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kernel.cfa@ 0b18db7

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ADT arm-eh ast-experimental enum forall-pointer-decay jacob/cs343-translation new-ast-unique-expr pthread-emulation qualifiedEnum

Last change on this file since 0b18db7 was b4b63e8, checked in by Thierry Delisle <tdelisle@…>, 5 years ago
Fixed missing changes to park/unpark. Added canary to threads to check when the thread was destroyed
Property mode set to `100644`
File size: 22.2 KB

Rev	Line
[8118303]	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
[75f3522]	10	// Created On : Tue Jan 17 12:27:26 2017
[6b0b624]	11	// Last Modified By : Peter A. Buhr
[0190480]	12	// Last Modified On : Mon Aug 31 07:08:20 2020
	13	// Update Count : 71
[8118303]	14	//
	15
[2026bb6]	16	#define __cforall_thread__
[4069faad]	17	// #define __CFA_DEBUG_PRINT_RUNTIME_CORE__
[2026bb6]	18
[8118303]	19	//C Includes
[214e8da]	20	#include <errno.h>
[9d944b2]	21	#include <stdio.h>
[58b6d1b]	22	#include <signal.h>
[9d944b2]	23	#include <unistd.h>
[8118303]	24
	25	//CFA Includes
[73abe95]	26	#include "kernel_private.hfa"
	27	#include "preemption.hfa"
[8118303]	28
	29	//Private includes
	30	#define __CFA_INVOKE_PRIVATE__
	31	#include "invoke.h"
	32
[4069faad]	33
[deca0f5]	34	//-----------------------------------------------------------------------------
	35	// Some assembly required
[1805b1b]	36	#if defined( __i386 )
[deca0f5]	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
[0190480]	76	#elif defined( __arm__ )
	77	#define __x87_store
	78	#define __x87_load
	79
	80	#elif defined( __aarch64__ )
[74f5c83]	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
[deca0f5]	98	#else
[0190480]	99	#error unsupported hardware architecture
[deca0f5]	100	#endif
	101
[e660761]	102	extern $thread * mainThread;
	103	extern processor * mainProcessor;
[2ac095d]	104
[92e7631]	105	//-----------------------------------------------------------------------------
	106	// Kernel Scheduling logic
	107	static $thread * __next_thread(cluster * this);
[1eb239e4]	108	static $thread * __next_thread_slow(cluster * this);
[92e7631]	109	static void __run_thread(processor * this, $thread * dst);
[1eb239e4]	110	static void __wake_one(struct __processor_id_t * id, cluster * cltr);
	111
	112	static void push (__cluster_idles & idles, processor & proc);
	113	static void remove(__cluster_idles & idles, processor & proc);
	114	static [unsigned idle, unsigned total, * processor] query( & __cluster_idles idles );
	115
[c84e80a]	116
[75f3522]	117	//=============================================================================================
	118	// Kernel Scheduling logic
	119	//=============================================================================================
[8fcbb4c]	120	//Main of the processor contexts
[83a071f9]	121	void main(processorCtx_t & runner) {
[21184e3]	122	// Because of a bug, we couldn't initialized the seed on construction
	123	// Do it here
[7768b8d]	124	kernelTLS.rand_seed ^= rdtscl();
[f2384c9a]	125	kernelTLS.ready_rng.fwd_seed = 25214903917_l64u * (rdtscl() ^ (uintptr_t)&runner);
	126	__tls_rand_advance_bck();
[21184e3]	127
[83a071f9]	128	processor * this = runner.proc;
[094476d]	129	verify(this);
[c81ebf9]	130
[4069faad]	131	__cfadbg_print_safe(runtime_core, "Kernel : core %p starting\n", this);
[28d73c1]	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
[b798713]	137
[75f3522]	138	{
[c81ebf9]	139	// Setup preemption data
	140	preemption_scope scope = { this };
	141
[4069faad]	142	__cfadbg_print_safe(runtime_core, "Kernel : core %p started\n", this);
[8118303]	143
[ac2b598]	144	$thread * readyThread = 0p;
[1eb239e4]	145	MAIN_LOOP:
	146	for() {
[92e7631]	147	// Try to get the next thread
[8c50aed]	148	readyThread = __next_thread( this->cltr );
[75f3522]	149
[1eb239e4]	150	if( !readyThread ) {
	151	readyThread = __next_thread_slow( this->cltr );
	152	}
[4e6fb8e]	153
[1eb239e4]	154	HALT:
	155	if( !readyThread ) {
	156	// Don't block if we are done
	157	if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
[c81ebf9]	158
[1eb239e4]	159	#if !defined(__CFA_NO_STATISTICS__)
	160	__tls_stats()->ready.sleep.halts++;
	161	#endif
[398e8e9]	162
[1eb239e4]	163	// Push self to idle stack
	164	push(this->cltr->idles, * this);
[398e8e9]	165
[1eb239e4]	166	// Confirm the ready-queue is empty
	167	readyThread = __next_thread_slow( this->cltr );
	168	if( readyThread ) {
	169	// A thread was found, cancel the halt
	170	remove(this->cltr->idles, * this);
	171
	172	#if !defined(__CFA_NO_STATISTICS__)
	173	__tls_stats()->ready.sleep.cancels++;
	174	#endif
	175
	176	// continue the mai loop
	177	break HALT;
	178	}
	179
	180	#if !defined(__CFA_NO_STATISTICS__)
	181	if(this->print_halts) {
	182	__cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 0\n", this->id, rdtscl());
	183	}
	184	#endif
	185
	186	wait( this->idle );
	187
	188	#if !defined(__CFA_NO_STATISTICS__)
	189	if(this->print_halts) {
	190	__cfaabi_bits_print_safe( STDOUT_FILENO, "PH:%d - %lld 1\n", this->id, rdtscl());
	191	}
	192	#endif
	193
	194	// We were woken up, remove self from idle
	195	remove(this->cltr->idles, * this);
	196
	197	// DON'T just proceed, start looking again
	198	continue MAIN_LOOP;
[64a7146]	199	}
[1eb239e4]	200
	201	/* paranoid */ verify( readyThread );
	202
	203	// We found a thread run it
	204	__run_thread(this, readyThread);
	205
	206	// Are we done?
	207	if( __atomic_load_n(&this->do_terminate, __ATOMIC_SEQ_CST) ) break MAIN_LOOP;
[c81ebf9]	208	}
	209
[4069faad]	210	__cfadbg_print_safe(runtime_core, "Kernel : core %p stopping\n", this);
[c84e80a]	211	}
[8118303]	212
[4cedd9f]	213	V( this->terminated );
[bdeba0b]	214
[28d73c1]	215	if(this == mainProcessor) {
[6a490b2]	216	// HACK : the coroutine context switch expects this_thread to be set
	217	// and it make sense for it to be set in all other cases except here
	218	// fake it
	219	kernelTLS.this_thread = mainThread;
	220	}
[7768b8d]	221
[4069faad]	222	__cfadbg_print_safe(runtime_core, "Kernel : core %p terminated\n", this);
[c84e80a]	223	}
	224
[5c1a531]	225	static int * __volatile_errno() __attribute__((noinline));
	226	static int * __volatile_errno() { asm(""); return &errno; }
	227
[14a61b5]	228	// KERNEL ONLY
[1c273d0]	229	// runThread runs a thread by context switching
	230	// from the processor coroutine to the target thread
[ac2b598]	231	static void __run_thread(processor * this, $thread * thrd_dst) {
[1eb239e4]	232	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	233	/* paranoid */ verifyf( thrd_dst->state == Ready \|\| thrd_dst->preempted != __NO_PREEMPTION, "state : %d, preempted %d\n", thrd_dst->state, thrd_dst->preempted);
	234	/* paranoid */ verifyf( thrd_dst->link.next == 0p, "Expected null got %p", thrd_dst->link.next );
	235	__builtin_prefetch( thrd_dst->context.SP );
	236
[ac2b598]	237	$coroutine * proc_cor = get_coroutine(this->runner);
[8fcbb4c]	238
[9f575ea]	239	// set state of processor coroutine to inactive
	240	verify(proc_cor->state == Active);
[ae7be7a]	241	proc_cor->state = Blocked;
[e8e457e]	242
[9f575ea]	243	// Actually run the thread
[3381ed7]	244	RUNNING: while(true) {
[ff79d5e]	245	thrd_dst->preempted = __NO_PREEMPTION;
	246	thrd_dst->state = Active;
[e8e457e]	247
[58d64a4]	248	// Update global state
	249	kernelTLS.this_thread = thrd_dst;
[75f3522]	250
[3381ed7]	251	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[a7b486b]	252	/* paranoid */ verify( kernelTLS.this_thread == thrd_dst );
[b4b63e8]	253	/* paranoid */ verify( thrd_dst->context.SP );
[210b8b3]	254	/* 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
	255	/* 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
[b4b63e8]	256	/* paranoid */ verify( 0x0D15EA5E0D15EA5E == thrd_dst->canary );
	257
[3381ed7]	258
[58d64a4]	259
[9f575ea]	260	// set context switch to the thread that the processor is executing
[c7a900a]	261	__cfactx_switch( &proc_cor->context, &thrd_dst->context );
	262	// when __cfactx_switch returns we are back in the processor coroutine
[9f575ea]	263
[b4b63e8]	264	/* paranoid */ verify( 0x0D15EA5E0D15EA5E == thrd_dst->canary );
[210b8b3]	265	/* 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 );
	266	/* 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 );
[b4b63e8]	267	/* paranoid */ verify( thrd_dst->context.SP );
[a7b486b]	268	/* paranoid */ verify( kernelTLS.this_thread == thrd_dst );
[3381ed7]	269	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[75f3522]	270
[58d64a4]	271	// Reset global state
	272	kernelTLS.this_thread = 0p;
[3381ed7]	273
	274	// We just finished running a thread, there are a few things that could have happened.
	275	// 1 - Regular case : the thread has blocked and now one has scheduled it yet.
	276	// 2 - Racy case : the thread has blocked but someone has already tried to schedule it.
	277	// 4 - Preempted
	278	// In case 1, we may have won a race so we can't write to the state again.
	279	// In case 2, we lost the race so we now own the thread.
	280
	281	if(unlikely(thrd_dst->preempted != __NO_PREEMPTION)) {
	282	// The thread was preempted, reschedule it and reset the flag
[9b1dcc2]	283	__schedule_thread( (__processor_id_t*)this, thrd_dst );
[3381ed7]	284	break RUNNING;
	285	}
[75f3522]	286
[ff79d5e]	287	if(unlikely(thrd_dst->state == Halted)) {
	288	// The thread has halted, it should never be scheduled/run again
	289	// We may need to wake someone up here since
[e235429]	290	unpark( this->destroyer );
[ff79d5e]	291	this->destroyer = 0p;
	292	break RUNNING;
	293	}
	294
	295	/* paranoid */ verify( thrd_dst->state == Active );
	296	thrd_dst->state = Blocked;
	297
[3381ed7]	298	// set state of processor coroutine to active and the thread to inactive
[ff79d5e]	299	int old_ticket = __atomic_fetch_sub(&thrd_dst->ticket, 1, __ATOMIC_SEQ_CST);
	300	switch(old_ticket) {
	301	case 1:
[3381ed7]	302	// This is case 1, the regular case, nothing more is needed
	303	break RUNNING;
[ff79d5e]	304	case 2:
[3381ed7]	305	// This is case 2, the racy case, someone tried to run this thread before it finished blocking
	306	// In this case, just run it again.
	307	continue RUNNING;
	308	default:
	309	// This makes no sense, something is wrong abort
[ff79d5e]	310	abort();
[3381ed7]	311	}
[9f575ea]	312	}
[e8e457e]	313
[9f575ea]	314	// Just before returning to the processor, set the processor coroutine to active
[e8e457e]	315	proc_cor->state = Active;
[1eb239e4]	316
	317	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[82c948c]	318	}
	319
[14a61b5]	320	// KERNEL_ONLY
[b0c7419]	321	void returnToKernel() {
[3381ed7]	322	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[ac2b598]	323	$coroutine * proc_cor = get_coroutine(kernelTLS.this_processor->runner);
	324	$thread * thrd_src = kernelTLS.this_thread;
[e8e457e]	325
[29cb302]	326	#if !defined(__CFA_NO_STATISTICS__)
	327	struct processor * last_proc = kernelTLS.this_processor;
	328	#endif
	329
[9f575ea]	330	// Run the thread on this processor
	331	{
	332	int local_errno = *__volatile_errno();
	333	#if defined( __i386 ) \|\| defined( __x86_64 )
	334	__x87_store;
	335	#endif
[b4b63e8]	336	/* paranoid */ verify( proc_cor->context.SP );
	337	/* paranoid */ verify( 0x0D15EA5E0D15EA5E == thrd_src->canary );
[c7a900a]	338	__cfactx_switch( &thrd_src->context, &proc_cor->context );
[b4b63e8]	339	/* paranoid */ verify( 0x0D15EA5E0D15EA5E == thrd_src->canary );
[9f575ea]	340	#if defined( __i386 ) \|\| defined( __x86_64 )
	341	__x87_load;
	342	#endif
	343	*__volatile_errno() = local_errno;
[8fcbb4c]	344	}
[deca0f5]	345
[29cb302]	346	#if !defined(__CFA_NO_STATISTICS__)
	347	if(last_proc != kernelTLS.this_processor) {
	348	__tls_stats()->ready.threads.migration++;
	349	}
	350	#endif
	351
[3381ed7]	352	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[210b8b3]	353	/* 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 );
	354	/* 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 );
[c84e80a]	355	}
	356
[8def349]	357	//-----------------------------------------------------------------------------
	358	// Scheduler routines
[14a61b5]	359	// KERNEL ONLY
[9b1dcc2]	360	void __schedule_thread( struct __processor_id_t * id, $thread * thrd ) {
[6a490b2]	361	/* paranoid */ verify( thrd );
	362	/* paranoid */ verify( thrd->state != Halted );
[9f575ea]	363	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[3381ed7]	364	/* paranoid */ #if defined( __CFA_WITH_VERIFY__ )
[504a7dc]	365	/* paranoid */ if( thrd->state == Blocked \|\| thrd->state == Start ) assertf( thrd->preempted == __NO_PREEMPTION,
	366	"Error inactive thread marked as preempted, state %d, preemption %d\n", thrd->state, thrd->preempted );
[ff79d5e]	367	/* paranoid */ if( thrd->preempted != __NO_PREEMPTION ) assertf(thrd->state == Active,
[504a7dc]	368	"Error preempted thread marked as not currently running, state %d, preemption %d\n", thrd->state, thrd->preempted );
[3381ed7]	369	/* paranoid */ #endif
[6a490b2]	370	/* paranoid */ verifyf( thrd->link.next == 0p, "Expected null got %p", thrd->link.next );
[b4b63e8]	371	/* paranoid */ verify( 0x0D15EA5E0D15EA5E == thrd->canary );
	372
[9f575ea]	373
[ae7be7a]	374	if (thrd->preempted == __NO_PREEMPTION) thrd->state = Ready;
[6b4cdd3]	375
[9b1dcc2]	376	ready_schedule_lock ( id );
[504a7dc]	377	push( thrd->curr_cluster, thrd );
[1eb239e4]	378	__wake_one(id, thrd->curr_cluster);
[9b1dcc2]	379	ready_schedule_unlock( id );
[1c273d0]	380
[9f575ea]	381	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[db6f06a]	382	}
	383
[14a61b5]	384	// KERNEL ONLY
[1eb239e4]	385	static inline $thread * __next_thread(cluster * this) with( *this ) {
[3381ed7]	386	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[7768b8d]	387
[9b1dcc2]	388	ready_schedule_lock ( (__processor_id_t*)kernelTLS.this_processor );
[1eb239e4]	389	$thread * thrd = pop( this );
[9b1dcc2]	390	ready_schedule_unlock( (__processor_id_t*)kernelTLS.this_processor );
[7768b8d]	391
[3381ed7]	392	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[1eb239e4]	393	return thrd;
[eb2e723]	394	}
	395
[64a7146]	396	// KERNEL ONLY
[1eb239e4]	397	static inline $thread * __next_thread_slow(cluster * this) with( *this ) {
[64a7146]	398	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	399
	400	ready_schedule_lock ( (__processor_id_t*)kernelTLS.this_processor );
[1eb239e4]	401	$thread * thrd = pop_slow( this );
[64a7146]	402	ready_schedule_unlock( (__processor_id_t*)kernelTLS.this_processor );
	403
	404	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[1eb239e4]	405	return thrd;
[64a7146]	406	}
	407
[2d8f7b0]	408	// KERNEL ONLY unpark with out disabling interrupts
[e235429]	409	void __unpark( struct __processor_id_t * id, $thread * thrd ) {
[ff79d5e]	410	int old_ticket = __atomic_fetch_add(&thrd->ticket, 1, __ATOMIC_SEQ_CST);
	411	switch(old_ticket) {
	412	case 1:
[3381ed7]	413	// Wake won the race, the thread will reschedule/rerun itself
	414	break;
[ff79d5e]	415	case 0:
[3381ed7]	416	/* paranoid */ verify( ! thrd->preempted != __NO_PREEMPTION );
[ff79d5e]	417	/* paranoid */ verify( thrd->state == Blocked );
[0b33412]	418
[3381ed7]	419	// Wake lost the race,
[9b1dcc2]	420	__schedule_thread( id, thrd );
[3381ed7]	421	break;
	422	default:
	423	// This makes no sense, something is wrong abort
	424	abort();
[de6319f]	425	}
[db6f06a]	426	}
	427
[e235429]	428	void unpark( $thread * thrd ) {
[2d8f7b0]	429	if( !thrd ) return;
[db6f06a]	430
[82ff5845]	431	disable_interrupts();
[e235429]	432	__unpark( (__processor_id_t*)kernelTLS.this_processor, thrd );
[36982fc]	433	enable_interrupts( __cfaabi_dbg_ctx );
[eb2e723]	434	}
	435
[e235429]	436	void park( void ) {
[3381ed7]	437	/* paranoid */ verify( kernelTLS.preemption_state.enabled );
[82ff5845]	438	disable_interrupts();
[3381ed7]	439	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	440	/* paranoid */ verify( kernelTLS.this_thread->preempted == __NO_PREEMPTION );
[0b33412]	441
[82c948c]	442	returnToKernel();
[0b33412]	443
[3381ed7]	444	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[36982fc]	445	enable_interrupts( __cfaabi_dbg_ctx );
[3381ed7]	446	/* paranoid */ verify( kernelTLS.preemption_state.enabled );
[0c78741]	447
	448	}
[09800e9]	449
[3381ed7]	450	// KERNEL ONLY
[b0c7419]	451	void __leave_thread() {
[3381ed7]	452	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[09800e9]	453	returnToKernel();
[b0c7419]	454	abort();
[09800e9]	455	}
	456
[14a61b5]	457	// KERNEL ONLY
[3381ed7]	458	bool force_yield( __Preemption_Reason reason ) {
	459	/* paranoid */ verify( kernelTLS.preemption_state.enabled );
[09800e9]	460	disable_interrupts();
[3381ed7]	461	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[09800e9]	462
[ac2b598]	463	$thread * thrd = kernelTLS.this_thread;
[ff79d5e]	464	/* paranoid */ verify(thrd->state == Active);
[3381ed7]	465
	466	// SKULLDUGGERY: It is possible that we are preempting this thread just before
	467	// it was going to park itself. If that is the case and it is already using the
	468	// intrusive fields then we can't use them to preempt the thread
	469	// If that is the case, abandon the preemption.
	470	bool preempted = false;
[504a7dc]	471	if(thrd->link.next == 0p) {
[3381ed7]	472	preempted = true;
	473	thrd->preempted = reason;
	474	returnToKernel();
[de6319f]	475	}
[f2b12406]	476
[3381ed7]	477	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	478	enable_interrupts_noPoll();
	479	/* paranoid */ verify( kernelTLS.preemption_state.enabled );
[f2b12406]	480
[3381ed7]	481	return preempted;
[f2b12406]	482	}
	483
[14a61b5]	484	//=============================================================================================
[92e7631]	485	// Kernel Idle Sleep
[14a61b5]	486	//=============================================================================================
[64a7146]	487	// Wake a thread from the front if there are any
[1eb239e4]	488	static void __wake_one(struct __processor_id_t * id, cluster * this) {
	489	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[64a7146]	490	/* paranoid */ verify( ready_schedule_islocked( id ) );
[14a61b5]	491
[64a7146]	492	// Check if there is a sleeping processor
[1eb239e4]	493	processor * p;
	494	unsigned idle;
	495	unsigned total;
	496	[idle, total, p] = query(this->idles);
[14a61b5]	497
[64a7146]	498	// If no one is sleeping, we are done
[1eb239e4]	499	if( idle == 0 ) return;
[14a61b5]	500
[64a7146]	501	// We found a processor, wake it up
	502	post( p->idle );
[14a61b5]	503
[1eb239e4]	504	#if !defined(__CFA_NO_STATISTICS__)
	505	__tls_stats()->ready.sleep.wakes++;
	506	#endif
	507
	508	/* paranoid */ verify( ready_schedule_islocked( id ) );
	509	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	510
	511	return;
[64a7146]	512	}
[14a61b5]	513
[64a7146]	514	// Unconditionnaly wake a thread
[1eb239e4]	515	void __wake_proc(processor * this) {
[64a7146]	516	__cfadbg_print_safe(runtime_core, "Kernel : waking Processor %p\n", this);
[14a61b5]	517
[64a7146]	518	disable_interrupts();
	519	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
[58d64a4]	520	post( this->idle );
[64a7146]	521	enable_interrupts( __cfaabi_dbg_ctx );
[92e7631]	522	}
	523
[1eb239e4]	524	static void push (__cluster_idles & this, processor & proc) {
	525	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	526	lock( this );
	527	this.idle++;
	528	/* paranoid */ verify( this.idle <= this.total );
[8e16177]	529
[1eb239e4]	530	insert_first(this.list, proc);
	531	unlock( this );
	532	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	533	}
[8e16177]	534
[1eb239e4]	535	static void remove(__cluster_idles & this, processor & proc) {
	536	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	537	lock( this );
	538	this.idle--;
	539	/* paranoid */ verify( this.idle >= 0 );
[c34ebf2]	540
[1eb239e4]	541	remove(proc);
	542	unlock( this );
	543	/* paranoid */ verify( ! kernelTLS.preemption_state.enabled );
	544	}
[c34ebf2]	545
[1eb239e4]	546	static [unsigned idle, unsigned total, * processor] query( & __cluster_idles this ) {
	547	for() {
	548	uint64_t l = __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST);
	549	if( 1 == (l % 2) ) { Pause(); continue; }
	550	unsigned idle = this.idle;
	551	unsigned total = this.total;
	552	processor * proc = &this.list`first;
[7fdae38]	553	// Compiler fence is unnecessary, but gcc-8 and older incorrectly reorder code without it
	554	asm volatile("": : :"memory");
[1eb239e4]	555	if(l != __atomic_load_n(&this.lock, __ATOMIC_SEQ_CST)) { Pause(); continue; }
	556	return [idle, total, proc];
	557	}
[6b4cdd3]	558	}
	559
[dbe9b08]	560	//=============================================================================================
	561	// Unexpected Terminating logic
	562	//=============================================================================================
[ea7d2b0]	563	static __spinlock_t kernel_abort_lock;
[9d944b2]	564	static bool kernel_abort_called = false;
	565
[afd550c]	566	void * kernel_abort(void) __attribute__ ((__nothrow__)) {
[9d944b2]	567	// abort cannot be recursively entered by the same or different processors because all signal handlers return when
	568	// the globalAbort flag is true.
[36982fc]	569	lock( kernel_abort_lock __cfaabi_dbg_ctx2 );
[9d944b2]	570
	571	// first task to abort ?
[de94a60]	572	if ( kernel_abort_called ) { // not first task to abort ?
[ea7d2b0]	573	unlock( kernel_abort_lock );
[1c273d0]	574
[9d944b2]	575	sigset_t mask;
	576	sigemptyset( &mask );
[de94a60]	577	sigaddset( &mask, SIGALRM ); // block SIGALRM signals
[8a13c47]	578	sigaddset( &mask, SIGUSR1 ); // block SIGALRM signals
	579	sigsuspend( &mask ); // block the processor to prevent further damage during abort
	580	_exit( EXIT_FAILURE ); // if processor unblocks before it is killed, terminate it
[de94a60]	581	}
	582	else {
	583	kernel_abort_called = true;
	584	unlock( kernel_abort_lock );
[9d944b2]	585	}
	586
[14a61b5]	587	return kernelTLS.this_thread;
[9d944b2]	588	}
	589
	590	void kernel_abort_msg( void * kernel_data, char * abort_text, int abort_text_size ) {
[b81fd95]	591	$thread * thrd = ( $thread * ) kernel_data;
[9d944b2]	592
[de94a60]	593	if(thrd) {
	594	int len = snprintf( abort_text, abort_text_size, "Error occurred while executing thread %.256s (%p)", thrd->self_cor.name, thrd );
[1c40091]	595	__cfaabi_bits_write( STDERR_FILENO, abort_text, len );
[de94a60]	596
[212c2187]	597	if ( &thrd->self_cor != thrd->curr_cor ) {
	598	len = snprintf( abort_text, abort_text_size, " in coroutine %.256s (%p).\n", thrd->curr_cor->name, thrd->curr_cor );
[1c40091]	599	__cfaabi_bits_write( STDERR_FILENO, abort_text, len );
[de94a60]	600	}
	601	else {
[1c40091]	602	__cfaabi_bits_write( STDERR_FILENO, ".\n", 2 );
[de94a60]	603	}
[1c273d0]	604	}
[9d944b2]	605	else {
[de94a60]	606	int len = snprintf( abort_text, abort_text_size, "Error occurred outside of any thread.\n" );
[1c40091]	607	__cfaabi_bits_write( STDERR_FILENO, abort_text, len );
[9d944b2]	608	}
	609	}
	610
[2b8bc41]	611	int kernel_abort_lastframe( void ) __attribute__ ((__nothrow__)) {
[14a61b5]	612	return get_coroutine(kernelTLS.this_thread) == get_coroutine(mainThread) ? 4 : 2;
[2b8bc41]	613	}
	614
[de94a60]	615	static __spinlock_t kernel_debug_lock;
	616
[9d944b2]	617	extern "C" {
[1c40091]	618	void __cfaabi_bits_acquire() {
[36982fc]	619	lock( kernel_debug_lock __cfaabi_dbg_ctx2 );
[9d944b2]	620	}
	621
[1c40091]	622	void __cfaabi_bits_release() {
[ea7d2b0]	623	unlock( kernel_debug_lock );
[9d944b2]	624	}
[8118303]	625	}
	626
[fa21ac9]	627	//=============================================================================================
	628	// Kernel Utilities
	629	//=============================================================================================
[bd98b58]	630	//-----------------------------------------------------------------------------
	631	// Locks
[242a902]	632	void ?{}( semaphore & this, int count = 1 ) {
	633	(this.lock){};
	634	this.count = count;
	635	(this.waiting){};
[db6f06a]	636	}
[242a902]	637	void ^?{}(semaphore & this) {}
[db6f06a]	638
[71c8b7e]	639	bool P(semaphore & this) with( this ){
[65deb18]	640	lock( lock __cfaabi_dbg_ctx2 );
	641	count -= 1;
	642	if ( count < 0 ) {
[bdeba0b]	643	// queue current task
[14a61b5]	644	append( waiting, kernelTLS.this_thread );
[bdeba0b]	645
	646	// atomically release spin lock and block
[3381ed7]	647	unlock( lock );
[e235429]	648	park();
[71c8b7e]	649	return true;
[8def349]	650	}
[4e6fb8e]	651	else {
[65deb18]	652	unlock( lock );
[71c8b7e]	653	return false;
[4e6fb8e]	654	}
[bd98b58]	655	}
	656
[f0ce5f4]	657	bool V(semaphore & this) with( this ) {
[ac2b598]	658	$thread * thrd = 0p;
[65deb18]	659	lock( lock __cfaabi_dbg_ctx2 );
	660	count += 1;
	661	if ( count <= 0 ) {
[bdeba0b]	662	// remove task at head of waiting list
[65deb18]	663	thrd = pop_head( waiting );
[bd98b58]	664	}
[bdeba0b]	665
[65deb18]	666	unlock( lock );
[bdeba0b]	667
	668	// make new owner
[e235429]	669	unpark( thrd );
[f0ce5f4]	670
[d384787]	671	return thrd != 0p;
	672	}
	673
	674	bool V(semaphore & this, unsigned diff) with( this ) {
	675	$thread * thrd = 0p;
	676	lock( lock __cfaabi_dbg_ctx2 );
	677	int release = max(-count, (int)diff);
	678	count += diff;
	679	for(release) {
[e235429]	680	unpark( pop_head( waiting ) );
[d384787]	681	}
	682
	683	unlock( lock );
	684
[f0ce5f4]	685	return thrd != 0p;
[bd98b58]	686	}
	687
[de94a60]	688	//-----------------------------------------------------------------------------
	689	// Debug
	690	__cfaabi_dbg_debug_do(
[1997b4e]	691	extern "C" {
[ae66348]	692	void __cfaabi_dbg_record_lock(__spinlock_t & this, const char prev_name[]) {
[1997b4e]	693	this.prev_name = prev_name;
	694	this.prev_thrd = kernelTLS.this_thread;
	695	}
[9181f1d]	696	}
[f7d6bb0]	697	)
[2026bb6]	698
	699	//-----------------------------------------------------------------------------
	700	// Debug
[8c50aed]	701	bool threading_enabled(void) __attribute__((const)) {
[2026bb6]	702	return true;
	703	}
[c34ebf2]	704
	705	//-----------------------------------------------------------------------------
	706	// Statistics
	707	#if !defined(__CFA_NO_STATISTICS__)
	708	void print_halts( processor & this ) {
	709	this.print_halts = true;
	710	}
	711	#endif
[8118303]	712	// Local Variables: //
	713	// mode: c //
	714	// tab-width: 4 //
	715	// End: //

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