] query( & __cluster_idles this ) {
528 for() {
529 uint64_t l = __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST);
530 if( 1 == (l % 2) ) { Pause(); continue; }
531 unsigned idle = this.idle;
532 unsigned total = this.total;
533 processor * proc = &this.list`first;
534 if(l != __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST)) { Pause(); continue; }
535 return [idle, total, proc];
536 }
537}
538
539//=============================================================================================
540// Unexpected Terminating logic
541//=============================================================================================
542static __spinlock_t kernel_abort_lock;
543static bool kernel_abort_called = false;
544
545void * kernel_abort(void) __attribute__ ((__nothrow__)) {
546 // abort cannot be recursively entered by the same or different processors because all signal handlers return when
547 // the globalAbort flag is true.
548 lock( kernel_abort_lock __cfaabi_dbg_ctx2 );
549
550 // first task to abort ?
551 if ( kernel_abort_called ) { // not first task to abort ?
552 unlock( kernel_abort_lock );
553
554 sigset_t mask;
555 sigemptyset( &mask );
556 sigaddset( &mask, SIGALRM ); // block SIGALRM signals
557 sigaddset( &mask, SIGUSR1 ); // block SIGALRM signals
558 sigsuspend( &mask ); // block the processor to prevent further damage during abort
559 _exit( EXIT_FAILURE ); // if processor unblocks before it is killed, terminate it
560 }
561 else {
562 kernel_abort_called = true;
563 unlock( kernel_abort_lock );
564 }
565
566 return kernelTLS.this_thread;
567}
568
569void kernel_abort_msg( void * kernel_data, char * abort_text, int abort_text_size ) {
570 $thread * thrd = ( $thread * ) kernel_data;
571
572 if(thrd) {
573 int len = snprintf( abort_text, abort_text_size, "Error occurred while executing thread %.256s (%p)", thrd->self_cor.name, thrd );
574 __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
575
576 if ( &thrd->self_cor != thrd->curr_cor ) {
577 len = snprintf( abort_text, abort_text_size, " in coroutine %.256s (%p).\n", thrd->curr_cor->name, thrd->curr_cor );
578 __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
579 }
580 else {
581 __cfaabi_bits_write( STDERR_FILENO, ".\n", 2 );
582 }
583 }
584 else {
585 int len = snprintf( abort_text, abort_text_size, "Error occurred outside of any thread.\n" );
586 __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
587 }
588}
589
590int kernel_abort_lastframe( void ) __attribute__ ((__nothrow__)) {
591 return get_coroutine(kernelTLS.this_thread) == get_coroutine(mainThread) ? 4 : 2;
592}
593
594static __spinlock_t kernel_debug_lock;
595
596extern "C" {
597 void __cfaabi_bits_acquire() {
598 lock( kernel_debug_lock __cfaabi_dbg_ctx2 );
599 }
600
601 void __cfaabi_bits_release() {
602 unlock( kernel_debug_lock );
603 }
604}
605
606//=============================================================================================
607// Kernel Utilities
608//=============================================================================================
609//-----------------------------------------------------------------------------
610// Locks
611void ?{}( semaphore & this, int count = 1 ) {
612 (this.lock){};
613 this.count = count;
614 (this.waiting){};
615}
616void ^?{}(semaphore & this) {}
617
618bool P(semaphore & this) with( this ){
619 lock( lock __cfaabi_dbg_ctx2 );
620 count -= 1;
621 if ( count < 0 ) {
622 // queue current task
623 append( waiting, kernelTLS.this_thread );
624
625 // atomically release spin lock and block
626 unlock( lock );
627 park( __cfaabi_dbg_ctx );
628 return true;
629 }
630 else {
631 unlock( lock );
632 return false;
633 }
634}
635
636bool V(semaphore & this) with( this ) {
637 $thread * thrd = 0p;
638 lock( lock __cfaabi_dbg_ctx2 );
639 count += 1;
640 if ( count <= 0 ) {
641 // remove task at head of waiting list
642 thrd = pop_head( waiting );
643 }
644
645 unlock( lock );
646
647 // make new owner
648 unpark( thrd __cfaabi_dbg_ctx2 );
649
650 return thrd != 0p;
651}
652
653bool V(semaphore & this, unsigned diff) with( this ) {
654 $thread * thrd = 0p;
655 lock( lock __cfaabi_dbg_ctx2 );
656 int release = max(-count, (int)diff);
657 count += diff;
658 for(release) {
659 unpark( pop_head( waiting ) __cfaabi_dbg_ctx2 );
660 }
661
662 unlock( lock );
663
664 return thrd != 0p;
665}
666
667//-----------------------------------------------------------------------------
668// Debug
669__cfaabi_dbg_debug_do(
670 extern "C" {
671 void __cfaabi_dbg_record_lock(__spinlock_t & this, const char prev_name[]) {
672 this.prev_name = prev_name;
673 this.prev_thrd = kernelTLS.this_thread;
674 }
675
676 void __cfaabi_dbg_record_thrd($thread & this, bool park, const char prev_name[]) {
677 if(park) {
678 this.park_caller = prev_name;
679 this.park_stale = false;
680 }
681 else {
682 this.unpark_caller = prev_name;
683 this.unpark_stale = false;
684 }
685 }
686 }
687)
688
689//-----------------------------------------------------------------------------
690// Debug
691bool threading_enabled(void) __attribute__((const)) {
692 return true;
693}
694
695//-----------------------------------------------------------------------------
696// Statistics
697#if !defined(__CFA_NO_STATISTICS__)
698 void print_halts( processor & this ) {
699 this.print_halts = true;
700 }
701#endif
702// Local Variables: //
703// mode: c //
704// tab-width: 4 //
705// End: //
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