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fwd.hfa @ 7ce8873

ADTast-experimentalpthread-emulation

Last change on this file since 7ce8873 was fc2c57a9, checked in by Thierry Delisle <tdelisle@…>, 23 months ago
Fixed assert in waitctx. Removed unnecessary loop in retract.
Property mode set to `100644`
File size: 13.1 KB

Line
1	//
2	// Cforall Version 1.0.0 Copyright (C) 2020 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/fwd.hfa -- PUBLIC
8	// Fundamental code needed to implement threading M.E.S. algorithms.
9	//
10	// Author : Thierry Delisle
11	// Created On : Thu Jul 30 16:46:41 2020
12	// Last Modified By :
13	// Last Modified On :
14	// Update Count :
15	//
16
17	#pragma once
18
19	#include "bits/defs.hfa"
20	#include "bits/debug.hfa"
21
22	#ifdef __cforall
23	#include "bits/random.hfa"
24	#endif
25
26	struct thread$;
27	struct processor;
28	struct cluster;
29
30	enum __Preemption_Reason { __NO_PREEMPTION, __ALARM_PREEMPTION, __POLL_PREEMPTION, __MANUAL_PREEMPTION };
31
32	#define KERNEL_STORAGE(T,X) __attribute((aligned(__alignof__(T)))) static char storage_##X[sizeof(T)]
33
34	#ifdef __cforall
35	extern "C" {
36	extern "Cforall" {
37	extern __attribute__((aligned(128))) thread_local struct KernelThreadData {
38	struct thread$ * volatile this_thread;
39	struct processor * volatile this_processor;
40	volatile bool sched_lock;
41
42	struct {
43	volatile unsigned short disable_count;
44	volatile bool enabled;
45	volatile bool in_progress;
46	} preemption_state;
47
48	#if defined(__SIZEOF_INT128__)
49	__uint128_t rand_seed;
50	#else
51	uint64_t rand_seed;
52	#endif
53	struct {
54	uint64_t fwd_seed;
55	uint64_t bck_seed;
56	} ready_rng;
57
58	struct __stats_t * volatile this_stats;
59
60
61	#ifdef __CFA_WITH_VERIFY__
62	// Debug, check if the rwlock is owned for reading
63	bool in_sched_lock;
64	unsigned sched_id;
65	#endif
66	} __cfaabi_tls __attribute__ ((tls_model ( "initial-exec" )));
67
68	extern bool __preemption_enabled();
69
70	static inline KernelThreadData & kernelTLS( void ) {
71	/* paranoid */ verify( ! __preemption_enabled() );
72	return __cfaabi_tls;
73	}
74
75	extern uintptr_t __cfatls_get( unsigned long int member );
76	#define publicTLS_get( member ) ((typeof(__cfaabi_tls.member))__cfatls_get( __builtin_offsetof(KernelThreadData, member) ))
77
78	static inline uint64_t __tls_rand() {
79	return
80	#if defined(__SIZEOF_INT128__)
81	lehmer64( kernelTLS().rand_seed );
82	#else
83	xorshift_13_7_17( kernelTLS().rand_seed );
84	#endif
85	}
86
87	static inline unsigned __tls_rand_fwd() {
88	return LCGBI_fwd( kernelTLS().ready_rng.fwd_seed );
89	}
90
91	static inline unsigned __tls_rand_bck() {
92	return LCGBI_bck( kernelTLS().ready_rng.bck_seed );
93	}
94
95	static inline void __tls_rand_advance_bck(void) {
96	kernelTLS().ready_rng.bck_seed = kernelTLS().ready_rng.fwd_seed;
97	}
98	}
99
100	extern void disable_interrupts();
101	extern void enable_interrupts( bool poll = false );
102
103	extern "Cforall" {
104	enum unpark_hint { UNPARK_LOCAL, UNPARK_REMOTE };
105
106	extern void park( void );
107	extern void unpark( struct thread$ *, unpark_hint );
108	static inline void unpark( struct thread$ * thrd ) { unpark(thrd, UNPARK_LOCAL); }
109	static inline struct thread$ * active_thread () {
110	struct thread$ * t = publicTLS_get( this_thread );
111	/* paranoid */ verify( t );
112	return t;
113	}
114
115	extern bool force_yield( enum __Preemption_Reason );
116
117	static inline void yield() {
118	force_yield(__MANUAL_PREEMPTION);
119	}
120
121	// Yield: yield N times
122	static inline void yield( unsigned times ) {
123	for( times ) {
124	yield();
125	}
126	}
127
128	// Semaphore which only supports a single thread
129	struct single_sem {
130	struct thread$ * volatile ptr;
131	};
132
133	static inline {
134	void ?{}(single_sem & this) {
135	this.ptr = 0p;
136	}
137
138	void ^?{}(single_sem &) {}
139
140	bool wait(single_sem & this) {
141	for() {
142	struct thread$ * expected = this.ptr;
143	if(expected == 1p) {
144	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
145	return false;
146	}
147	}
148	else {
149	/* paranoid */ verify( expected == 0p );
150	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
151	park();
152	return true;
153	}
154	}
155
156	}
157	}
158
159	bool post(single_sem & this) {
160	for() {
161	struct thread$ * expected = this.ptr;
162	if(expected == 1p) return false;
163	if(expected == 0p) {
164	if(__atomic_compare_exchange_n(&this.ptr, &expected, 1p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
165	return false;
166	}
167	}
168	else {
169	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
170	unpark( expected );
171	return true;
172	}
173	}
174	}
175	}
176	}
177
178	// Synchronozation primitive which only supports a single thread and one post
179	// Similar to a binary semaphore with a 'one shot' semantic
180	// is expected to be discarded after each party call their side
181	struct oneshot {
182	// Internal state :
183	// 0p : is initial state (wait will block)
184	// 1p : fulfilled (wait won't block)
185	// any thread : a thread is currently waiting
186	struct thread$ * volatile ptr;
187	};
188
189	static inline {
190	void ?{}(oneshot & this) {
191	this.ptr = 0p;
192	}
193
194	void ^?{}(oneshot &) {}
195
196	// Wait for the post, return immidiately if it already happened.
197	// return true if the thread was parked
198	bool wait(oneshot & this) {
199	for() {
200	struct thread$ * expected = this.ptr;
201	if(expected == 1p) return false;
202	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
203	park();
204	/* paranoid */ verify( this.ptr == 1p );
205	return true;
206	}
207	}
208	}
209
210	// Mark as fulfilled, wake thread if needed
211	// return true if a thread was unparked
212	thread$ * post(oneshot & this, bool do_unpark = true) {
213	struct thread$ * got = __atomic_exchange_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
214	if( got == 0p \|\| got == 1p ) return 0p;
215	if(do_unpark) unpark( got );
216	return got;
217	}
218	}
219
220	// base types for future to build upon
221	// It is based on the 'oneshot' type to allow multiple futures
222	// to block on the same instance, permitting users to block a single
223	// thread on "any of" [a given set of] futures.
224	// does not support multiple threads waiting on the same future
225	struct future_t {
226	// Internal state :
227	// 0p : is initial state (wait will block)
228	// 1p : fulfilled (wait won't block)
229	// 2p : in progress ()
230	// 3p : abandoned, server should delete
231	// any oneshot : a context has been setup to wait, a thread could wait on it
232	struct oneshot * volatile ptr;
233	};
234
235	static inline {
236	void ?{}(future_t & this) {
237	this.ptr = 0p;
238	}
239
240	void ^?{}(future_t &) {}
241
242	void reset(future_t & this) {
243	// needs to be in 0p or 1p
244	__atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
245	}
246
247	// check if the future is available
248	bool available( future_t & this ) {
249	while( this.ptr == 2p ) Pause();
250	return this.ptr == 1p;
251	}
252
253	// Prepare the future to be waited on
254	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
255	bool setup( future_t & this, oneshot & wait_ctx ) {
256	/* paranoid */ verify( wait_ctx.ptr == 0p \|\| wait_ctx.ptr == 1p );
257	// The future needs to set the wait context
258	for() {
259	struct oneshot * expected = this.ptr;
260	// Is the future already fulfilled?
261	if(expected == 1p) return false; // Yes, just return false (didn't block)
262
263	// The future is not fulfilled, try to setup the wait context
264	if(__atomic_compare_exchange_n(&this.ptr, &expected, &wait_ctx, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
265	return true;
266	}
267	}
268	}
269
270	// Stop waiting on a future
271	// When multiple futures are waited for together in "any of" pattern
272	// futures that weren't fulfilled before the thread woke up
273	// should retract the wait ctx
274	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
275	bool retract( future_t & this, oneshot & wait_ctx ) {
276	struct oneshot * expected = this.ptr;
277
278	// attempt to remove the context so it doesn't get consumed.
279	if(__atomic_compare_exchange_n( &this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
280	// we still have the original context, then no one else saw it
281	return false;
282	}
283
284	// expected == 0p: future was never actually setup, just return
285	if( expected == 0p ) return false;
286
287	// expected == 1p: the future is ready and the context was fully consumed
288	// the server won't use the pointer again
289	// It is safe to delete (which could happen after the return)
290	if( expected == 1p ) return true;
291
292	// expected == 2p: the future is ready but the context hasn't fully been consumed
293	// spin until it is safe to move on
294	if( expected == 2p ) {
295	while( this.ptr != 1p ) Pause();
296	/* paranoid */ verify( this.ptr == 1p );
297	return true;
298	}
299
300	// anything else: the future was setup with a different context ?!?!
301	// something went wrong here, abort
302	abort("Future in unexpected state");
303	}
304
305	// Mark the future as abandoned, meaning it will be deleted by the server
306	bool abandon( future_t & this ) {
307	/* paranoid */ verify( this.ptr != 3p );
308
309	// Mark the future as abandonned
310	struct oneshot * got = __atomic_exchange_n( &this.ptr, 3p, __ATOMIC_SEQ_CST);
311
312	// If the future isn't already fulfilled, let the server delete it
313	if( got == 0p ) return false;
314
315	// got == 2p: the future is ready but the context hasn't fully been consumed
316	// spin until it is safe to move on
317	if( got == 2p ) {
318	while( this.ptr != 1p ) Pause();
319	got = 1p;
320	}
321
322	// The future is completed delete it now
323	/* paranoid */ verify( this.ptr != 1p );
324	free( &this );
325	return true;
326	}
327
328	// from the server side, mark the future as fulfilled
329	// delete it if needed
330	thread$ * fulfil( future_t & this, bool do_unpark = true ) {
331	for() {
332	struct oneshot * expected = this.ptr;
333	// was this abandoned?
334	#if defined(__GNUC__) && __GNUC__ >= 7
335	#pragma GCC diagnostic push
336	#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
337	#endif
338	if( expected == 3p ) { free( &this ); return 0p; }
339	#if defined(__GNUC__) && __GNUC__ >= 7
340	#pragma GCC diagnostic pop
341	#endif
342
343	/* paranoid */ verify( expected != 1p ); // Future is already fulfilled, should not happen
344	/* paranoid */ verify( expected != 2p ); // Future is bein fulfilled by someone else, this is even less supported then the previous case.
345
346	// If there is a wait context, we need to consume it and mark it as consumed after
347	// If there is no context then we can skip the in progress phase
348	struct oneshot * want = expected == 0p ? 1p : 2p;
349	if(__atomic_compare_exchange_n(&this.ptr, &expected, want, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
350	if( expected == 0p ) { return 0p; }
351	thread$ * ret = post( *expected, do_unpark );
352	__atomic_store_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
353	return ret;
354	}
355	}
356
357	}
358
359	// Wait for the future to be fulfilled
360	bool wait( future_t & this ) {
361	oneshot temp;
362	if( !setup(this, temp) ) return false;
363
364	// Wait context is setup, just wait on it
365	bool ret = wait( temp );
366
367	// Wait for the future to tru
368	while( this.ptr == 2p ) Pause();
369	// Make sure the state makes sense
370	// Should be fulfilled, could be in progress but it's out of date if so
371	// since if that is the case, the oneshot was fulfilled (unparking this thread)
372	// and the oneshot should not be needed any more
373	__attribute__((unused)) struct oneshot * was = this.ptr;
374	/* paranoid */ verifyf( was == 1p, "Expected this.ptr to be 1p, was %p\n", was );
375
376	// Mark the future as fulfilled, to be consistent
377	// with potential calls to avail
378	// this.ptr = 1p;
379	return ret;
380	}
381
382	// Wait for any future to be fulfilled
383	forall(T& \| sized(T) \| { bool setup( T&, oneshot & ); bool retract( T&, oneshot & ); })
384	T & wait_any( T * futures, size_t num_futures ) {
385	oneshot temp;
386
387	// setup all futures
388	// if any are already satisfied return
389	for ( i; num_futures ) {
390	if( !setup(futures[i], temp) ) return futures[i];
391	}
392
393	// Wait context is setup, just wait on it
394	wait( temp );
395
396	size_t ret;
397	// attempt to retract all futures
398	for ( i; num_futures ) {
399	if ( retract( futures[i], temp ) ) ret = i;
400	}
401
402	return futures[ret];
403	}
404	}
405
406	//-----------------------------------------------------------------------
407	// Statics call at the end of each thread to register statistics
408	#if !defined(__CFA_NO_STATISTICS__)
409	static inline struct __stats_t * __tls_stats() {
410	/* paranoid */ verify( ! __preemption_enabled() );
411	/* paranoid */ verify( kernelTLS().this_stats );
412	return kernelTLS().this_stats;
413	}
414
415	#define __STATS__(in_kernel, ...) { \
416	if( !(in_kernel) ) disable_interrupts(); \
417	with( *__tls_stats() ) { \
418	__VA_ARGS__ \
419	} \
420	if( !(in_kernel) ) enable_interrupts(); \
421	}
422	#if defined(CFA_HAVE_LINUX_IO_URING_H)
423	#define __IO_STATS__(in_kernel, ...) { \
424	if( !(in_kernel) ) disable_interrupts(); \
425	with( *__tls_stats() ) { \
426	__VA_ARGS__ \
427	} \
428	if( !(in_kernel) ) enable_interrupts(); \
429	}
430	#else
431	#define __IO_STATS__(in_kernel, ...)
432	#endif
433	#else
434	#define __STATS__(in_kernel, ...)
435	#define __IO_STATS__(in_kernel, ...)
436	#endif
437	}
438	}
439	#endif

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