source: libcfa/src/concurrency/locks.hfa

Last change on this file was bbe3719, checked in by caparsons <caparson@…>, 6 weeks ago

cleaned up some mutex stmt related code

  • Property mode set to 100644
File size: 12.7 KB
Line 
1//
2// Cforall Version 1.0.0 Copyright (C) 2021 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// locks.hfa -- PUBLIC
8// Runtime locks that used with the runtime thread system.
9//
10// Author           : Colby Alexander Parsons
11// Created On       : Thu Jan 21 19:46:50 2021
12// Last Modified By :
13// Last Modified On :
14// Update Count     :
15//
16
17#pragma once
18
19#include <stdbool.h>
20#include <stdio.h>
21
22#include "bits/weakso_locks.hfa"
23#include "containers/queueLockFree.hfa"
24#include "containers/list.hfa"
25
26#include "limits.hfa"
27#include "thread.hfa"
28
29#include "time_t.hfa"
30#include "time.hfa"
31
32//-----------------------------------------------------------------------------
33// Semaphores
34
35// '0-nary' semaphore
36// Similar to a counting semaphore except the value of one is never reached
37// as a consequence, a V() that would bring the value to 1 *spins* until
38// a P consumes it
39struct Semaphore0nary {
40        __spinlock_t lock; // needed to protect
41        mpsc_queue(thread$) queue;
42};
43
44static inline bool P(Semaphore0nary & this, thread$ * thrd) {
45        /* paranoid */ verify(!thrd`next);
46        /* paranoid */ verify(!(&(*thrd)`next));
47
48        push(this.queue, thrd);
49        return true;
50}
51
52static inline bool P(Semaphore0nary & this) {
53    thread$ * thrd = active_thread();
54    P(this, thrd);
55    park();
56    return true;
57}
58
59static inline thread$ * V(Semaphore0nary & this, bool doUnpark = true) {
60        thread$ * next;
61        lock(this.lock __cfaabi_dbg_ctx2);
62                for (;;) {
63                        next = pop(this.queue);
64                        if (next) break;
65                        Pause();
66                }
67        unlock(this.lock);
68
69        if (doUnpark) unpark(next);
70        return next;
71}
72
73// Wrapper used on top of any sempahore to avoid potential locking
74struct BinaryBenaphore {
75        volatile ssize_t counter;
76};
77
78static inline {
79        void ?{}(BinaryBenaphore & this) { this.counter = 0; }
80        void ?{}(BinaryBenaphore & this, zero_t) { this.counter = 0; }
81        void ?{}(BinaryBenaphore & this, one_t ) { this.counter = 1; }
82
83        // returns true if no blocking needed
84        bool P(BinaryBenaphore & this) {
85                return __atomic_fetch_sub(&this.counter, 1, __ATOMIC_SEQ_CST) > 0;
86        }
87
88        bool tryP(BinaryBenaphore & this) {
89                ssize_t c = this.counter;
90                /* paranoid */ verify( c > MIN );
91                return (c >= 1) && __atomic_compare_exchange_n(&this.counter, &c, c-1, false, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);
92        }
93
94        // returns true if notify needed
95        bool V(BinaryBenaphore & this) {
96                ssize_t c = 0;
97                for () {
98                        /* paranoid */ verify( this.counter < MAX );
99                        if (__atomic_compare_exchange_n(&this.counter, &c, c+1, false, __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST)) {
100                                if (c == 0) return true;
101                                /* paranoid */ verify(c < 0);
102                                return false;
103                        } else {
104                                if (c == 1) return true;
105                                /* paranoid */ verify(c < 1);
106                                Pause();
107                        }
108                }
109        }
110}
111
112// Binary Semaphore based on the BinaryBenaphore on top of the 0-nary Semaphore
113struct ThreadBenaphore {
114        BinaryBenaphore ben;
115        Semaphore0nary  sem;
116};
117
118static inline void ?{}(ThreadBenaphore & this) {}
119static inline void ?{}(ThreadBenaphore & this, zero_t) { (this.ben){ 0 }; }
120static inline void ?{}(ThreadBenaphore & this, one_t ) { (this.ben){ 1 }; }
121
122static inline bool P(ThreadBenaphore & this)              { return P(this.ben) ? false : P(this.sem); }
123static inline bool tryP(ThreadBenaphore & this)           { return tryP(this.ben); }
124static inline bool P(ThreadBenaphore & this, bool wait)   { return wait ? P(this) : tryP(this); }
125
126static inline thread$ * V(ThreadBenaphore & this, bool doUnpark = true) {
127        if (V(this.ben)) return 0p;
128        return V(this.sem, doUnpark);
129}
130
131//-----------------------------------------------------------------------------
132// Semaphore
133struct semaphore {
134        __spinlock_t lock;
135        int count;
136        __queue_t(thread$) waiting;
137};
138
139void  ?{}(semaphore & this, int count = 1);
140void ^?{}(semaphore & this);
141bool   P (semaphore & this);
142bool   V (semaphore & this);
143bool   V (semaphore & this, unsigned count);
144thread$ * V (semaphore & this, bool );
145
146//----------
147struct single_acquisition_lock {
148        inline blocking_lock;
149};
150
151static inline void  ?{}( single_acquisition_lock & this ) {((blocking_lock &)this){ false, false };}
152static inline void ^?{}( single_acquisition_lock & this ) {}
153static inline void   lock     ( single_acquisition_lock & this ) { lock    ( (blocking_lock &)this ); }
154static inline bool   try_lock ( single_acquisition_lock & this ) { return try_lock( (blocking_lock &)this ); }
155static inline void   unlock   ( single_acquisition_lock & this ) { unlock  ( (blocking_lock &)this ); }
156static inline size_t on_wait  ( single_acquisition_lock & this ) { return on_wait ( (blocking_lock &)this ); }
157static inline void   on_wakeup( single_acquisition_lock & this, size_t v ) { on_wakeup ( (blocking_lock &)this, v ); }
158static inline void   on_notify( single_acquisition_lock & this, struct thread$ * t ) { on_notify( (blocking_lock &)this, t ); }
159
160//----------
161struct owner_lock {
162        inline blocking_lock;
163};
164
165static inline void  ?{}( owner_lock & this ) {((blocking_lock &)this){ true, true };}
166static inline void ^?{}( owner_lock & this ) {}
167static inline void   lock     ( owner_lock & this ) { lock    ( (blocking_lock &)this ); }
168static inline bool   try_lock ( owner_lock & this ) { return try_lock( (blocking_lock &)this ); }
169static inline void   unlock   ( owner_lock & this ) { unlock  ( (blocking_lock &)this ); }
170static inline size_t on_wait  ( owner_lock & this ) { return on_wait ( (blocking_lock &)this ); }
171static inline void   on_wakeup( owner_lock & this, size_t v ) { on_wakeup ( (blocking_lock &)this, v ); }
172static inline void   on_notify( owner_lock & this, struct thread$ * t ) { on_notify( (blocking_lock &)this, t ); }
173
174struct fast_lock {
175        thread$ * volatile owner;
176        ThreadBenaphore sem;
177};
178
179static inline void ?{}(fast_lock & this) { this.owner = 0p; }
180
181static inline bool $try_lock(fast_lock & this, thread$ * thrd) {
182    thread$ * exp = 0p;
183    return __atomic_compare_exchange_n(&this.owner, &exp, thrd, false, __ATOMIC_SEQ_CST, __ATOMIC_RELAXED);
184}
185
186static inline void lock( fast_lock & this ) __attribute__((artificial));
187static inline void lock( fast_lock & this ) {
188        thread$ * thrd = active_thread();
189        /* paranoid */verify(thrd != this.owner);
190
191        for (;;) {
192                if ($try_lock(this, thrd)) return;
193                P(this.sem);
194        }
195}
196
197static inline bool try_lock( fast_lock & this ) __attribute__((artificial));
198static inline bool try_lock ( fast_lock & this ) {
199        thread$ * thrd = active_thread();
200        /* paranoid */ verify(thrd != this.owner);
201        return $try_lock(this, thrd);
202}
203
204static inline thread$ * unlock( fast_lock & this ) __attribute__((artificial));
205static inline thread$ * unlock( fast_lock & this ) {
206        /* paranoid */ verify(active_thread() == this.owner);
207
208        // open 'owner' before unlocking anyone
209        // so new and unlocked threads don't park incorrectly.
210        // This may require additional fencing on ARM.
211        this.owner = 0p;
212
213        return V(this.sem);
214}
215
216static inline size_t on_wait( fast_lock & this ) { unlock(this); return 0; }
217static inline void on_wakeup( fast_lock & this, size_t ) { lock(this); }
218static inline void on_notify( fast_lock &, struct thread$ * t ) { unpark(t); }
219
220struct mcs_node {
221        mcs_node * volatile next;
222        single_sem sem;
223};
224
225static inline void ?{}(mcs_node & this) { this.next = 0p; }
226
227static inline mcs_node * volatile & ?`next ( mcs_node * node ) {
228        return node->next;
229}
230
231struct mcs_lock {
232        mcs_queue(mcs_node) queue;
233};
234
235static inline void lock(mcs_lock & l, mcs_node & n) {
236        if(push(l.queue, &n))
237                wait(n.sem);
238}
239
240static inline void unlock(mcs_lock & l, mcs_node & n) {
241        mcs_node * next = advance(l.queue, &n);
242        if(next) post(next->sem);
243}
244
245struct linear_backoff_then_block_lock {
246        // Spin lock used for mutual exclusion
247        __spinlock_t spinlock;
248
249        // Current thread owning the lock
250        struct thread$ * owner;
251
252        // List of blocked threads
253        dlist( thread$ ) blocked_threads;
254
255        // Used for comparing and exchanging
256        volatile size_t lock_value;
257
258        // used for linear backoff spinning
259        int spin_start;
260        int spin_end;
261        int spin_count;
262
263        // after unsuccessful linear backoff yield this many times
264        int yield_count;
265};
266
267static inline void  ?{}( linear_backoff_then_block_lock & this, int spin_start, int spin_end, int spin_count, int yield_count ) {
268        this.spinlock{};
269        this.blocked_threads{};
270        this.lock_value = 0;
271        this.spin_start = spin_start;
272        this.spin_end = spin_end;
273        this.spin_count = spin_count;
274        this.yield_count = yield_count;
275}
276static inline void  ?{}( linear_backoff_then_block_lock & this ) { this{4, 1024, 16, 0}; }
277static inline void ^?{}( linear_backoff_then_block_lock & this ) {}
278static inline void ?{}( linear_backoff_then_block_lock & this, linear_backoff_then_block_lock this2 ) = void;
279static inline void ?=?( linear_backoff_then_block_lock & this, linear_backoff_then_block_lock this2 ) = void;
280
281static inline bool internal_try_lock(linear_backoff_then_block_lock & this, size_t & compare_val) with(this) {
282        if (__atomic_compare_exchange_n(&lock_value, &compare_val, 1, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED)) {
283                owner = active_thread();
284                return true;
285        }
286        return false;
287}
288
289static inline bool try_lock(linear_backoff_then_block_lock & this) { size_t compare_val = 0; return internal_try_lock(this, compare_val); }
290
291static inline bool try_lock_contention(linear_backoff_then_block_lock & this) with(this) {
292        if (__atomic_exchange_n(&lock_value, 2, __ATOMIC_ACQUIRE) == 0) {
293                owner = active_thread();
294                return true;
295        }
296        return false;
297}
298
299static inline bool block(linear_backoff_then_block_lock & this) with(this) {
300        lock( spinlock __cfaabi_dbg_ctx2 );
301        if (lock_value != 2) {
302                unlock( spinlock );
303                return true;
304        }
305        insert_last( blocked_threads, *active_thread() );
306        unlock( spinlock );
307        park( );
308        return true;
309}
310
311static inline bool lock(linear_backoff_then_block_lock & this) with(this) {
312        // if owner just return
313        if (active_thread() == owner) return true;
314        size_t compare_val = 0;
315        int spin = spin_start;
316        // linear backoff
317        for( ;; ) {
318                compare_val = 0;
319                if (internal_try_lock(this, compare_val)) return true;
320                if (2 == compare_val) break;
321                for (int i = 0; i < spin; i++) Pause();
322                if (spin >= spin_end) break;
323                spin += spin;
324        }
325
326        if(2 != compare_val && try_lock_contention(this)) return true;
327        // block until signalled
328        while (block(this)) if(try_lock_contention(this)) return true;
329
330        // this should never be reached as block(this) always returns true
331        return false;
332}
333
334static inline void unlock(linear_backoff_then_block_lock & this) with(this) {
335        verify(lock_value > 0);
336    owner = 0p;
337    if (__atomic_exchange_n(&lock_value, 0, __ATOMIC_RELEASE) == 1) return;
338        lock( spinlock __cfaabi_dbg_ctx2 );
339        thread$ * t = &try_pop_front( blocked_threads );
340        unlock( spinlock );
341        unpark( t );
342}
343
344static inline void on_notify(linear_backoff_then_block_lock & this, struct thread$ * t ) { unpark(t); }
345static inline size_t on_wait(linear_backoff_then_block_lock & this) { unlock(this); return 0; }
346static inline void on_wakeup(linear_backoff_then_block_lock & this, size_t recursion ) { lock(this); }
347
348//-----------------------------------------------------------------------------
349// is_blocking_lock
350trait is_blocking_lock(L & | sized(L)) {
351        // For synchronization locks to use when acquiring
352        void on_notify( L &, struct thread$ * );
353
354        // For synchronization locks to use when releasing
355        size_t on_wait( L & );
356
357        // to set recursion count after getting signalled;
358        void on_wakeup( L &, size_t recursion );
359};
360
361//-----------------------------------------------------------------------------
362// // info_thread
363// // the info thread is a wrapper around a thread used
364// // to store extra data for use in the condition variable
365forall(L & | is_blocking_lock(L)) {
366        struct info_thread;
367
368        // // for use by sequence
369        // info_thread(L) *& Back( info_thread(L) * this );
370        // info_thread(L) *& Next( info_thread(L) * this );
371}
372
373//-----------------------------------------------------------------------------
374// Synchronization Locks
375forall(L & | is_blocking_lock(L)) {
376        struct condition_variable {
377                // Spin lock used for mutual exclusion
378                __spinlock_t lock;
379
380                // List of blocked threads
381                dlist( info_thread(L) ) blocked_threads;
382
383                // Count of current blocked threads
384                int count;
385        };
386
387
388        void  ?{}( condition_variable(L) & this );
389        void ^?{}( condition_variable(L) & this );
390
391        bool notify_one( condition_variable(L) & this );
392        bool notify_all( condition_variable(L) & this );
393
394        uintptr_t front( condition_variable(L) & this );
395
396        bool empty  ( condition_variable(L) & this );
397        int  counter( condition_variable(L) & this );
398
399        void wait( condition_variable(L) & this );
400        void wait( condition_variable(L) & this, uintptr_t info );
401        bool wait( condition_variable(L) & this, Duration duration );
402        bool wait( condition_variable(L) & this, uintptr_t info, Duration duration );
403
404        void wait( condition_variable(L) & this, L & l );
405        void wait( condition_variable(L) & this, L & l, uintptr_t info );
406        bool wait( condition_variable(L) & this, L & l, Duration duration );
407        bool wait( condition_variable(L) & this, L & l, uintptr_t info, Duration duration );
408}
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