source: libcfa/src/concurrency/kernel.cfa @ 804c0ff

arm-ehjacob/cs343-translationnew-ast-unique-expr
Last change on this file since 804c0ff was 804c0ff, checked in by Thierry Delisle <tdelisle@…>, 9 months ago

Simplified abort handling in the case of concurrent abort.
I used to try to be fancy, now a lock-free algorithm just directly calls libc-abort on ANY subsequent/concurrent calls.

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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 : Mon Aug 31 07:08:20 2020
13// Update Count     : 71
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#elif defined( __arm__ )
77        #define __x87_store
78        #define __x87_load
79
80#elif defined( __aarch64__ )
81        #define __x87_store              \
82                uint32_t __fpcntl[2];    \
83                __asm__ volatile (    \
84                        "mrs x9, FPCR\n" \
85                        "mrs x10, FPSR\n"  \
86                        "stp x9, x10, %0\n"  \
87                        : "=m" (__fpcntl) : : "x9", "x10" \
88                )
89
90        #define __x87_load         \
91                __asm__ volatile (    \
92                        "ldp x9, x10, %0\n"  \
93                        "msr FPSR, x10\n"  \
94                        "msr FPCR, x9\n" \
95                : "=m" (__fpcntl) : : "x9", "x10" \
96                )
97
98#else
99        #error unsupported hardware architecture
100#endif
101
102extern $thread * mainThread;
103extern processor * mainProcessor;
104
105//-----------------------------------------------------------------------------
106// Kernel Scheduling logic
107static $thread * __next_thread(cluster * this);
108static $thread * __next_thread_slow(cluster * this);
109static void __run_thread(processor * this, $thread * dst);
110static void __wake_one(cluster * cltr);
111
112static void push  (__cluster_idles & idles, processor & proc);
113static void remove(__cluster_idles & idles, processor & proc);
114static [unsigned idle, unsigned total, * processor] query( & __cluster_idles idles );
115
116
117//=============================================================================================
118// Kernel Scheduling logic
119//=============================================================================================
120//Main of the processor contexts
121void main(processorCtx_t & runner) {
122        // Because of a bug, we couldn't initialized the seed on construction
123        // Do it here
124        __cfaabi_tls.rand_seed ^= rdtscl();
125        __cfaabi_tls.ready_rng.fwd_seed = 25214903917_l64u * (rdtscl() ^ (uintptr_t)&runner);
126        __tls_rand_advance_bck();
127
128        processor * this = runner.proc;
129        verify(this);
130
131        __cfadbg_print_safe(runtime_core, "Kernel : core %p starting\n", this);
132        #if !defined(__CFA_NO_STATISTICS__)
133                if( this->print_halts ) {
134                        __cfaabi_bits_print_safe( STDOUT_FILENO, "Processor : %d - %s (%p)\n", this->id, this->name, (void*)this);
135                }
136        #endif
137
138        {
139                // Setup preemption data
140                preemption_scope scope = { this };
141
142                #if !defined(__CFA_NO_STATISTICS__)
143                        unsigned long long last_tally = rdtscl();
144                #endif
145
146
147                __cfadbg_print_safe(runtime_core, "Kernel : core %p started\n", this);
148
149                $thread * readyThread = 0p;
150                MAIN_LOOP:
151                for() {
152                        // Try to get the next thread
153                        readyThread = __next_thread( this->cltr );
154
155                        if( !readyThread ) {
156                                readyThread = __next_thread_slow( this->cltr );
157                        }
158
159                        HALT:
160                        if( !readyThread ) {
161                                // Don't block if we are done
162                                if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
163
164                                #if !defined(__CFA_NO_STATISTICS__)
165                                        __tls_stats()->ready.sleep.halts++;
166                                #endif
167
168                                // Push self to idle stack
169                                push(this->cltr->idles, * this);
170
171                                // Confirm the ready-queue is empty
172                                readyThread = __next_thread_slow( this->cltr );
173                                if( readyThread ) {
174                                        // A thread was found, cancel the halt
175                                        remove(this->cltr->idles, * this);
176
177                                        #if !defined(__CFA_NO_STATISTICS__)
178                                                __tls_stats()->ready.sleep.cancels++;
179                                        #endif
180
181                                        // continue the mai loop
182                                        break HALT;
183                                }
184
185                                #if !defined(__CFA_NO_STATISTICS__)
186                                        if(this->print_halts) {
187                                                __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 0\n", this->id, rdtscl());
188                                        }
189                                #endif
190
191                                wait( this->idle );
192
193                                #if !defined(__CFA_NO_STATISTICS__)
194                                        if(this->print_halts) {
195                                                __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 1\n", this->id, rdtscl());
196                                        }
197                                #endif
198
199                                // We were woken up, remove self from idle
200                                remove(this->cltr->idles, * this);
201
202                                // DON'T just proceed, start looking again
203                                continue MAIN_LOOP;
204                        }
205
206                        /* paranoid */ verify( readyThread );
207
208                        // We found a thread run it
209                        __run_thread(this, readyThread);
210
211                        // Are we done?
212                        if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
213
214                        #if !defined(__CFA_NO_STATISTICS__)
215                                unsigned long long curr = rdtscl();
216                                if(curr > (last_tally + 500000000)) {
217                                        __tally_stats(this->cltr->stats, __cfaabi_tls.this_stats);
218                                        last_tally = curr;
219                                }
220                        #endif
221                }
222
223                __cfadbg_print_safe(runtime_core, "Kernel : core %p stopping\n", this);
224        }
225
226        V( this->terminated );
227
228        if(this == mainProcessor) {
229                // HACK : the coroutine context switch expects this_thread to be set
230                // and it make sense for it to be set in all other cases except here
231                // fake it
232                __cfaabi_tls.this_thread = mainThread;
233        }
234
235        __cfadbg_print_safe(runtime_core, "Kernel : core %p terminated\n", this);
236}
237
238static int * __volatile_errno() __attribute__((noinline));
239static int * __volatile_errno() { asm(""); return &errno; }
240
241// KERNEL ONLY
242// runThread runs a thread by context switching
243// from the processor coroutine to the target thread
244static void __run_thread(processor * this, $thread * thrd_dst) {
245        /* paranoid */ verify( ! __preemption_enabled() );
246        /* paranoid */ verifyf( thrd_dst->state == Ready || thrd_dst->preempted != __NO_PREEMPTION, "state : %d, preempted %d\n", thrd_dst->state, thrd_dst->preempted);
247        /* paranoid */ verifyf( thrd_dst->link.next == 0p, "Expected null got %p", thrd_dst->link.next );
248        __builtin_prefetch( thrd_dst->context.SP );
249
250        $coroutine * proc_cor = get_coroutine(this->runner);
251
252        // set state of processor coroutine to inactive
253        verify(proc_cor->state == Active);
254        proc_cor->state = Blocked;
255
256        // Actually run the thread
257        RUNNING:  while(true) {
258                thrd_dst->preempted = __NO_PREEMPTION;
259                thrd_dst->state = Active;
260
261                // Update global state
262                kernelTLS().this_thread = thrd_dst;
263
264                /* paranoid */ verify( ! __preemption_enabled() );
265                /* paranoid */ verify( kernelTLS().this_thread == thrd_dst );
266                /* paranoid */ verify( thrd_dst->curr_cluster == this->cltr );
267                /* paranoid */ verify( thrd_dst->context.SP );
268                /* paranoid */ verify( thrd_dst->state != Halted );
269                /* 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
270                /* 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
271                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_dst->canary );
272
273
274
275                // set context switch to the thread that the processor is executing
276                __cfactx_switch( &proc_cor->context, &thrd_dst->context );
277                // when __cfactx_switch returns we are back in the processor coroutine
278
279                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_dst->canary );
280                /* 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 );
281                /* 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 );
282                /* paranoid */ verify( thrd_dst->context.SP );
283                /* paranoid */ verify( thrd_dst->curr_cluster == this->cltr );
284                /* paranoid */ verify( kernelTLS().this_thread == thrd_dst );
285                /* paranoid */ verify( ! __preemption_enabled() );
286
287                // Reset global state
288                kernelTLS().this_thread = 0p;
289
290                // We just finished running a thread, there are a few things that could have happened.
291                // 1 - Regular case : the thread has blocked and now one has scheduled it yet.
292                // 2 - Racy case    : the thread has blocked but someone has already tried to schedule it.
293                // 4 - Preempted
294                // In case 1, we may have won a race so we can't write to the state again.
295                // In case 2, we lost the race so we now own the thread.
296
297                if(unlikely(thrd_dst->preempted != __NO_PREEMPTION)) {
298                        // The thread was preempted, reschedule it and reset the flag
299                        __schedule_thread( thrd_dst );
300                        break RUNNING;
301                }
302
303                if(unlikely(thrd_dst->state == Halting)) {
304                        // The thread has halted, it should never be scheduled/run again
305                        // finish the thread
306                        __thread_finish( thrd_dst );
307                        break RUNNING;
308                }
309
310                /* paranoid */ verify( thrd_dst->state == Active );
311                thrd_dst->state = Blocked;
312
313                // set state of processor coroutine to active and the thread to inactive
314                int old_ticket = __atomic_fetch_sub(&thrd_dst->ticket, 1, __ATOMIC_SEQ_CST);
315                switch(old_ticket) {
316                        case TICKET_RUNNING:
317                                // This is case 1, the regular case, nothing more is needed
318                                break RUNNING;
319                        case TICKET_UNBLOCK:
320                                // This is case 2, the racy case, someone tried to run this thread before it finished blocking
321                                // In this case, just run it again.
322                                continue RUNNING;
323                        default:
324                                // This makes no sense, something is wrong abort
325                                abort();
326                }
327        }
328
329        // Just before returning to the processor, set the processor coroutine to active
330        proc_cor->state = Active;
331
332        /* paranoid */ verify( ! __preemption_enabled() );
333}
334
335// KERNEL_ONLY
336void returnToKernel() {
337        /* paranoid */ verify( ! __preemption_enabled() );
338        $coroutine * proc_cor = get_coroutine(kernelTLS().this_processor->runner);
339        $thread * thrd_src = kernelTLS().this_thread;
340
341        #if !defined(__CFA_NO_STATISTICS__)
342                struct processor * last_proc = kernelTLS().this_processor;
343        #endif
344
345        // Run the thread on this processor
346        {
347                int local_errno = *__volatile_errno();
348                #if defined( __i386 ) || defined( __x86_64 )
349                        __x87_store;
350                #endif
351                /* paranoid */ verify( proc_cor->context.SP );
352                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_src->canary );
353                __cfactx_switch( &thrd_src->context, &proc_cor->context );
354                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_src->canary );
355                #if defined( __i386 ) || defined( __x86_64 )
356                        __x87_load;
357                #endif
358                *__volatile_errno() = local_errno;
359        }
360
361        #if !defined(__CFA_NO_STATISTICS__)
362                if(last_proc != kernelTLS().this_processor) {
363                        __tls_stats()->ready.threads.migration++;
364                }
365        #endif
366
367        /* paranoid */ verify( ! __preemption_enabled() );
368        /* 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 );
369        /* 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 );
370}
371
372//-----------------------------------------------------------------------------
373// Scheduler routines
374// KERNEL ONLY
375void __schedule_thread( $thread * thrd ) {
376        /* paranoid */ verify( ! __preemption_enabled() );
377        /* paranoid */ verify( kernelTLS().this_proc_id );
378        /* paranoid */ verify( thrd );
379        /* paranoid */ verify( thrd->state != Halted );
380        /* paranoid */ verify( thrd->curr_cluster );
381        /* paranoid */ #if defined( __CFA_WITH_VERIFY__ )
382        /* paranoid */  if( thrd->state == Blocked || thrd->state == Start ) assertf( thrd->preempted == __NO_PREEMPTION,
383                                        "Error inactive thread marked as preempted, state %d, preemption %d\n", thrd->state, thrd->preempted );
384        /* paranoid */  if( thrd->preempted != __NO_PREEMPTION ) assertf(thrd->state == Active,
385                                        "Error preempted thread marked as not currently running, state %d, preemption %d\n", thrd->state, thrd->preempted );
386        /* paranoid */ #endif
387        /* paranoid */ verifyf( thrd->link.next == 0p, "Expected null got %p", thrd->link.next );
388        /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd->canary );
389
390
391        if (thrd->preempted == __NO_PREEMPTION) thrd->state = Ready;
392
393        ready_schedule_lock();
394                // Dereference the thread now because once we push it, there is not guaranteed it's still valid.
395                struct cluster * cl = thrd->curr_cluster;
396
397                // push the thread to the cluster ready-queue
398                push( cl, thrd );
399
400                // variable thrd is no longer safe to use
401
402                // wake the cluster using the save variable.
403                __wake_one( cl );
404        ready_schedule_unlock();
405
406        /* paranoid */ verify( ! __preemption_enabled() );
407}
408
409// KERNEL ONLY
410static inline $thread * __next_thread(cluster * this) with( *this ) {
411        /* paranoid */ verify( ! __preemption_enabled() );
412        /* paranoid */ verify( kernelTLS().this_proc_id );
413
414        ready_schedule_lock();
415                $thread * thrd = pop( this );
416        ready_schedule_unlock();
417
418        /* paranoid */ verify( kernelTLS().this_proc_id );
419        /* paranoid */ verify( ! __preemption_enabled() );
420        return thrd;
421}
422
423// KERNEL ONLY
424static inline $thread * __next_thread_slow(cluster * this) with( *this ) {
425        /* paranoid */ verify( ! __preemption_enabled() );
426        /* paranoid */ verify( kernelTLS().this_proc_id );
427
428        ready_schedule_lock();
429                $thread * thrd = pop_slow( this );
430        ready_schedule_unlock();
431
432        /* paranoid */ verify( kernelTLS().this_proc_id );
433        /* paranoid */ verify( ! __preemption_enabled() );
434        return thrd;
435}
436
437void unpark( $thread * thrd ) {
438        if( !thrd ) return;
439
440        int old_ticket = __atomic_fetch_add(&thrd->ticket, 1, __ATOMIC_SEQ_CST);
441        switch(old_ticket) {
442                case TICKET_RUNNING:
443                        // Wake won the race, the thread will reschedule/rerun itself
444                        break;
445                case TICKET_BLOCKED:
446                        /* paranoid */ verify( ! thrd->preempted != __NO_PREEMPTION );
447                        /* paranoid */ verify( thrd->state == Blocked );
448
449                        {
450                                /* paranoid */ verify( publicTLS_get(this_proc_id) );
451                                bool full = publicTLS_get(this_proc_id)->full_proc;
452                                if(full) disable_interrupts();
453
454                                /* paranoid */ verify( ! __preemption_enabled() );
455
456                                // Wake lost the race,
457                                __schedule_thread( thrd );
458
459                                /* paranoid */ verify( ! __preemption_enabled() );
460
461                                if(full) enable_interrupts( __cfaabi_dbg_ctx );
462                                /* paranoid */ verify( publicTLS_get(this_proc_id) );
463                        }
464
465                        break;
466                default:
467                        // This makes no sense, something is wrong abort
468                        abort("Thread %p (%s) has mismatch park/unpark\n", thrd, thrd->self_cor.name);
469        }
470}
471
472void park( void ) {
473        /* paranoid */ verify( __preemption_enabled() );
474        disable_interrupts();
475        /* paranoid */ verify( ! __preemption_enabled() );
476        /* paranoid */ verify( kernelTLS().this_thread->preempted == __NO_PREEMPTION );
477
478        returnToKernel();
479
480        /* paranoid */ verify( ! __preemption_enabled() );
481        enable_interrupts( __cfaabi_dbg_ctx );
482        /* paranoid */ verify( __preemption_enabled() );
483
484}
485
486extern "C" {
487        // Leave the thread monitor
488        // last routine called by a thread.
489        // Should never return
490        void __cfactx_thrd_leave() {
491                $thread * thrd = active_thread();
492                $monitor * this = &thrd->self_mon;
493
494                // Lock the monitor now
495                lock( this->lock __cfaabi_dbg_ctx2 );
496
497                disable_interrupts();
498
499                /* paranoid */ verify( ! __preemption_enabled() );
500                /* paranoid */ verify( thrd->state == Active );
501                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd->canary );
502                /* paranoid */ verify( kernelTLS().this_thread == thrd );
503                /* paranoid */ verify( thrd->context.SP );
504                /* paranoid */ verifyf( ((uintptr_t)thrd->context.SP) > ((uintptr_t)__get_stack(thrd->curr_cor)->limit), "ERROR : $thread %p has been corrupted.\n StackPointer too large.\n", thrd );
505                /* paranoid */ verifyf( ((uintptr_t)thrd->context.SP) < ((uintptr_t)__get_stack(thrd->curr_cor)->base ), "ERROR : $thread %p has been corrupted.\n StackPointer too small.\n", thrd );
506
507                thrd->state = Halting;
508                if( TICKET_RUNNING != thrd->ticket ) { abort( "Thread terminated with pending unpark" ); }
509                if( thrd != this->owner ) { abort( "Thread internal monitor has incorrect owner" ); }
510                if( this->recursion != 1) { abort( "Thread internal monitor has unbalanced recursion" ); }
511
512                // Leave the thread
513                returnToKernel();
514
515                // Control flow should never reach here!
516                abort();
517        }
518}
519
520// KERNEL ONLY
521bool force_yield( __Preemption_Reason reason ) {
522        /* paranoid */ verify( __preemption_enabled() );
523        disable_interrupts();
524        /* paranoid */ verify( ! __preemption_enabled() );
525
526        $thread * thrd = kernelTLS().this_thread;
527        /* paranoid */ verify(thrd->state == Active);
528
529        // SKULLDUGGERY: It is possible that we are preempting this thread just before
530        // it was going to park itself. If that is the case and it is already using the
531        // intrusive fields then we can't use them to preempt the thread
532        // If that is the case, abandon the preemption.
533        bool preempted = false;
534        if(thrd->link.next == 0p) {
535                preempted = true;
536                thrd->preempted = reason;
537                returnToKernel();
538        }
539
540        /* paranoid */ verify( ! __preemption_enabled() );
541        enable_interrupts_noPoll();
542        /* paranoid */ verify( __preemption_enabled() );
543
544        return preempted;
545}
546
547//=============================================================================================
548// Kernel Idle Sleep
549//=============================================================================================
550// Wake a thread from the front if there are any
551static void __wake_one(cluster * this) {
552        /* paranoid */ verify( ! __preemption_enabled() );
553        /* paranoid */ verify( ready_schedule_islocked() );
554
555        // Check if there is a sleeping processor
556        processor * p;
557        unsigned idle;
558        unsigned total;
559        [idle, total, p] = query(this->idles);
560
561        // If no one is sleeping, we are done
562        if( idle == 0 ) return;
563
564        // We found a processor, wake it up
565        post( p->idle );
566
567        #if !defined(__CFA_NO_STATISTICS__)
568                __tls_stats()->ready.sleep.wakes++;
569        #endif
570
571        /* paranoid */ verify( ready_schedule_islocked() );
572        /* paranoid */ verify( ! __preemption_enabled() );
573
574        return;
575}
576
577// Unconditionnaly wake a thread
578void __wake_proc(processor * this) {
579        __cfadbg_print_safe(runtime_core, "Kernel : waking Processor %p\n", this);
580
581        disable_interrupts();
582                /* paranoid */ verify( ! __preemption_enabled() );
583                post( this->idle );
584        enable_interrupts( __cfaabi_dbg_ctx );
585}
586
587static void push  (__cluster_idles & this, processor & proc) {
588        /* paranoid */ verify( ! __preemption_enabled() );
589        lock( this );
590                this.idle++;
591                /* paranoid */ verify( this.idle <= this.total );
592
593                insert_first(this.list, proc);
594        unlock( this );
595        /* paranoid */ verify( ! __preemption_enabled() );
596}
597
598static void remove(__cluster_idles & this, processor & proc) {
599        /* paranoid */ verify( ! __preemption_enabled() );
600        lock( this );
601                this.idle--;
602                /* paranoid */ verify( this.idle >= 0 );
603
604                remove(proc);
605        unlock( this );
606        /* paranoid */ verify( ! __preemption_enabled() );
607}
608
609static [unsigned idle, unsigned total, * processor] query( & __cluster_idles this ) {
610        for() {
611                uint64_t l = __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST);
612                if( 1 == (l % 2) ) { Pause(); continue; }
613                unsigned idle    = this.idle;
614                unsigned total   = this.total;
615                processor * proc = &this.list`first;
616                // Compiler fence is unnecessary, but gcc-8 and older incorrectly reorder code without it
617                asm volatile("": : :"memory");
618                if(l != __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST)) { Pause(); continue; }
619                return [idle, total, proc];
620        }
621}
622
623//=============================================================================================
624// Unexpected Terminating logic
625//=============================================================================================
626
627extern "C" {
628        extern void __cfaabi_real_abort(void);
629}
630static volatile bool kernel_abort_called = false;
631
632void * kernel_abort(void) __attribute__ ((__nothrow__)) {
633        // abort cannot be recursively entered by the same or different processors because all signal handlers return when
634        // the globalAbort flag is true.
635        bool first = __atomic_test_and_set( &kernel_abort_called, __ATOMIC_SEQ_CST);
636
637        // first task to abort ?
638        if ( !first ) {
639                // We aren't the first to abort.
640                // I give up, just let C handle it
641                __cfaabi_real_abort();
642        }
643
644        // disable interrupts, it no longer makes sense to try to interrupt this processor
645        disable_interrupts();
646
647        return __cfaabi_tls.this_thread;
648}
649
650void kernel_abort_msg( void * kernel_data, char * abort_text, int abort_text_size ) {
651        $thread * thrd = ( $thread * ) kernel_data;
652
653        if(thrd) {
654                int len = snprintf( abort_text, abort_text_size, "Error occurred while executing thread %.256s (%p)", thrd->self_cor.name, thrd );
655                __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
656
657                if ( &thrd->self_cor != thrd->curr_cor ) {
658                        len = snprintf( abort_text, abort_text_size, " in coroutine %.256s (%p).\n", thrd->curr_cor->name, thrd->curr_cor );
659                        __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
660                }
661                else {
662                        __cfaabi_bits_write( STDERR_FILENO, ".\n", 2 );
663                }
664        }
665        else {
666                int len = snprintf( abort_text, abort_text_size, "Error occurred outside of any thread.\n" );
667                __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
668        }
669}
670
671int kernel_abort_lastframe( void ) __attribute__ ((__nothrow__)) {
672        return get_coroutine(kernelTLS().this_thread) == get_coroutine(mainThread) ? 4 : 2;
673}
674
675static __spinlock_t kernel_debug_lock;
676
677extern "C" {
678        void __cfaabi_bits_acquire() {
679                lock( kernel_debug_lock __cfaabi_dbg_ctx2 );
680        }
681
682        void __cfaabi_bits_release() {
683                unlock( kernel_debug_lock );
684        }
685}
686
687//=============================================================================================
688// Kernel Utilities
689//=============================================================================================
690//-----------------------------------------------------------------------------
691// Locks
692void  ?{}( semaphore & this, int count = 1 ) {
693        (this.lock){};
694        this.count = count;
695        (this.waiting){};
696}
697void ^?{}(semaphore & this) {}
698
699bool P(semaphore & this) with( this ){
700        lock( lock __cfaabi_dbg_ctx2 );
701        count -= 1;
702        if ( count < 0 ) {
703                // queue current task
704                append( waiting, active_thread() );
705
706                // atomically release spin lock and block
707                unlock( lock );
708                park();
709                return true;
710        }
711        else {
712            unlock( lock );
713            return false;
714        }
715}
716
717bool V(semaphore & this) with( this ) {
718        $thread * thrd = 0p;
719        lock( lock __cfaabi_dbg_ctx2 );
720        count += 1;
721        if ( count <= 0 ) {
722                // remove task at head of waiting list
723                thrd = pop_head( waiting );
724        }
725
726        unlock( lock );
727
728        // make new owner
729        unpark( thrd );
730
731        return thrd != 0p;
732}
733
734bool V(semaphore & this, unsigned diff) with( this ) {
735        $thread * thrd = 0p;
736        lock( lock __cfaabi_dbg_ctx2 );
737        int release = max(-count, (int)diff);
738        count += diff;
739        for(release) {
740                unpark( pop_head( waiting ) );
741        }
742
743        unlock( lock );
744
745        return thrd != 0p;
746}
747
748//-----------------------------------------------------------------------------
749// Debug
750__cfaabi_dbg_debug_do(
751        extern "C" {
752                void __cfaabi_dbg_record_lock(__spinlock_t & this, const char prev_name[]) {
753                        this.prev_name = prev_name;
754                        this.prev_thrd = kernelTLS().this_thread;
755                }
756        }
757)
758
759//-----------------------------------------------------------------------------
760// Debug
761bool threading_enabled(void) __attribute__((const)) {
762        return true;
763}
764
765//-----------------------------------------------------------------------------
766// Statistics
767#if !defined(__CFA_NO_STATISTICS__)
768        void print_halts( processor & this ) {
769                this.print_halts = true;
770        }
771
772        void print_stats_now( cluster & this, int flags ) {
773                __print_stats( this.stats, this.print_stats, "Cluster", this.name, (void*)&this );
774        }
775
776        extern int __print_alarm_stats;
777        void print_alarm_stats() {
778                __print_alarm_stats = -1;
779        }
780#endif
781// Local Variables: //
782// mode: c //
783// tab-width: 4 //
784// End: //
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