source: libcfa/src/concurrency/kernel/fwd.hfa@ 3eaa689

ADT ast-experimental enum forall-pointer-decay pthread-emulation qualifiedEnum
Last change on this file since 3eaa689 was c52f033, checked in by Peter A. Buhr <pabuhr@…>, 4 years ago

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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
26struct thread$;
27struct processor;
28struct cluster;
29
30enum __Preemption_Reason { __NO_PREEMPTION, __ALARM_PREEMPTION, __POLL_PREEMPTION, __MANUAL_PREEMPTION };
31
32#define KERNEL_STORAGE(T,X) __attribute((aligned(__alignof__(T)))) static char storage_##X[sizeof(T)]
33
34#ifdef __cforall
35extern "C" {
36 extern "Cforall" {
37 extern __attribute__((aligned(128))) thread_local struct KernelThreadData {
38 struct thread$ * 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 __xorshift64( kernelTLS().rand_seed );
84 #endif
85 }
86
87 #define M (1_l64u << 48_l64u)
88 #define A (25214903917_l64u)
89 #define AI (18446708753438544741_l64u)
90 #define C (11_l64u)
91 #define D (16_l64u)
92
93 static inline unsigned __tls_rand_fwd() {
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 extern void disable_interrupts();
116 extern void enable_interrupts( bool poll = false );
117
118 extern "Cforall" {
119 enum unpark_hint { UNPARK_LOCAL, UNPARK_REMOTE };
120
121 extern void park( void );
122 extern void unpark( struct thread$ *, unpark_hint );
123 static inline void unpark( struct thread$ * thrd ) { unpark(thrd, UNPARK_LOCAL); }
124 static inline struct thread$ * active_thread () {
125 struct thread$ * t = publicTLS_get( this_thread );
126 /* paranoid */ verify( t );
127 return t;
128 }
129
130 extern bool force_yield( enum __Preemption_Reason );
131
132 static inline void yield() {
133 force_yield(__MANUAL_PREEMPTION);
134 }
135
136 // Yield: yield N times
137 static inline void yield( unsigned times ) {
138 for( times ) {
139 yield();
140 }
141 }
142
143 extern uint64_t thread_rand();
144
145 // Semaphore which only supports a single thread
146 struct single_sem {
147 struct thread$ * volatile ptr;
148 };
149
150 static inline {
151 void ?{}(single_sem & this) {
152 this.ptr = 0p;
153 }
154
155 void ^?{}(single_sem &) {}
156
157 bool wait(single_sem & this) {
158 for() {
159 struct thread$ * expected = this.ptr;
160 if(expected == 1p) {
161 if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
162 return false;
163 }
164 }
165 else {
166 /* paranoid */ verify( expected == 0p );
167 if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
168 park();
169 return true;
170 }
171 }
172
173 }
174 }
175
176 bool post(single_sem & this) {
177 for() {
178 struct thread$ * expected = this.ptr;
179 if(expected == 1p) return false;
180 if(expected == 0p) {
181 if(__atomic_compare_exchange_n(&this.ptr, &expected, 1p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
182 return false;
183 }
184 }
185 else {
186 if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
187 unpark( expected );
188 return true;
189 }
190 }
191 }
192 }
193 }
194
195 // Synchronozation primitive which only supports a single thread and one post
196 // Similar to a binary semaphore with a 'one shot' semantic
197 // is expected to be discarded after each party call their side
198 struct oneshot {
199 // Internal state :
200 // 0p : is initial state (wait will block)
201 // 1p : fulfilled (wait won't block)
202 // any thread : a thread is currently waiting
203 struct thread$ * volatile ptr;
204 };
205
206 static inline {
207 void ?{}(oneshot & this) {
208 this.ptr = 0p;
209 }
210
211 void ^?{}(oneshot &) {}
212
213 // Wait for the post, return immidiately if it already happened.
214 // return true if the thread was parked
215 bool wait(oneshot & this) {
216 for() {
217 struct thread$ * expected = this.ptr;
218 if(expected == 1p) return false;
219 /* paranoid */ verify( expected == 0p );
220 if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
221 park();
222 /* paranoid */ verify( this.ptr == 1p );
223 return true;
224 }
225 }
226 }
227
228 // Mark as fulfilled, wake thread if needed
229 // return true if a thread was unparked
230 thread$ * post(oneshot & this, bool do_unpark = true) {
231 struct thread$ * got = __atomic_exchange_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
232 if( got == 0p ) return 0p;
233 if(do_unpark) unpark( got );
234 return got;
235 }
236 }
237
238 // base types for future to build upon
239 // It is based on the 'oneshot' type to allow multiple futures
240 // to block on the same instance, permitting users to block a single
241 // thread on "any of" [a given set of] futures.
242 // does not support multiple threads waiting on the same future
243 struct future_t {
244 // Internal state :
245 // 0p : is initial state (wait will block)
246 // 1p : fulfilled (wait won't block)
247 // 2p : in progress ()
248 // 3p : abandoned, server should delete
249 // any oneshot : a context has been setup to wait, a thread could wait on it
250 struct oneshot * volatile ptr;
251 };
252
253 static inline {
254 void ?{}(future_t & this) {
255 this.ptr = 0p;
256 }
257
258 void ^?{}(future_t &) {}
259
260 void reset(future_t & this) {
261 // needs to be in 0p or 1p
262 __atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
263 }
264
265 // check if the future is available
266 bool available( future_t & this ) {
267 return this.ptr == 1p;
268 }
269
270 // Prepare the future to be waited on
271 // intented to be use by wait, wait_any, waitfor, etc. rather than used directly
272 bool setup( future_t & this, oneshot & wait_ctx ) {
273 /* paranoid */ verify( wait_ctx.ptr == 0p );
274 // The future needs to set the wait context
275 for() {
276 struct oneshot * expected = this.ptr;
277 // Is the future already fulfilled?
278 if(expected == 1p) return false; // Yes, just return false (didn't block)
279
280 // The future is not fulfilled, try to setup the wait context
281 /* paranoid */ verify( expected == 0p );
282 if(__atomic_compare_exchange_n(&this.ptr, &expected, &wait_ctx, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
283 return true;
284 }
285 }
286 }
287
288 // Stop waiting on a future
289 // When multiple futures are waited for together in "any of" pattern
290 // futures that weren't fulfilled before the thread woke up
291 // should retract the wait ctx
292 // intented to be use by wait, wait_any, waitfor, etc. rather than used directly
293 void retract( future_t & this, oneshot & wait_ctx ) {
294 // Remove the wait context
295 struct oneshot * got = __atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
296
297 // got == 0p: future was never actually setup, just return
298 if( got == 0p ) return;
299
300 // got == wait_ctx: since fulfil does an atomic_swap,
301 // if we got back the original then no one else saw context
302 // It is safe to delete (which could happen after the return)
303 if( got == &wait_ctx ) return;
304
305 // got == 1p: the future is ready and the context was fully consumed
306 // the server won't use the pointer again
307 // It is safe to delete (which could happen after the return)
308 if( got == 1p ) return;
309
310 // got == 2p: the future is ready but the context hasn't fully been consumed
311 // spin until it is safe to move on
312 if( got == 2p ) {
313 while( this.ptr != 1p ) Pause();
314 return;
315 }
316
317 // got == any thing else, something wen't wrong here, abort
318 abort("Future in unexpected state");
319 }
320
321 // Mark the future as abandoned, meaning it will be deleted by the server
322 bool abandon( future_t & this ) {
323 /* paranoid */ verify( this.ptr != 3p );
324
325 // Mark the future as abandonned
326 struct oneshot * got = __atomic_exchange_n( &this.ptr, 3p, __ATOMIC_SEQ_CST);
327
328 // If the future isn't already fulfilled, let the server delete it
329 if( got == 0p ) return false;
330
331 // got == 2p: the future is ready but the context hasn't fully been consumed
332 // spin until it is safe to move on
333 if( got == 2p ) {
334 while( this.ptr != 1p ) Pause();
335 got = 1p;
336 }
337
338 // The future is completed delete it now
339 /* paranoid */ verify( this.ptr != 1p );
340 free( &this );
341 return true;
342 }
343
344 // from the server side, mark the future as fulfilled
345 // delete it if needed
346 thread$ * fulfil( future_t & this, bool do_unpark = true ) {
347 for() {
348 struct oneshot * expected = this.ptr;
349 // was this abandoned?
350 #if defined(__GNUC__) && __GNUC__ >= 7
351 #pragma GCC diagnostic push
352 #pragma GCC diagnostic ignored "-Wfree-nonheap-object"
353 #endif
354 if( expected == 3p ) { free( &this ); return 0p; }
355 #if defined(__GNUC__) && __GNUC__ >= 7
356 #pragma GCC diagnostic pop
357 #endif
358
359 /* paranoid */ verify( expected != 1p ); // Future is already fulfilled, should not happen
360 /* paranoid */ verify( expected != 2p ); // Future is bein fulfilled by someone else, this is even less supported then the previous case.
361
362 // If there is a wait context, we need to consume it and mark it as consumed after
363 // If there is no context then we can skip the in progress phase
364 struct oneshot * want = expected == 0p ? 1p : 2p;
365 if(__atomic_compare_exchange_n(&this.ptr, &expected, want, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
366 if( expected == 0p ) { /* paranoid */ verify( this.ptr == 1p); return 0p; }
367 thread$ * ret = post( *expected, do_unpark );
368 __atomic_store_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
369 return ret;
370 }
371 }
372
373 }
374
375 // Wait for the future to be fulfilled
376 bool wait( future_t & this ) {
377 oneshot temp;
378 if( !setup(this, temp) ) return false;
379
380 // Wait context is setup, just wait on it
381 bool ret = wait( temp );
382
383 // Wait for the future to tru
384 while( this.ptr == 2p ) Pause();
385 // Make sure the state makes sense
386 // Should be fulfilled, could be in progress but it's out of date if so
387 // since if that is the case, the oneshot was fulfilled (unparking this thread)
388 // and the oneshot should not be needed any more
389 __attribute__((unused)) struct oneshot * was = this.ptr;
390 /* paranoid */ verifyf( was == 1p, "Expected this.ptr to be 1p, was %p\n", was );
391
392 // Mark the future as fulfilled, to be consistent
393 // with potential calls to avail
394 // this.ptr = 1p;
395 return ret;
396 }
397 }
398
399 //-----------------------------------------------------------------------
400 // Statics call at the end of each thread to register statistics
401 #if !defined(__CFA_NO_STATISTICS__)
402 static inline struct __stats_t * __tls_stats() {
403 /* paranoid */ verify( ! __preemption_enabled() );
404 /* paranoid */ verify( kernelTLS().this_stats );
405 return kernelTLS().this_stats;
406 }
407
408 #define __STATS__(in_kernel, ...) { \
409 if( !(in_kernel) ) disable_interrupts(); \
410 with( *__tls_stats() ) { \
411 __VA_ARGS__ \
412 } \
413 if( !(in_kernel) ) enable_interrupts(); \
414 }
415 #else
416 #define __STATS__(in_kernel, ...)
417 #endif
418 }
419}
420#endif
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