source: libcfa/src/concurrency/kernel.cfa @ ab5baab

ADTarm-ehast-experimentalenumforall-pointer-decayjacob/cs343-translationnew-ast-unique-exprpthread-emulationqualifiedEnum
Last change on this file since ab5baab was ab5baab, checked in by Thierry Delisle <tdelisle@…>, 3 years ago

Attempt to fix the stack checker for when coroutines are interrupted at the wrong moment

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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>
24extern "C" {
25        #include <sys/eventfd.h>
26}
27
28//CFA Includes
29#include "kernel_private.hfa"
30#include "preemption.hfa"
31
32//Private includes
33#define __CFA_INVOKE_PRIVATE__
34#include "invoke.h"
35
36#if !defined(__CFA_NO_STATISTICS__)
37        #define __STATS( ...) __VA_ARGS__
38#else
39        #define __STATS( ...)
40#endif
41
42//-----------------------------------------------------------------------------
43// Some assembly required
44#if defined( __i386 )
45        // mxcr : SSE Status and Control bits (control bits are preserved across function calls)
46        // fcw  : X87 FPU control word (preserved across function calls)
47        #define __x87_store         \
48                uint32_t __mxcr;      \
49                uint16_t __fcw;       \
50                __asm__ volatile (    \
51                        "stmxcsr %0\n"  \
52                        "fnstcw  %1\n"  \
53                        : "=m" (__mxcr),\
54                                "=m" (__fcw)  \
55                )
56
57        #define __x87_load         \
58                __asm__ volatile (   \
59                        "fldcw  %1\n"  \
60                        "ldmxcsr %0\n" \
61                        ::"m" (__mxcr),\
62                                "m" (__fcw)  \
63                )
64
65#elif defined( __x86_64 )
66        #define __x87_store         \
67                uint32_t __mxcr;      \
68                uint16_t __fcw;       \
69                __asm__ volatile (    \
70                        "stmxcsr %0\n"  \
71                        "fnstcw  %1\n"  \
72                        : "=m" (__mxcr),\
73                                "=m" (__fcw)  \
74                )
75
76        #define __x87_load          \
77                __asm__ volatile (    \
78                        "fldcw  %1\n"   \
79                        "ldmxcsr %0\n"  \
80                        :: "m" (__mxcr),\
81                                "m" (__fcw)  \
82                )
83
84#elif defined( __arm__ )
85        #define __x87_store
86        #define __x87_load
87
88#elif defined( __aarch64__ )
89        #define __x87_store              \
90                uint32_t __fpcntl[2];    \
91                __asm__ volatile (    \
92                        "mrs x9, FPCR\n" \
93                        "mrs x10, FPSR\n"  \
94                        "stp x9, x10, %0\n"  \
95                        : "=m" (__fpcntl) : : "x9", "x10" \
96                )
97
98        #define __x87_load         \
99                __asm__ volatile (    \
100                        "ldp x9, x10, %0\n"  \
101                        "msr FPSR, x10\n"  \
102                        "msr FPCR, x9\n" \
103                : "=m" (__fpcntl) : : "x9", "x10" \
104                )
105
106#else
107        #error unsupported hardware architecture
108#endif
109
110extern $thread * mainThread;
111extern processor * mainProcessor;
112
113//-----------------------------------------------------------------------------
114// Kernel Scheduling logic
115static $thread * __next_thread(cluster * this);
116static $thread * __next_thread_slow(cluster * this);
117static inline bool __must_unpark( $thread * thrd ) __attribute((nonnull(1)));
118static void __run_thread(processor * this, $thread * dst);
119static void __wake_one(cluster * cltr);
120
121static void mark_idle (__cluster_proc_list & idles, processor & proc);
122static void mark_awake(__cluster_proc_list & idles, processor & proc);
123static [unsigned idle, unsigned total, * processor] query_idles( & __cluster_proc_list idles );
124
125extern void __cfa_io_start( processor * );
126extern bool __cfa_io_drain( processor * );
127extern void __cfa_io_flush( processor * );
128extern void __cfa_io_stop ( processor * );
129static inline bool __maybe_io_drain( processor * );
130
131extern void __disable_interrupts_hard();
132extern void __enable_interrupts_hard();
133
134static inline void __disable_interrupts_checked() {
135        /* paranoid */ verify( __preemption_enabled() );
136        disable_interrupts();
137        /* paranoid */ verify( ! __preemption_enabled() );
138}
139
140static inline void __enable_interrupts_checked( bool poll = true ) {
141        /* paranoid */ verify( ! __preemption_enabled() );
142        enable_interrupts( poll );
143        /* paranoid */ verify( __preemption_enabled() );
144}
145
146//=============================================================================================
147// Kernel Scheduling logic
148//=============================================================================================
149//Main of the processor contexts
150void main(processorCtx_t & runner) {
151        // Because of a bug, we couldn't initialized the seed on construction
152        // Do it here
153        __cfaabi_tls.rand_seed ^= rdtscl();
154        __cfaabi_tls.ready_rng.fwd_seed = 25214903917_l64u * (rdtscl() ^ (uintptr_t)&runner);
155        __tls_rand_advance_bck();
156
157        processor * this = runner.proc;
158        verify(this);
159
160        __cfa_io_start( this );
161
162        __cfadbg_print_safe(runtime_core, "Kernel : core %p starting\n", this);
163        #if !defined(__CFA_NO_STATISTICS__)
164                if( this->print_halts ) {
165                        __cfaabi_bits_print_safe( STDOUT_FILENO, "Processor : %d - %s (%p)\n", this->unique_id, this->name, (void*)this);
166                }
167        #endif
168
169        {
170                // Setup preemption data
171                preemption_scope scope = { this };
172
173                // if we need to run some special setup, now is the time to do it.
174                if(this->init.thrd) {
175                        this->init.thrd->curr_cluster = this->cltr;
176                        __run_thread(this, this->init.thrd);
177                }
178
179                __cfadbg_print_safe(runtime_core, "Kernel : core %p started\n", this);
180
181                $thread * readyThread = 0p;
182                MAIN_LOOP:
183                for() {
184                        #define OLD_MAIN 1
185                        #if OLD_MAIN
186                        // Check if there is pending io
187                        __maybe_io_drain( this );
188
189                        // Try to get the next thread
190                        readyThread = __next_thread( this->cltr );
191
192                        if( !readyThread ) {
193                                __cfa_io_flush( this );
194                                readyThread = __next_thread_slow( this->cltr );
195                        }
196
197                        HALT:
198                        if( !readyThread ) {
199                                // Don't block if we are done
200                                if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
201
202                                #if !defined(__CFA_NO_STATISTICS__)
203                                        __tls_stats()->ready.sleep.halts++;
204                                #endif
205
206                                // Push self to idle stack
207                                mark_idle(this->cltr->procs, * this);
208
209                                // Confirm the ready-queue is empty
210                                readyThread = __next_thread_slow( this->cltr );
211                                if( readyThread ) {
212                                        // A thread was found, cancel the halt
213                                        mark_awake(this->cltr->procs, * this);
214
215                                        #if !defined(__CFA_NO_STATISTICS__)
216                                                __tls_stats()->ready.sleep.cancels++;
217                                        #endif
218
219                                        // continue the mai loop
220                                        break HALT;
221                                }
222
223                                #if !defined(__CFA_NO_STATISTICS__)
224                                        if(this->print_halts) {
225                                                __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 0\n", this->unique_id, rdtscl());
226                                        }
227                                #endif
228
229                                __cfadbg_print_safe(runtime_core, "Kernel : core %p waiting on eventfd %d\n", this, this->idle);
230
231                                __disable_interrupts_hard();
232                                eventfd_t val;
233                                eventfd_read( this->idle, &val );
234                                __enable_interrupts_hard();
235
236                                #if !defined(__CFA_NO_STATISTICS__)
237                                        if(this->print_halts) {
238                                                __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 1\n", this->unique_id, rdtscl());
239                                        }
240                                #endif
241
242                                // We were woken up, remove self from idle
243                                mark_awake(this->cltr->procs, * this);
244
245                                // DON'T just proceed, start looking again
246                                continue MAIN_LOOP;
247                        }
248
249                        /* paranoid */ verify( readyThread );
250
251                        // Reset io dirty bit
252                        this->io.dirty = false;
253
254                        // We found a thread run it
255                        __run_thread(this, readyThread);
256
257                        // Are we done?
258                        if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
259
260                        if(this->io.pending && !this->io.dirty) {
261                                __cfa_io_flush( this );
262                        }
263
264                        #else
265                                #warning new kernel loop
266                        SEARCH: {
267                                /* paranoid */ verify( ! __preemption_enabled() );
268
269                                // First, lock the scheduler since we are searching for a thread
270                                ready_schedule_lock();
271
272                                // Try to get the next thread
273                                readyThread = pop_fast( this->cltr );
274                                if(readyThread) { ready_schedule_unlock(); break SEARCH; }
275
276                                // If we can't find a thread, might as well flush any outstanding I/O
277                                if(this->io.pending) { __cfa_io_flush( this ); }
278
279                                // Spin a little on I/O, just in case
280                                        for(5) {
281                                        __maybe_io_drain( this );
282                                        readyThread = pop_fast( this->cltr );
283                                        if(readyThread) { ready_schedule_unlock(); break SEARCH; }
284                                }
285
286                                // no luck, try stealing a few times
287                                        for(5) {
288                                        if( __maybe_io_drain( this ) ) {
289                                                readyThread = pop_fast( this->cltr );
290                                        } else {
291                                                readyThread = pop_slow( this->cltr );
292                                        }
293                                        if(readyThread) { ready_schedule_unlock(); break SEARCH; }
294                                }
295
296                                // still no luck, search for a thread
297                                readyThread = pop_search( this->cltr );
298                                if(readyThread) { ready_schedule_unlock(); break SEARCH; }
299
300                                // Don't block if we are done
301                                if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
302
303                                __STATS( __tls_stats()->ready.sleep.halts++; )
304
305                                // Push self to idle stack
306                                ready_schedule_unlock();
307                                mark_idle(this->cltr->procs, * this);
308                                ready_schedule_lock();
309
310                                // Confirm the ready-queue is empty
311                                __maybe_io_drain( this );
312                                readyThread = pop_search( this->cltr );
313                                ready_schedule_unlock();
314
315                                if( readyThread ) {
316                                        // A thread was found, cancel the halt
317                                        mark_awake(this->cltr->procs, * this);
318
319                                        __STATS( __tls_stats()->ready.sleep.cancels++; )
320
321                                        // continue the main loop
322                                        break SEARCH;
323                                }
324
325                                        __STATS( if(this->print_halts) __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 0\n", this->unique_id, rdtscl()); )
326                                __cfadbg_print_safe(runtime_core, "Kernel : core %p waiting on eventfd %d\n", this, this->idle);
327
328                                // __disable_interrupts_hard();
329                                eventfd_t val;
330                                eventfd_read( this->idle, &val );
331                                // __enable_interrupts_hard();
332
333                                        __STATS( if(this->print_halts) __cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 1\n", this->unique_id, rdtscl()); )
334
335                                // We were woken up, remove self from idle
336                                mark_awake(this->cltr->procs, * this);
337
338                                // DON'T just proceed, start looking again
339                                continue MAIN_LOOP;
340                        }
341
342                RUN_THREAD:
343                        /* paranoid */ verify( ! __preemption_enabled() );
344                        /* paranoid */ verify( readyThread );
345
346                        // Reset io dirty bit
347                        this->io.dirty = false;
348
349                        // We found a thread run it
350                        __run_thread(this, readyThread);
351
352                        // Are we done?
353                        if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
354
355                        if(this->io.pending && !this->io.dirty) {
356                                __cfa_io_flush( this );
357                        }
358
359                        ready_schedule_lock();
360                        __maybe_io_drain( this );
361                        ready_schedule_unlock();
362                        #endif
363                }
364
365                __cfadbg_print_safe(runtime_core, "Kernel : core %p stopping\n", this);
366        }
367
368        __cfa_io_stop( this );
369
370        post( this->terminated );
371
372        if(this == mainProcessor) {
373                // HACK : the coroutine context switch expects this_thread to be set
374                // and it make sense for it to be set in all other cases except here
375                // fake it
376                __cfaabi_tls.this_thread = mainThread;
377        }
378
379        __cfadbg_print_safe(runtime_core, "Kernel : core %p terminated\n", this);
380}
381
382static int * __volatile_errno() __attribute__((noinline));
383static int * __volatile_errno() { asm(""); return &errno; }
384
385// KERNEL ONLY
386// runThread runs a thread by context switching
387// from the processor coroutine to the target thread
388static void __run_thread(processor * this, $thread * thrd_dst) {
389        /* paranoid */ verify( ! __preemption_enabled() );
390        /* paranoid */ verifyf( thrd_dst->state == Ready || thrd_dst->preempted != __NO_PREEMPTION, "state : %d, preempted %d\n", thrd_dst->state, thrd_dst->preempted);
391        /* paranoid */ verifyf( thrd_dst->link.next == 0p, "Expected null got %p", thrd_dst->link.next );
392        __builtin_prefetch( thrd_dst->context.SP );
393
394        __cfadbg_print_safe(runtime_core, "Kernel : core %p running thread %p (%s)\n", this, thrd_dst, thrd_dst->self_cor.name);
395
396        $coroutine * proc_cor = get_coroutine(this->runner);
397
398        // set state of processor coroutine to inactive
399        verify(proc_cor->state == Active);
400        proc_cor->state = Blocked;
401
402        // Actually run the thread
403        RUNNING:  while(true) {
404                thrd_dst->preempted = __NO_PREEMPTION;
405                thrd_dst->state = Active;
406
407                // Update global state
408                kernelTLS().this_thread = thrd_dst;
409
410                /* paranoid */ verify( ! __preemption_enabled() );
411                /* paranoid */ verify( kernelTLS().this_thread == thrd_dst );
412                /* paranoid */ verify( thrd_dst->curr_cluster == this->cltr );
413                /* paranoid */ verify( thrd_dst->context.SP );
414                /* paranoid */ verify( thrd_dst->state != Halted );
415                /* 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
416                /* 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
417                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_dst->canary );
418
419
420
421                // set context switch to the thread that the processor is executing
422                __cfactx_switch( &proc_cor->context, &thrd_dst->context );
423                // when __cfactx_switch returns we are back in the processor coroutine
424
425                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_dst->canary );
426                /* paranoid */ verifyf( ((uintptr_t)thrd_dst->context.SP) > ((uintptr_t)__get_stack(thrd_dst->curr_cor)->limit) || thrd_dst->corctx_flag, "ERROR : Destination $thread %p has been corrupted.\n StackPointer too large.\n", thrd_dst );
427                /* paranoid */ verifyf( ((uintptr_t)thrd_dst->context.SP) < ((uintptr_t)__get_stack(thrd_dst->curr_cor)->base ) || thrd_dst->corctx_flag, "ERROR : Destination $thread %p has been corrupted.\n StackPointer too small.\n", thrd_dst );
428                /* paranoid */ verify( thrd_dst->context.SP );
429                /* paranoid */ verify( thrd_dst->curr_cluster == this->cltr );
430                /* paranoid */ verify( kernelTLS().this_thread == thrd_dst );
431                /* paranoid */ verify( ! __preemption_enabled() );
432
433                // Reset global state
434                kernelTLS().this_thread = 0p;
435
436                // We just finished running a thread, there are a few things that could have happened.
437                // 1 - Regular case : the thread has blocked and now one has scheduled it yet.
438                // 2 - Racy case    : the thread has blocked but someone has already tried to schedule it.
439                // 4 - Preempted
440                // In case 1, we may have won a race so we can't write to the state again.
441                // In case 2, we lost the race so we now own the thread.
442
443                if(unlikely(thrd_dst->preempted != __NO_PREEMPTION)) {
444                        // The thread was preempted, reschedule it and reset the flag
445                        schedule_thread$( thrd_dst );
446                        break RUNNING;
447                }
448
449                if(unlikely(thrd_dst->state == Halting)) {
450                        // The thread has halted, it should never be scheduled/run again
451                        // finish the thread
452                        __thread_finish( thrd_dst );
453                        break RUNNING;
454                }
455
456                /* paranoid */ verify( thrd_dst->state == Active );
457                thrd_dst->state = Blocked;
458
459                // set state of processor coroutine to active and the thread to inactive
460                int old_ticket = __atomic_fetch_sub(&thrd_dst->ticket, 1, __ATOMIC_SEQ_CST);
461                switch(old_ticket) {
462                        case TICKET_RUNNING:
463                                // This is case 1, the regular case, nothing more is needed
464                                break RUNNING;
465                        case TICKET_UNBLOCK:
466                                #if !defined(__CFA_NO_STATISTICS__)
467                                        __tls_stats()->ready.threads.threads++;
468                                        __push_stat( __tls_stats(), __tls_stats()->ready.threads.threads, false, "Processor", this );
469                                #endif
470                                // This is case 2, the racy case, someone tried to run this thread before it finished blocking
471                                // In this case, just run it again.
472                                continue RUNNING;
473                        default:
474                                // This makes no sense, something is wrong abort
475                                abort();
476                }
477        }
478
479        // Just before returning to the processor, set the processor coroutine to active
480        proc_cor->state = Active;
481
482        __cfadbg_print_safe(runtime_core, "Kernel : core %p finished running thread %p\n", this, thrd_dst);
483
484        #if !defined(__CFA_NO_STATISTICS__)
485                __tls_stats()->ready.threads.threads--;
486                __push_stat( __tls_stats(), __tls_stats()->ready.threads.threads, false, "Processor", this );
487        #endif
488
489        /* paranoid */ verify( ! __preemption_enabled() );
490}
491
492// KERNEL_ONLY
493void returnToKernel() {
494        /* paranoid */ verify( ! __preemption_enabled() );
495        $coroutine * proc_cor = get_coroutine(kernelTLS().this_processor->runner);
496        $thread * thrd_src = kernelTLS().this_thread;
497
498        __STATS( thrd_src->last_proc = kernelTLS().this_processor; )
499
500        // Run the thread on this processor
501        {
502                int local_errno = *__volatile_errno();
503                #if defined( __i386 ) || defined( __x86_64 )
504                        __x87_store;
505                #endif
506                /* paranoid */ verify( proc_cor->context.SP );
507                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_src->canary );
508                __cfactx_switch( &thrd_src->context, &proc_cor->context );
509                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd_src->canary );
510                #if defined( __i386 ) || defined( __x86_64 )
511                        __x87_load;
512                #endif
513                *__volatile_errno() = local_errno;
514        }
515
516        #if !defined(__CFA_NO_STATISTICS__)
517                /* paranoid */ verify( thrd_src->last_proc != 0p );
518                if(thrd_src->last_proc != kernelTLS().this_processor) {
519                        __tls_stats()->ready.threads.migration++;
520                }
521        #endif
522
523        /* paranoid */ verify( ! __preemption_enabled() );
524        /* 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 );
525        /* 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 );
526}
527
528//-----------------------------------------------------------------------------
529// Scheduler routines
530// KERNEL ONLY
531static void __schedule_thread( $thread * thrd ) {
532        /* paranoid */ verify( ! __preemption_enabled() );
533        /* paranoid */ verify( ready_schedule_islocked());
534        /* paranoid */ verify( thrd );
535        /* paranoid */ verify( thrd->state != Halted );
536        /* paranoid */ verify( thrd->curr_cluster );
537        /* paranoid */ #if defined( __CFA_WITH_VERIFY__ )
538        /* paranoid */  if( thrd->state == Blocked || thrd->state == Start ) assertf( thrd->preempted == __NO_PREEMPTION,
539                                        "Error inactive thread marked as preempted, state %d, preemption %d\n", thrd->state, thrd->preempted );
540        /* paranoid */  if( thrd->preempted != __NO_PREEMPTION ) assertf(thrd->state == Active,
541                                        "Error preempted thread marked as not currently running, state %d, preemption %d\n", thrd->state, thrd->preempted );
542        /* paranoid */ #endif
543        /* paranoid */ verifyf( thrd->link.next == 0p, "Expected null got %p", thrd->link.next );
544        /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd->canary );
545
546        const bool local = thrd->state != Start;
547        if (thrd->preempted == __NO_PREEMPTION) thrd->state = Ready;
548
549        // Dereference the thread now because once we push it, there is not guaranteed it's still valid.
550        struct cluster * cl = thrd->curr_cluster;
551        __STATS(bool outside = thrd->last_proc && thrd->last_proc != kernelTLS().this_processor; )
552
553        // push the thread to the cluster ready-queue
554        push( cl, thrd, local );
555
556        // variable thrd is no longer safe to use
557        thrd = 0xdeaddeaddeaddeadp;
558
559        // wake the cluster using the save variable.
560        __wake_one( cl );
561
562        #if !defined(__CFA_NO_STATISTICS__)
563                if( kernelTLS().this_stats ) {
564                        __tls_stats()->ready.threads.threads++;
565                        if(outside) {
566                                __tls_stats()->ready.threads.extunpark++;
567                        }
568                        __push_stat( __tls_stats(), __tls_stats()->ready.threads.threads, false, "Processor", kernelTLS().this_processor );
569                }
570                else {
571                        __atomic_fetch_add(&cl->stats->ready.threads.threads, 1, __ATOMIC_RELAXED);
572                        __atomic_fetch_add(&cl->stats->ready.threads.extunpark, 1, __ATOMIC_RELAXED);
573                        __push_stat( cl->stats, cl->stats->ready.threads.threads, true, "Cluster", cl );
574                }
575        #endif
576
577        /* paranoid */ verify( ready_schedule_islocked());
578        /* paranoid */ verify( ! __preemption_enabled() );
579}
580
581void schedule_thread$( $thread * thrd ) {
582        ready_schedule_lock();
583                __schedule_thread( thrd );
584        ready_schedule_unlock();
585}
586
587// KERNEL ONLY
588static inline $thread * __next_thread(cluster * this) with( *this ) {
589        /* paranoid */ verify( ! __preemption_enabled() );
590
591        ready_schedule_lock();
592                $thread * thrd = pop_fast( this );
593        ready_schedule_unlock();
594
595        /* paranoid */ verify( ! __preemption_enabled() );
596        return thrd;
597}
598
599// KERNEL ONLY
600static inline $thread * __next_thread_slow(cluster * this) with( *this ) {
601        /* paranoid */ verify( ! __preemption_enabled() );
602
603        ready_schedule_lock();
604                $thread * thrd;
605                for(25) {
606                        thrd = pop_slow( this );
607                        if(thrd) goto RET;
608                }
609                thrd = pop_search( this );
610
611                RET:
612        ready_schedule_unlock();
613
614        /* paranoid */ verify( ! __preemption_enabled() );
615        return thrd;
616}
617
618static inline bool __must_unpark( $thread * thrd ) {
619        int old_ticket = __atomic_fetch_add(&thrd->ticket, 1, __ATOMIC_SEQ_CST);
620        switch(old_ticket) {
621                case TICKET_RUNNING:
622                        // Wake won the race, the thread will reschedule/rerun itself
623                        return false;
624                case TICKET_BLOCKED:
625                        /* paranoid */ verify( ! thrd->preempted != __NO_PREEMPTION );
626                        /* paranoid */ verify( thrd->state == Blocked );
627                        return true;
628                default:
629                        // This makes no sense, something is wrong abort
630                        abort("Thread %p (%s) has mismatch park/unpark\n", thrd, thrd->self_cor.name);
631        }
632}
633
634void __kernel_unpark( $thread * thrd ) {
635        /* paranoid */ verify( ! __preemption_enabled() );
636        /* paranoid */ verify( ready_schedule_islocked());
637
638        if( !thrd ) return;
639
640        if(__must_unpark(thrd)) {
641                // Wake lost the race,
642                __schedule_thread( thrd );
643        }
644
645        /* paranoid */ verify( ready_schedule_islocked());
646        /* paranoid */ verify( ! __preemption_enabled() );
647}
648
649void unpark( $thread * thrd ) {
650        if( !thrd ) return;
651
652        if(__must_unpark(thrd)) {
653                disable_interrupts();
654                        // Wake lost the race,
655                        schedule_thread$( thrd );
656                enable_interrupts(false);
657        }
658}
659
660void park( void ) {
661        __disable_interrupts_checked();
662                /* paranoid */ verify( kernelTLS().this_thread->preempted == __NO_PREEMPTION );
663                returnToKernel();
664        __enable_interrupts_checked();
665
666}
667
668extern "C" {
669        // Leave the thread monitor
670        // last routine called by a thread.
671        // Should never return
672        void __cfactx_thrd_leave() {
673                $thread * thrd = active_thread();
674                $monitor * this = &thrd->self_mon;
675
676                // Lock the monitor now
677                lock( this->lock __cfaabi_dbg_ctx2 );
678
679                disable_interrupts();
680
681                /* paranoid */ verify( ! __preemption_enabled() );
682                /* paranoid */ verify( thrd->state == Active );
683                /* paranoid */ verify( 0x0D15EA5E0D15EA5Ep == thrd->canary );
684                /* paranoid */ verify( kernelTLS().this_thread == thrd );
685                /* paranoid */ verify( thrd->context.SP );
686                /* 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 );
687                /* 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 );
688
689                thrd->state = Halting;
690                if( TICKET_RUNNING != thrd->ticket ) { abort( "Thread terminated with pending unpark" ); }
691                if( thrd != this->owner ) { abort( "Thread internal monitor has incorrect owner" ); }
692                if( this->recursion != 1) { abort( "Thread internal monitor has unbalanced recursion" ); }
693
694                // Leave the thread
695                returnToKernel();
696
697                // Control flow should never reach here!
698                abort();
699        }
700}
701
702// KERNEL ONLY
703bool force_yield( __Preemption_Reason reason ) {
704        __disable_interrupts_checked();
705                $thread * thrd = kernelTLS().this_thread;
706                /* paranoid */ verify(thrd->state == Active);
707
708                // SKULLDUGGERY: It is possible that we are preempting this thread just before
709                // it was going to park itself. If that is the case and it is already using the
710                // intrusive fields then we can't use them to preempt the thread
711                // If that is the case, abandon the preemption.
712                bool preempted = false;
713                if(thrd->link.next == 0p) {
714                        preempted = true;
715                        thrd->preempted = reason;
716                        returnToKernel();
717                }
718        __enable_interrupts_checked( false );
719        return preempted;
720}
721
722//=============================================================================================
723// Kernel Idle Sleep
724//=============================================================================================
725// Wake a thread from the front if there are any
726static void __wake_one(cluster * this) {
727        /* paranoid */ verify( ! __preemption_enabled() );
728        /* paranoid */ verify( ready_schedule_islocked() );
729
730        // Check if there is a sleeping processor
731        processor * p;
732        unsigned idle;
733        unsigned total;
734        [idle, total, p] = query_idles(this->procs);
735
736        // If no one is sleeping, we are done
737        if( idle == 0 ) return;
738
739        // We found a processor, wake it up
740        eventfd_t val;
741        val = 1;
742        eventfd_write( p->idle, val );
743
744        #if !defined(__CFA_NO_STATISTICS__)
745                if( kernelTLS().this_stats ) {
746                        __tls_stats()->ready.sleep.wakes++;
747                }
748                else {
749                        __atomic_fetch_add(&this->stats->ready.sleep.wakes, 1, __ATOMIC_RELAXED);
750                }
751        #endif
752
753        /* paranoid */ verify( ready_schedule_islocked() );
754        /* paranoid */ verify( ! __preemption_enabled() );
755
756        return;
757}
758
759// Unconditionnaly wake a thread
760void __wake_proc(processor * this) {
761        __cfadbg_print_safe(runtime_core, "Kernel : waking Processor %p\n", this);
762
763        __disable_interrupts_checked();
764                /* paranoid */ verify( ! __preemption_enabled() );
765                eventfd_t val;
766                val = 1;
767                eventfd_write( this->idle, val );
768        __enable_interrupts_checked();
769}
770
771static void mark_idle(__cluster_proc_list & this, processor & proc) {
772        /* paranoid */ verify( ! __preemption_enabled() );
773        lock( this );
774                this.idle++;
775                /* paranoid */ verify( this.idle <= this.total );
776                remove(proc);
777                insert_first(this.idles, proc);
778        unlock( this );
779        /* paranoid */ verify( ! __preemption_enabled() );
780}
781
782static void mark_awake(__cluster_proc_list & this, processor & proc) {
783        /* paranoid */ verify( ! __preemption_enabled() );
784        lock( this );
785                this.idle--;
786                /* paranoid */ verify( this.idle >= 0 );
787                remove(proc);
788                insert_last(this.actives, proc);
789        unlock( this );
790        /* paranoid */ verify( ! __preemption_enabled() );
791}
792
793static [unsigned idle, unsigned total, * processor] query_idles( & __cluster_proc_list this ) {
794        /* paranoid */ verify( ! __preemption_enabled() );
795        /* paranoid */ verify( ready_schedule_islocked() );
796
797        for() {
798                uint64_t l = __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST);
799                if( 1 == (l % 2) ) { Pause(); continue; }
800                unsigned idle    = this.idle;
801                unsigned total   = this.total;
802                processor * proc = &this.idles`first;
803                // Compiler fence is unnecessary, but gcc-8 and older incorrectly reorder code without it
804                asm volatile("": : :"memory");
805                if(l != __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST)) { Pause(); continue; }
806                return [idle, total, proc];
807        }
808
809        /* paranoid */ verify( ready_schedule_islocked() );
810        /* paranoid */ verify( ! __preemption_enabled() );
811}
812
813//=============================================================================================
814// Unexpected Terminating logic
815//=============================================================================================
816void __kernel_abort_msg( char * abort_text, int abort_text_size ) {
817        $thread * thrd = __cfaabi_tls.this_thread;
818
819        if(thrd) {
820                int len = snprintf( abort_text, abort_text_size, "Error occurred while executing thread %.256s (%p)", thrd->self_cor.name, thrd );
821                __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
822
823                if ( &thrd->self_cor != thrd->curr_cor ) {
824                        len = snprintf( abort_text, abort_text_size, " in coroutine %.256s (%p).\n", thrd->curr_cor->name, thrd->curr_cor );
825                        __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
826                }
827                else {
828                        __cfaabi_bits_write( STDERR_FILENO, ".\n", 2 );
829                }
830        }
831        else {
832                int len = snprintf( abort_text, abort_text_size, "Error occurred outside of any thread.\n" );
833                __cfaabi_bits_write( STDERR_FILENO, abort_text, len );
834        }
835}
836
837int __kernel_abort_lastframe( void ) __attribute__ ((__nothrow__)) {
838        return get_coroutine(__cfaabi_tls.this_thread) == get_coroutine(mainThread) ? 4 : 2;
839}
840
841static __spinlock_t kernel_debug_lock;
842
843extern "C" {
844        void __cfaabi_bits_acquire() {
845                lock( kernel_debug_lock __cfaabi_dbg_ctx2 );
846        }
847
848        void __cfaabi_bits_release() {
849                unlock( kernel_debug_lock );
850        }
851}
852
853//=============================================================================================
854// Kernel Utilities
855//=============================================================================================
856#if defined(CFA_HAVE_LINUX_IO_URING_H)
857#include "io/types.hfa"
858#endif
859
860static inline bool __maybe_io_drain( processor * proc ) {
861        bool ret = false;
862        #if defined(CFA_HAVE_LINUX_IO_URING_H)
863                __cfadbg_print_safe(runtime_core, "Kernel : core %p checking io for ring %d\n", proc, proc->io.ctx->fd);
864
865                // Check if we should drain the queue
866                $io_context * ctx = proc->io.ctx;
867                unsigned head = *ctx->cq.head;
868                unsigned tail = *ctx->cq.tail;
869                if(head == tail) return false;
870                #if OLD_MAIN
871                ready_schedule_lock();
872                ret = __cfa_io_drain( proc );
873                ready_schedule_unlock();
874                #else
875                        ret = __cfa_io_drain( proc );
876        #endif
877        #endif
878        return ret;
879}
880
881//-----------------------------------------------------------------------------
882// Debug
883__cfaabi_dbg_debug_do(
884        extern "C" {
885                void __cfaabi_dbg_record_lock(__spinlock_t & this, const char prev_name[]) {
886                        this.prev_name = prev_name;
887                        this.prev_thrd = kernelTLS().this_thread;
888                }
889        }
890)
891
892//-----------------------------------------------------------------------------
893// Debug
894bool threading_enabled(void) __attribute__((const)) {
895        return true;
896}
897
898//-----------------------------------------------------------------------------
899// Statistics
900#if !defined(__CFA_NO_STATISTICS__)
901        void print_halts( processor & this ) {
902                this.print_halts = true;
903        }
904
905        static void crawl_list( cluster * cltr, dlist(processor) & list, unsigned count ) {
906                /* paranoid */ verify( cltr->stats );
907
908                processor * it = &list`first;
909                for(unsigned i = 0; i < count; i++) {
910                        /* paranoid */ verifyf( it, "Unexpected null iterator, at index %u of %u\n", i, count);
911                        /* paranoid */ verify( it->local_data->this_stats );
912                        __tally_stats( cltr->stats, it->local_data->this_stats );
913                        it = &(*it)`next;
914                }
915        }
916
917        void crawl_cluster_stats( cluster & this ) {
918                // Stop the world, otherwise stats could get really messed-up
919                // this doesn't solve all problems but does solve many
920                // so it's probably good enough
921                uint_fast32_t last_size = ready_mutate_lock();
922
923                        crawl_list(&this, this.procs.actives, this.procs.total - this.procs.idle);
924                        crawl_list(&this, this.procs.idles  , this.procs.idle );
925
926                // Unlock the RWlock
927                ready_mutate_unlock( last_size );
928        }
929
930
931        void print_stats_now( cluster & this, int flags ) {
932                crawl_cluster_stats( this );
933                __print_stats( this.stats, this.print_stats, "Cluster", this.name, (void*)&this );
934        }
935#endif
936// Local Variables: //
937// mode: c //
938// tab-width: 4 //
939// End: //
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