source: libcfa/src/concurrency/kernel.cfa @ 153d0f52

ADTarm-ehast-experimentalenumforall-pointer-decayjacob/cs343-translationnew-astnew-ast-unique-exprpthread-emulationqualifiedEnum
Last change on this file since 153d0f52 was 1eb239e4, checked in by Thierry Delisle <tdelisle@…>, 4 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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