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locks.hfa @ 0b84b15

ADTarm-ehast-experimentalenumforall-pointer-decayjacob/cs343-translationnew-ast-unique-exprpthread-emulationqualifiedEnum

Last change on this file since 0b84b15 was e235429, checked in by Thierry Delisle <tdelisle@…>, 4 years ago
Removed last parker/unparker information is it was not particularly useful
Property mode set to `100644`
File size: 11.9 KB

Line
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	// bits/locks.hfa -- Fast internal locks.
8	//
9	// Author : Thierry Delisle
10	// Created On : Tue Oct 31 15:14:38 2017
11	// Last Modified By : Peter A. Buhr
12	// Last Modified On : Wed Aug 12 14:18:07 2020
13	// Update Count : 13
14	//
15
16	#pragma once
17
18	#include "bits/debug.hfa"
19	#include "bits/defs.hfa"
20	#include <assert.h>
21
22	#ifdef __cforall
23	extern "C" {
24	#include <pthread.h>
25	}
26	#endif
27
28	// pause to prevent excess processor bus usage
29	#if defined( __i386 ) \|\| defined( __x86_64 )
30	#define Pause() __asm__ __volatile__ ( "pause" : : : )
31	#elif defined( __ARM_ARCH )
32	#define Pause() __asm__ __volatile__ ( "YIELD" : : : )
33	#else
34	#error unsupported architecture
35	#endif
36
37	struct __spinlock_t {
38	// Wrap in struct to prevent false sharing with debug info
39	volatile bool lock;
40	#ifdef __CFA_DEBUG__
41	// previous function to acquire the lock
42	const char * prev_name;
43	// previous thread to acquire the lock
44	void* prev_thrd;
45	#endif
46	};
47
48	#ifdef __cforall
49	extern "C" {
50	extern void disable_interrupts() OPTIONAL_THREAD;
51	extern void enable_interrupts_noPoll() OPTIONAL_THREAD;
52
53	#ifdef __CFA_DEBUG__
54	void __cfaabi_dbg_record_lock(__spinlock_t & this, const char prev_name[]);
55	#else
56	#define __cfaabi_dbg_record_lock(x, y)
57	#endif
58	}
59
60	static inline void ?{}( __spinlock_t & this ) {
61	this.lock = 0;
62	}
63
64	// Lock the spinlock, return false if already acquired
65	static inline bool try_lock ( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) {
66	disable_interrupts();
67	bool result = (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0);
68	if( result ) {
69	__cfaabi_dbg_record_lock( this, caller );
70	} else {
71	enable_interrupts_noPoll();
72	}
73	return result;
74	}
75
76	// Lock the spinlock, spin if already acquired
77	static inline void lock( __spinlock_t & this __cfaabi_dbg_ctx_param2 ) {
78	#ifndef NOEXPBACK
79	enum { SPIN_START = 4, SPIN_END = 64 * 1024, };
80	unsigned int spin = SPIN_START;
81	#endif
82
83	disable_interrupts();
84	for ( unsigned int i = 1;; i += 1 ) {
85	if ( (this.lock == 0) && (__atomic_test_and_set( &this.lock, __ATOMIC_ACQUIRE ) == 0) ) break;
86	#ifndef NOEXPBACK
87	// exponential spin
88	for ( volatile unsigned int s = 0; s < spin; s += 1 ) Pause();
89
90	// slowly increase by powers of 2
91	if ( i % 64 == 0 ) spin += spin;
92
93	// prevent overflow
94	if ( spin > SPIN_END ) spin = SPIN_START;
95	#else
96	Pause();
97	#endif
98	}
99	__cfaabi_dbg_record_lock( this, caller );
100	}
101
102	static inline void unlock( __spinlock_t & this ) {
103	__atomic_clear( &this.lock, __ATOMIC_RELEASE );
104	enable_interrupts_noPoll();
105	}
106
107
108	#ifdef __CFA_WITH_VERIFY__
109	extern bool __cfaabi_dbg_in_kernel();
110	#endif
111
112	extern "C" {
113	char * strerror(int);
114	}
115	#define CHECKED(x) { int err = x; if( err != 0 ) abort("KERNEL ERROR: Operation \"" #x "\" return error %d - %s\n", err, strerror(err)); }
116
117	struct __bin_sem_t {
118	pthread_mutex_t lock;
119	pthread_cond_t cond;
120	int val;
121	};
122
123	static inline void ?{}(__bin_sem_t & this) with( this ) {
124	// Create the mutex with error checking
125	pthread_mutexattr_t mattr;
126	pthread_mutexattr_init( &mattr );
127	pthread_mutexattr_settype( &mattr, PTHREAD_MUTEX_ERRORCHECK_NP);
128	pthread_mutex_init(&lock, &mattr);
129
130	pthread_cond_init (&cond, (const pthread_condattr_t *)0p); // workaround trac#208: cast should not be required
131	val = 0;
132	}
133
134	static inline void ^?{}(__bin_sem_t & this) with( this ) {
135	CHECKED( pthread_mutex_destroy(&lock) );
136	CHECKED( pthread_cond_destroy (&cond) );
137	}
138
139	static inline void wait(__bin_sem_t & this) with( this ) {
140	verify(__cfaabi_dbg_in_kernel());
141	CHECKED( pthread_mutex_lock(&lock) );
142	while(val < 1) {
143	pthread_cond_wait(&cond, &lock);
144	}
145	val -= 1;
146	CHECKED( pthread_mutex_unlock(&lock) );
147	}
148
149	static inline bool post(__bin_sem_t & this) with( this ) {
150	bool needs_signal = false;
151
152	CHECKED( pthread_mutex_lock(&lock) );
153	if(val < 1) {
154	val += 1;
155	pthread_cond_signal(&cond);
156	needs_signal = true;
157	}
158	CHECKED( pthread_mutex_unlock(&lock) );
159
160	return needs_signal;
161	}
162
163	#undef CHECKED
164
165	struct $thread;
166	extern void park( void );
167	extern void unpark( struct $thread * this );
168	static inline struct $thread * active_thread ();
169
170	// Semaphore which only supports a single thread
171	struct single_sem {
172	struct $thread * volatile ptr;
173	};
174
175	static inline {
176	void ?{}(single_sem & this) {
177	this.ptr = 0p;
178	}
179
180	void ^?{}(single_sem & this) {}
181
182	bool wait(single_sem & this) {
183	for() {
184	struct $thread * expected = this.ptr;
185	if(expected == 1p) {
186	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
187	return false;
188	}
189	}
190	else {
191	/* paranoid */ verify( expected == 0p );
192	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
193	park();
194	return true;
195	}
196	}
197
198	}
199	}
200
201	bool post(single_sem & this) {
202	for() {
203	struct $thread * expected = this.ptr;
204	if(expected == 1p) return false;
205	if(expected == 0p) {
206	if(__atomic_compare_exchange_n(&this.ptr, &expected, 1p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
207	return false;
208	}
209	}
210	else {
211	if(__atomic_compare_exchange_n(&this.ptr, &expected, 0p, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
212	unpark( expected );
213	return true;
214	}
215	}
216	}
217	}
218	}
219
220	// Synchronozation primitive which only supports a single thread and one post
221	// Similar to a binary semaphore with a 'one shot' semantic
222	// is expected to be discarded after each party call their side
223	struct oneshot {
224	// Internal state :
225	// 0p : is initial state (wait will block)
226	// 1p : fulfilled (wait won't block)
227	// any thread : a thread is currently waiting
228	struct $thread * volatile ptr;
229	};
230
231	static inline {
232	void ?{}(oneshot & this) {
233	this.ptr = 0p;
234	}
235
236	void ^?{}(oneshot & this) {}
237
238	// Wait for the post, return immidiately if it already happened.
239	// return true if the thread was parked
240	bool wait(oneshot & this) {
241	for() {
242	struct $thread * expected = this.ptr;
243	if(expected == 1p) return false;
244	/* paranoid */ verify( expected == 0p );
245	if(__atomic_compare_exchange_n(&this.ptr, &expected, active_thread(), false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
246	park();
247	/* paranoid */ verify( this.ptr == 1p );
248	return true;
249	}
250	}
251	}
252
253	// Mark as fulfilled, wake thread if needed
254	// return true if a thread was unparked
255	bool post(oneshot & this) {
256	struct $thread * got = __atomic_exchange_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
257	if( got == 0p ) return false;
258	unpark( got );
259	return true;
260	}
261	}
262
263	// base types for future to build upon
264	// It is based on the 'oneshot' type to allow multiple futures
265	// to block on the same instance, permitting users to block a single
266	// thread on "any of" [a given set of] futures.
267	// does not support multiple threads waiting on the same future
268	struct future_t {
269	// Internal state :
270	// 0p : is initial state (wait will block)
271	// 1p : fulfilled (wait won't block)
272	// 2p : in progress ()
273	// 3p : abandoned, server should delete
274	// any oneshot : a context has been setup to wait, a thread could wait on it
275	struct oneshot * volatile ptr;
276	};
277
278	static inline {
279	void ?{}(future_t & this) {
280	this.ptr = 0p;
281	}
282
283	void ^?{}(future_t & this) {}
284
285	// check if the future is available
286	bool available( future_t & this ) {
287	return this.ptr == 1p;
288	}
289
290	// Prepare the future to be waited on
291	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
292	bool setup( future_t & this, oneshot & wait_ctx ) {
293	/* paranoid */ verify( wait_ctx.ptr == 0p );
294	// The future needs to set the wait context
295	for() {
296	struct oneshot * expected = this.ptr;
297	// Is the future already fulfilled?
298	if(expected == 1p) return false; // Yes, just return false (didn't block)
299
300	// The future is not fulfilled, try to setup the wait context
301	/* paranoid */ verify( expected == 0p );
302	if(__atomic_compare_exchange_n(&this.ptr, &expected, &wait_ctx, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
303	return true;
304	}
305	}
306	}
307
308	// Stop waiting on a future
309	// When multiple futures are waited for together in "any of" pattern
310	// futures that weren't fulfilled before the thread woke up
311	// should retract the wait ctx
312	// intented to be use by wait, wait_any, waitfor, etc. rather than used directly
313	void retract( future_t & this, oneshot & wait_ctx ) {
314	// Remove the wait context
315	struct oneshot * got = __atomic_exchange_n( &this.ptr, 0p, __ATOMIC_SEQ_CST);
316
317	// got == 0p: future was never actually setup, just return
318	if( got == 0p ) return;
319
320	// got == wait_ctx: since fulfil does an atomic_swap,
321	// if we got back the original then no one else saw context
322	// It is safe to delete (which could happen after the return)
323	if( got == &wait_ctx ) return;
324
325	// got == 1p: the future is ready and the context was fully consumed
326	// the server won't use the pointer again
327	// It is safe to delete (which could happen after the return)
328	if( got == 1p ) return;
329
330	// got == 2p: the future is ready but the context hasn't fully been consumed
331	// spin until it is safe to move on
332	if( got == 2p ) {
333	while( this.ptr != 1p ) Pause();
334	return;
335	}
336
337	// got == any thing else, something wen't wrong here, abort
338	abort("Future in unexpected state");
339	}
340
341	// Mark the future as abandoned, meaning it will be deleted by the server
342	void abandon( future_t & this ) {
343	struct oneshot * got = __atomic_exchange_n( &this.ptr, 3p, __ATOMIC_SEQ_CST);
344
345	// got == 2p: the future is ready but the context hasn't fully been consumed
346	// spin until it is safe to move on
347	if( got == 2p ) {
348	while( this.ptr != 1p ) Pause();
349	}
350	return;
351	}
352
353	// from the server side, mark the future as fulfilled
354	// delete it if needed
355	bool fulfil( future_t & this ) {
356	for() {
357	struct oneshot * expected = this.ptr;
358	// was this abandoned?
359	#if defined(__GNUC__) && __GNUC__ >= 7
360	#pragma GCC diagnostic push
361	#pragma GCC diagnostic ignored "-Wfree-nonheap-object"
362	#endif
363	if( expected == 3p ) { free( &this ); return false; }
364	#if defined(__GNUC__) && __GNUC__ >= 7
365	#pragma GCC diagnostic pop
366	#endif
367
368	/* paranoid */ verify( expected != 1p ); // Future is already fulfilled, should not happen
369	/* paranoid */ verify( expected != 2p ); // Future is bein fulfilled by someone else, this is even less supported then the previous case.
370
371	// If there is a wait context, we need to consume it and mark it as consumed after
372	// If there is no context then we can skip the in progress phase
373	struct oneshot * want = expected == 0p ? 1p : 2p;
374	if(__atomic_compare_exchange_n(&this.ptr, &expected, want, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
375	if( expected == 0p ) { /* paranoid */ verify( this.ptr == 1p); return false; }
376	bool ret = post( *expected );
377	__atomic_store_n( &this.ptr, 1p, __ATOMIC_SEQ_CST);
378	return ret;
379	}
380	}
381
382	}
383
384	// Wait for the future to be fulfilled
385	bool wait( future_t & this ) {
386	oneshot temp;
387	if( !setup(this, temp) ) return false;
388
389	// Wait context is setup, just wait on it
390	bool ret = wait( temp );
391
392	// Wait for the future to tru
393	while( this.ptr == 2p ) Pause();
394	// Make sure the state makes sense
395	// Should be fulfilled, could be in progress but it's out of date if so
396	// since if that is the case, the oneshot was fulfilled (unparking this thread)
397	// and the oneshot should not be needed any more
398	__attribute__((unused)) struct oneshot * was = this.ptr;
399	/* paranoid */ verifyf( was == 1p, "Expected this.ptr to be 1p, was %p\n", was );
400
401	// Mark the future as fulfilled, to be consistent
402	// with potential calls to avail
403	// this.ptr = 1p;
404	return ret;
405	}
406	}
407	#endif

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