source: trunk/kernel/libk/remote_rwlock.c @ 337

Last change on this file since 337 was 337, checked in by alain, 4 years ago

Introduce the delayed context switch if current thread has a lock.

File size: 7.4 KB
Line 
1/*
2 * remote_rwlock.c - kernel remote rwlock implementation.
3 *
4 * Authors    Alain   Greiner (2016,2017)
5 *
6 * Copyright (c) UPMC Sorbonne Universites
7 *
8 * This file is part of ALMOS-MKH.
9 *
10 * ALMOS-MKH is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by
12 * the Free Software Foundation; version 2.0 of the License.
13 *
14 * ALMOS-MKH is distributed in the hope that it will be useful, but
15 * WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with ALMOS-MKH; if not, write to the Free Software Foundation,
21 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24#include <hal_types.h>
25#include <hal_remote.h>
26#include <hal_irqmask.h>
27#include <thread.h>
28#include <printk.h>
29#include <cluster.h>
30#include <scheduler.h>
31#include <remote_rwlock.h>
32
33///////////////////////////////////////////
34void remote_rwlock_init( xptr_t lock_xp )
35{ 
36    remote_rwlock_t * lock_ptr = (remote_rwlock_t *)GET_PTR( lock_xp );
37    cxy_t             lock_cxy = GET_CXY( lock_xp );
38
39    hal_remote_sw ( XPTR( lock_cxy , &lock_ptr->ticket )  , 0 );
40    hal_remote_sw ( XPTR( lock_cxy , &lock_ptr->current ) , 0 );
41    hal_remote_sw ( XPTR( lock_cxy , &lock_ptr->count )   , 0 );
42    hal_remote_swd( XPTR( lock_cxy , &lock_ptr->owner )   , XPTR_NULL );
43}
44
45//////////////////////////////////////////////
46void remote_rwlock_rd_lock( xptr_t lock_xp )
47{ 
48        reg_t      mode;
49    uint32_t   ticket;
50
51    // get cluster and local pointer on remote_rwlock
52    remote_rwlock_t * lock_ptr = (remote_rwlock_t *)GET_PTR( lock_xp );
53    cxy_t             lock_cxy = GET_CXY( lock_xp );
54
55    // get cluster and local pointer on local thread
56    thread_t          * thread_ptr = CURRENT_THREAD;
57
58    // extended pointers on ticket, current, count
59    xptr_t              ticket_xp  = XPTR( lock_cxy   , &lock_ptr->ticket );
60    xptr_t              current_xp = XPTR( lock_cxy   , &lock_ptr->current );
61    xptr_t              count_xp   = XPTR( lock_cxy   , &lock_ptr->count );
62
63    // disable interrupts
64    hal_disable_irq( &mode );
65
66    // get next free ticket
67    ticket = hal_remote_atomic_add( ticket_xp , 1 );
68
69    // busy waiting loop to take the lock
70        while( ticket != hal_remote_lw( current_xp ) )
71        {
72        hal_fixed_delay( CONFIG_RWLOCK_DELAY );
73        }
74
75    ////////// From here we have the lock  ////////////
76
77    // increment count
78    hal_remote_atomic_add( count_xp , 1 );
79
80    // increment thread.remote_locks
81    thread_ptr->remote_locks++;
82
83    // sync
84    hal_fence();
85
86    // release lock to allow several simultaneous readers
87    hal_remote_atomic_add( current_xp , 1 );
88
89    // enable interrupts
90        hal_restore_irq( mode );
91
92}  // end remote_rwlock_rd_lock()
93
94////////////////////////////////////////////////
95void remote_rwlock_rd_unlock( xptr_t lock_xp )
96{
97        reg_t               mode;
98
99    // get cluster and local pointer on remote_rwlock
100    remote_rwlock_t * lock_ptr = (remote_rwlock_t *)GET_PTR( lock_xp );
101    cxy_t             lock_cxy = GET_CXY( lock_xp );
102
103    // get cluster and local pointer on local thread
104    thread_t          * thread_ptr = CURRENT_THREAD;
105
106    // extended pointers on lock->count
107    xptr_t              count_xp = XPTR( lock_cxy   , &lock_ptr->count );
108
109    // disable interrupts
110        hal_disable_irq( &mode );
111 
112    // decrement count
113    hal_remote_atomic_add( count_xp , -1 );
114
115    // decrement thread.remote_locks
116        thread_ptr->remote_locks--;
117
118    // enable interrupts
119        hal_restore_irq( mode );
120   
121    // deschedule if pending request
122    thread_check_sched();
123
124}  // end remote_rwlock_rd_unlock()
125
126//////////////////////////////////////////////
127void remote_rwlock_wr_lock( xptr_t lock_xp )
128{ 
129        reg_t      mode;
130    uint32_t   ticket;
131
132    // get cluster and local pointer on remote_rwlock
133    remote_rwlock_t * lock_ptr = (remote_rwlock_t *)GET_PTR( lock_xp );
134    cxy_t             lock_cxy = GET_CXY( lock_xp );
135
136    // get cluster and local pointer on local thread
137    cxy_t               thread_cxy = local_cxy;
138    thread_t          * thread_ptr = CURRENT_THREAD;
139
140    // compute extended pointers on lock->ticket, lock->owner
141    xptr_t              ticket_xp  = XPTR( lock_cxy   , &lock_ptr->ticket );
142    xptr_t              count_xp   = XPTR( lock_cxy   , &lock_ptr->count );
143    xptr_t              current_xp = XPTR( lock_cxy   , &lock_ptr->current );
144    xptr_t              owner_xp   = XPTR( lock_cxy   , &lock_ptr->owner );
145    xptr_t              thread_xp  = XPTR( thread_cxy , thread_ptr );
146
147    // disable interrupts
148    hal_disable_irq( &mode );
149
150    // get next free ticket
151    ticket = hal_remote_atomic_add( ticket_xp , 1 );
152
153    // loop to take the lock
154        while( ticket != hal_remote_lw( current_xp ) )
155        {
156        hal_fixed_delay( CONFIG_RWLOCK_DELAY );
157        }
158
159    ////////// From here we have the lock  ////////////
160
161    // wait completion of read accesses
162    while( hal_remote_lw( count_xp ) != 0 )
163    {
164        hal_fixed_delay( CONFIG_RWLOCK_DELAY );
165    }
166
167    // register owner thread
168    hal_remote_swd( owner_xp , thread_xp );
169
170    // increment thread.remote_locks
171    thread_ptr->remote_locks++;
172
173    // enable interrupts
174        hal_restore_irq( mode );
175
176}  // end remote_rwlock_wr_lock()
177
178//////////////////////////////////////////////
179void remote_rwlock_wr_unlock( xptr_t lock_xp )
180{
181        reg_t               mode;
182
183    // get cluster and local pointer on remote_rwlock
184    remote_rwlock_t * lock_ptr = (remote_rwlock_t *)GET_PTR( lock_xp );
185    cxy_t             lock_cxy = GET_CXY( lock_xp );
186
187    // get cluster and local pointer on local thread
188    thread_t          * thread_ptr = CURRENT_THREAD;
189
190    // compute extended pointers on lock->ticket, lock->owner
191    xptr_t              current_xp = XPTR( lock_cxy   , &lock_ptr->current );
192    xptr_t              owner_xp   = XPTR( lock_cxy   , &lock_ptr->owner );
193
194    // disable interrupts
195        hal_disable_irq( &mode );
196 
197    // unregister owner thread, and release lock
198    hal_remote_swd( owner_xp , XPTR_NULL );
199    hal_remote_atomic_add( current_xp , 1 );
200
201    // decrement thread.remote_locks
202        thread_ptr->remote_locks--;
203
204    // enable interrupts
205        hal_restore_irq( mode );
206   
207    // deschedule if pending request
208    thread_check_sched();
209
210}  // end remote_rwlock_wr_unlock()
211
212///////////////////////////////////////////
213void remote_rwlock_print( xptr_t   lock_xp,
214                          char   * comment )
215{
216    uint32_t     ticket;                // first free ticket index
217    uint32_t     current;               // ticket index of current owner
218    uint32_t     count;                 // current number of reader threads
219    xptr_t       owner;                 // extended pointer on writer thread
220
221    // get cluster and local pointer on remote_rwlock
222    remote_rwlock_t * lock_ptr = (remote_rwlock_t *)GET_PTR( lock_xp );
223    cxy_t             lock_cxy = GET_CXY( lock_xp );
224
225    ticket  = hal_remote_lw ( XPTR( lock_cxy , &lock_ptr->ticket ) );
226    current = hal_remote_lw ( XPTR( lock_cxy , &lock_ptr->current ) );
227    count   = hal_remote_lw ( XPTR( lock_cxy , &lock_ptr->count ) );
228    owner   = hal_remote_lwd( XPTR( lock_cxy , &lock_ptr->owner ) );
229
230    printk("\n*** rwlock <%l> %s : ticket = %d / current = %d / count = %d / owner = %l\n",
231           lock_xp , comment , ticket , current , count , owner ); 
232
233}  // end remote_rwlock_print()
234
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