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fwd.hfa @ b200492

ADTast-experimentalenumforall-pointer-decaypthread-emulationqualifiedEnum

Last change on this file since b200492 was 5d1ebb9, checked in by Peter A. Buhr <pabuhr@…>, 3 years ago
remove thread_rand, remove consolidated random generators
Property mode set to `100644`
File size: 12.1 KB

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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	/* paranoid */ verify( expected == 0p );
203	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
204	park();
205	/* paranoid */ verify( this.ptr == 1p );
206	return true;
207	}
208	}
209	}
210
211	// Mark as fulfilled, wake thread if needed
212	// return true if a thread was unparked
213	thread$ * post(oneshot & this, bool do_unpark = true) {
214	struct thread$ * got = __atomic_exchange_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
215	if( got == 0p ) return 0p;
216	if(do_unpark) unpark( got );
217	return got;
218	}
219	}
220
221	// base types for future to build upon
222	// It is based on the 'oneshot' type to allow multiple futures
223	// to block on the same instance, permitting users to block a single
224	// thread on "any of" [a given set of] futures.
225	// does not support multiple threads waiting on the same future
226	struct future_t {
227	// Internal state :
228	// 0p : is initial state (wait will block)
229	// 1p : fulfilled (wait won't block)
230	// 2p : in progress ()
231	// 3p : abandoned, server should delete
232	// any oneshot : a context has been setup to wait, a thread could wait on it
233	struct oneshot * volatile ptr;
234	};
235
236	static inline {
237	void ?{}(future_t & this) {
238	this.ptr = 0p;
239	}
240
241	void ^?{}(future_t &) {}
242
243	void reset(future_t & this) {
244	// needs to be in 0p or 1p
245	__atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
246	}
247
248	// check if the future is available
249	bool available( future_t & this ) {
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 );
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	/* paranoid */ verify( expected == 0p );
265	if(__atomic_compare_exchange_n(&this.ptr, &expected, &wait_ctx, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
266	return true;
267	}
268	}
269	}
270
271	// Stop waiting on a future
272	// When multiple futures are waited for together in "any of" pattern
273	// futures that weren't fulfilled before the thread woke up
274	// should retract the wait ctx
275	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
276	void retract( future_t & this, oneshot & wait_ctx ) {
277	// Remove the wait context
278	struct oneshot * got = __atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
279
280	// got == 0p: future was never actually setup, just return
281	if( got == 0p ) return;
282
283	// got == wait_ctx: since fulfil does an atomic_swap,
284	// if we got back the original then no one else saw context
285	// It is safe to delete (which could happen after the return)
286	if( got == &wait_ctx ) return;
287
288	// got == 1p: the future is ready and the context was fully consumed
289	// the server won't use the pointer again
290	// It is safe to delete (which could happen after the return)
291	if( got == 1p ) return;
292
293	// got == 2p: the future is ready but the context hasn't fully been consumed
294	// spin until it is safe to move on
295	if( got == 2p ) {
296	while( this.ptr != 1p ) Pause();
297	return;
298	}
299
300	// got == any thing else, something wen't wrong here, abort
301	abort("Future in unexpected state");
302	}
303
304	// Mark the future as abandoned, meaning it will be deleted by the server
305	bool abandon( future_t & this ) {
306	/* paranoid */ verify( this.ptr != 3p );
307
308	// Mark the future as abandonned
309	struct oneshot * got = __atomic_exchange_n( &this.ptr, 3p, __ATOMIC_SEQ_CST);
310
311	// If the future isn't already fulfilled, let the server delete it
312	if( got == 0p ) return false;
313
314	// got == 2p: the future is ready but the context hasn't fully been consumed
315	// spin until it is safe to move on
316	if( got == 2p ) {
317	while( this.ptr != 1p ) Pause();
318	got = 1p;
319	}
320
321	// The future is completed delete it now
322	/* paranoid */ verify( this.ptr != 1p );
323	free( &this );
324	return true;
325	}
326
327	// from the server side, mark the future as fulfilled
328	// delete it if needed
329	thread$ * fulfil( future_t & this, bool do_unpark = true ) {
330	for() {
331	struct oneshot * expected = this.ptr;
332	// was this abandoned?
333	#if defined(__GNUC__) && __GNUC__ >= 7
334	#pragma GCC diagnostic push
335	#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
336	#endif
337	if( expected == 3p ) { free( &this ); return 0p; }
338	#if defined(__GNUC__) && __GNUC__ >= 7
339	#pragma GCC diagnostic pop
340	#endif
341
342	/* paranoid */ verify( expected != 1p ); // Future is already fulfilled, should not happen
343	/* paranoid */ verify( expected != 2p ); // Future is bein fulfilled by someone else, this is even less supported then the previous case.
344
345	// If there is a wait context, we need to consume it and mark it as consumed after
346	// If there is no context then we can skip the in progress phase
347	struct oneshot * want = expected == 0p ? 1p : 2p;
348	if(__atomic_compare_exchange_n(&this.ptr, &expected, want, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
349	if( expected == 0p ) { /* paranoid */ verify( this.ptr == 1p); return 0p; }
350	thread$ * ret = post( *expected, do_unpark );
351	__atomic_store_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
352	return ret;
353	}
354	}
355
356	}
357
358	// Wait for the future to be fulfilled
359	bool wait( future_t & this ) {
360	oneshot temp;
361	if( !setup(this, temp) ) return false;
362
363	// Wait context is setup, just wait on it
364	bool ret = wait( temp );
365
366	// Wait for the future to tru
367	while( this.ptr == 2p ) Pause();
368	// Make sure the state makes sense
369	// Should be fulfilled, could be in progress but it's out of date if so
370	// since if that is the case, the oneshot was fulfilled (unparking this thread)
371	// and the oneshot should not be needed any more
372	__attribute__((unused)) struct oneshot * was = this.ptr;
373	/* paranoid */ verifyf( was == 1p, "Expected this.ptr to be 1p, was %p\n", was );
374
375	// Mark the future as fulfilled, to be consistent
376	// with potential calls to avail
377	// this.ptr = 1p;
378	return ret;
379	}
380	}
381
382	//-----------------------------------------------------------------------
383	// Statics call at the end of each thread to register statistics
384	#if !defined(__CFA_NO_STATISTICS__)
385	static inline struct __stats_t * __tls_stats() {
386	/* paranoid */ verify( ! __preemption_enabled() );
387	/* paranoid */ verify( kernelTLS().this_stats );
388	return kernelTLS().this_stats;
389	}
390
391	#define __STATS__(in_kernel, ...) { \
392	if( !(in_kernel) ) disable_interrupts(); \
393	with( *__tls_stats() ) { \
394	__VA_ARGS__ \
395	} \
396	if( !(in_kernel) ) enable_interrupts(); \
397	}
398	#else
399	#define __STATS__(in_kernel, ...)
400	#endif
401	}
402	}
403	#endif

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