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fwd.hfa @ 2210cfc

ADTast-experimentalenumforall-pointer-decaypthread-emulationqualifiedEnum

Last change on this file since 2210cfc was 24e321c, checked in by Thierry Delisle <tdelisle@…>, 3 years ago
Unpark now takes a hint on locality.
Property mode set to `100644`
File size: 12.5 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	#if defined(__SIZEOF_INT128__)
80	return __lehmer64( kernelTLS().rand_seed );
81	#else
82	return __xorshift64( kernelTLS().rand_seed );
83	#endif
84	}
85
86	#define M (1_l64u << 48_l64u)
87	#define A (25214903917_l64u)
88	#define AI (18446708753438544741_l64u)
89	#define C (11_l64u)
90	#define D (16_l64u)
91
92	static inline unsigned __tls_rand_fwd() {
93
94	kernelTLS().ready_rng.fwd_seed = (A * kernelTLS().ready_rng.fwd_seed + C) & (M - 1);
95	return kernelTLS().ready_rng.fwd_seed >> D;
96	}
97
98	static inline unsigned __tls_rand_bck() {
99	unsigned int r = kernelTLS().ready_rng.bck_seed >> D;
100	kernelTLS().ready_rng.bck_seed = AI * (kernelTLS().ready_rng.bck_seed - C) & (M - 1);
101	return r;
102	}
103
104	#undef M
105	#undef A
106	#undef AI
107	#undef C
108	#undef D
109
110	static inline void __tls_rand_advance_bck(void) {
111	kernelTLS().ready_rng.bck_seed = kernelTLS().ready_rng.fwd_seed;
112	}
113	}
114
115
116
117	extern void disable_interrupts();
118	extern void enable_interrupts( bool poll = false );
119
120	extern "Cforall" {
121	enum unpark_hint { UNPARK_LOCAL, UNPARK_REMOTE };
122
123	extern void park( void );
124	extern void unpark( struct thread$ *, unpark_hint );
125	static inline void unpark( struct thread$ * thrd ) { unpark(thrd, UNPARK_LOCAL); }
126	static inline struct thread$ * active_thread () {
127	struct thread$ * t = publicTLS_get( this_thread );
128	/* paranoid */ verify( t );
129	return t;
130	}
131
132	extern bool force_yield( enum __Preemption_Reason );
133
134	static inline void yield() {
135	force_yield(__MANUAL_PREEMPTION);
136	}
137
138	// Yield: yield N times
139	static inline void yield( unsigned times ) {
140	for( times ) {
141	yield();
142	}
143	}
144
145	extern uint64_t thread_rand();
146
147	// Semaphore which only supports a single thread
148	struct single_sem {
149	struct thread$ * volatile ptr;
150	};
151
152	static inline {
153	void ?{}(single_sem & this) {
154	this.ptr = 0p;
155	}
156
157	void ^?{}(single_sem &) {}
158
159	bool wait(single_sem & this) {
160	for() {
161	struct thread$ * expected = this.ptr;
162	if(expected == 1p) {
163	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
164	return false;
165	}
166	}
167	else {
168	/* paranoid */ verify( expected == 0p );
169	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
170	park();
171	return true;
172	}
173	}
174
175	}
176	}
177
178	bool post(single_sem & this) {
179	for() {
180	struct thread$ * expected = this.ptr;
181	if(expected == 1p) return false;
182	if(expected == 0p) {
183	if(__atomic_compare_exchange_n(&this.ptr, &expected, 1p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
184	return false;
185	}
186	}
187	else {
188	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
189	unpark( expected );
190	return true;
191	}
192	}
193	}
194	}
195	}
196
197	// Synchronozation primitive which only supports a single thread and one post
198	// Similar to a binary semaphore with a 'one shot' semantic
199	// is expected to be discarded after each party call their side
200	struct oneshot {
201	// Internal state :
202	// 0p : is initial state (wait will block)
203	// 1p : fulfilled (wait won't block)
204	// any thread : a thread is currently waiting
205	struct thread$ * volatile ptr;
206	};
207
208	static inline {
209	void ?{}(oneshot & this) {
210	this.ptr = 0p;
211	}
212
213	void ^?{}(oneshot &) {}
214
215	// Wait for the post, return immidiately if it already happened.
216	// return true if the thread was parked
217	bool wait(oneshot & this) {
218	for() {
219	struct thread$ * expected = this.ptr;
220	if(expected == 1p) return false;
221	/* paranoid */ verify( expected == 0p );
222	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
223	park();
224	/* paranoid */ verify( this.ptr == 1p );
225	return true;
226	}
227	}
228	}
229
230	// Mark as fulfilled, wake thread if needed
231	// return true if a thread was unparked
232	thread$ * post(oneshot & this, bool do_unpark = true) {
233	struct thread$ * got = __atomic_exchange_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
234	if( got == 0p ) return 0p;
235	if(do_unpark) unpark( got );
236	return got;
237	}
238	}
239
240	// base types for future to build upon
241	// It is based on the 'oneshot' type to allow multiple futures
242	// to block on the same instance, permitting users to block a single
243	// thread on "any of" [a given set of] futures.
244	// does not support multiple threads waiting on the same future
245	struct future_t {
246	// Internal state :
247	// 0p : is initial state (wait will block)
248	// 1p : fulfilled (wait won't block)
249	// 2p : in progress ()
250	// 3p : abandoned, server should delete
251	// any oneshot : a context has been setup to wait, a thread could wait on it
252	struct oneshot * volatile ptr;
253	};
254
255	static inline {
256	void ?{}(future_t & this) {
257	this.ptr = 0p;
258	}
259
260	void ^?{}(future_t &) {}
261
262	void reset(future_t & this) {
263	// needs to be in 0p or 1p
264	__atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
265	}
266
267	// check if the future is available
268	bool available( future_t & this ) {
269	return this.ptr == 1p;
270	}
271
272	// Prepare the future to be waited on
273	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
274	bool setup( future_t & this, oneshot & wait_ctx ) {
275	/* paranoid */ verify( wait_ctx.ptr == 0p );
276	// The future needs to set the wait context
277	for() {
278	struct oneshot * expected = this.ptr;
279	// Is the future already fulfilled?
280	if(expected == 1p) return false; // Yes, just return false (didn't block)
281
282	// The future is not fulfilled, try to setup the wait context
283	/* paranoid */ verify( expected == 0p );
284	if(__atomic_compare_exchange_n(&this.ptr, &expected, &wait_ctx, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
285	return true;
286	}
287	}
288	}
289
290	// Stop waiting on a future
291	// When multiple futures are waited for together in "any of" pattern
292	// futures that weren't fulfilled before the thread woke up
293	// should retract the wait ctx
294	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
295	void retract( future_t & this, oneshot & wait_ctx ) {
296	// Remove the wait context
297	struct oneshot * got = __atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
298
299	// got == 0p: future was never actually setup, just return
300	if( got == 0p ) return;
301
302	// got == wait_ctx: since fulfil does an atomic_swap,
303	// if we got back the original then no one else saw context
304	// It is safe to delete (which could happen after the return)
305	if( got == &wait_ctx ) return;
306
307	// got == 1p: the future is ready and the context was fully consumed
308	// the server won't use the pointer again
309	// It is safe to delete (which could happen after the return)
310	if( got == 1p ) return;
311
312	// got == 2p: the future is ready but the context hasn't fully been consumed
313	// spin until it is safe to move on
314	if( got == 2p ) {
315	while( this.ptr != 1p ) Pause();
316	return;
317	}
318
319	// got == any thing else, something wen't wrong here, abort
320	abort("Future in unexpected state");
321	}
322
323	// Mark the future as abandoned, meaning it will be deleted by the server
324	bool abandon( future_t & this ) {
325	/* paranoid */ verify( this.ptr != 3p );
326
327	// Mark the future as abandonned
328	struct oneshot * got = __atomic_exchange_n( &this.ptr, 3p, __ATOMIC_SEQ_CST);
329
330	// If the future isn't already fulfilled, let the server delete it
331	if( got == 0p ) return false;
332
333	// got == 2p: the future is ready but the context hasn't fully been consumed
334	// spin until it is safe to move on
335	if( got == 2p ) {
336	while( this.ptr != 1p ) Pause();
337	got = 1p;
338	}
339
340	// The future is completed delete it now
341	/* paranoid */ verify( this.ptr != 1p );
342	free( &this );
343	return true;
344	}
345
346	// from the server side, mark the future as fulfilled
347	// delete it if needed
348	thread$ * fulfil( future_t & this, bool do_unpark = true ) {
349	for() {
350	struct oneshot * expected = this.ptr;
351	// was this abandoned?
352	#if defined(__GNUC__) && __GNUC__ >= 7
353	#pragma GCC diagnostic push
354	#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
355	#endif
356	if( expected == 3p ) { free( &this ); return 0p; }
357	#if defined(__GNUC__) && __GNUC__ >= 7
358	#pragma GCC diagnostic pop
359	#endif
360
361	/* paranoid */ verify( expected != 1p ); // Future is already fulfilled, should not happen
362	/* paranoid */ verify( expected != 2p ); // Future is bein fulfilled by someone else, this is even less supported then the previous case.
363
364	// If there is a wait context, we need to consume it and mark it as consumed after
365	// If there is no context then we can skip the in progress phase
366	struct oneshot * want = expected == 0p ? 1p : 2p;
367	if(__atomic_compare_exchange_n(&this.ptr, &expected, want, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
368	if( expected == 0p ) { /* paranoid */ verify( this.ptr == 1p); return 0p; }
369	thread$ * ret = post( *expected, do_unpark );
370	__atomic_store_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
371	return ret;
372	}
373	}
374
375	}
376
377	// Wait for the future to be fulfilled
378	bool wait( future_t & this ) {
379	oneshot temp;
380	if( !setup(this, temp) ) return false;
381
382	// Wait context is setup, just wait on it
383	bool ret = wait( temp );
384
385	// Wait for the future to tru
386	while( this.ptr == 2p ) Pause();
387	// Make sure the state makes sense
388	// Should be fulfilled, could be in progress but it's out of date if so
389	// since if that is the case, the oneshot was fulfilled (unparking this thread)
390	// and the oneshot should not be needed any more
391	__attribute__((unused)) struct oneshot * was = this.ptr;
392	/* paranoid */ verifyf( was == 1p, "Expected this.ptr to be 1p, was %p\n", was );
393
394	// Mark the future as fulfilled, to be consistent
395	// with potential calls to avail
396	// this.ptr = 1p;
397	return ret;
398	}
399	}
400
401	//-----------------------------------------------------------------------
402	// Statics call at the end of each thread to register statistics
403	#if !defined(__CFA_NO_STATISTICS__)
404	static inline struct __stats_t * __tls_stats() {
405	/* paranoid */ verify( ! __preemption_enabled() );
406	/* paranoid */ verify( kernelTLS().this_stats );
407	return kernelTLS().this_stats;
408	}
409
410	#define __STATS__(in_kernel, ...) { \
411	if( !(in_kernel) ) disable_interrupts(); \
412	with( *__tls_stats() ) { \
413	__VA_ARGS__ \
414	} \
415	if( !(in_kernel) ) enable_interrupts(); \
416	}
417	#else
418	#define __STATS__(in_kernel, ...)
419	#endif
420	}
421	}
422	#endif

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