source: trunk/kernel/libk/rwlock.c @ 603

Last change on this file since 603 was 603, checked in by alain, 3 years ago

Improve the FAT32 file system to support cat, rm, cp commands.

File size: 9.4 KB
Line 
1/*
2 * rwlock.c - kernel local read/write lock implementation.
3 *
4 * Author  Alain Greiner     (2016,2017,2018)
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 <kernel_config.h>
25#include <hal_kernel_types.h>
26#include <hal_atomic.h>
27#include <hal_special.h>
28#include <hal_irqmask.h>
29#include <thread.h>
30#include <printk.h>
31#include <rwlock.h>
32
33//////////////////////////////////////////////////////////////////////////////
34//                Extern global variables
35//////////////////////////////////////////////////////////////////////////////
36
37extern char * lock_type_str[];          // allocated in kernel_init.c
38
39
40//////////////////////////////////
41void rwlock_init( rwlock_t * lock,
42                  uint32_t   type )
43{ 
44        lock->taken   = 0;
45    lock->count   = 0;
46
47    list_root_init( &lock->rd_root );
48    list_root_init( &lock->wr_root );
49
50    busylock_init( &lock->lock , type );
51
52#if DEBUG_RWLOCK
53thread_t * this = CURRENT_THREAD;
54if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
55printk("\n[%s] thread[%x,%x] initialise lock %s [%x,%x]\n",
56__FUNCTION__, this->process->pid, this->trdid,
57lock_type_str[type], local_cxy, lock );
58#endif
59
60}
61
62/////////////////////////////////////////
63void rwlock_rd_acquire( rwlock_t * lock )
64{
65    thread_t * this = CURRENT_THREAD;
66
67    // check calling thread can yield
68    thread_assert_can_yield( this , __FUNCTION__ );
69
70    // get busylock
71    busylock_acquire( &lock->lock );
72
73    // block and deschedule if lock already taken
74    while( lock->taken )
75    {
76
77#if DEBUG_RWLOCK
78if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
79printk("\n[%s] thread[%x,%x] READ BLOCK on rwlock %s [%x,%x] / taken %d / count %d\n",
80__FUNCTION__, this->process->pid, this->trdid, 
81lock_type_str[lock->lock.type], local_cxy, lock, lock->taken, lock->count );
82#endif
83        // register reader thread in waiting queue
84        list_add_last( &lock->rd_root , &this->wait_list );
85
86        // block reader thread
87        thread_block( XPTR( local_cxy , this ) , THREAD_BLOCKED_LOCK );
88       
89        // release busylock
90        busylock_release( &lock->lock );
91
92        // deschedule
93        sched_yield("reader wait rwlock");
94       
95        // get busylock
96        busylock_acquire( &lock->lock );
97    }
98
99    // increment number of readers
100    lock->count++;
101
102#if DEBUG_RWLOCK
103if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
104printk("\n[%s] thread[%x,%x] READ ACQUIRE rwlock %s [%x,%x] / taken %d / count %d\n",
105__FUNCTION__, this->process->pid, this->trdid, 
106lock_type_str[lock->lock.type], local_cxy, lock, lock->taken, lock->count );
107#endif
108
109    // release busylock
110    busylock_release( &lock->lock );
111
112}  // end rwlock_rd_acquire()
113
114/////////////////////////////////////////
115void rwlock_wr_acquire( rwlock_t * lock )
116{
117    thread_t * this = CURRENT_THREAD;
118
119    // check calling thread can yield
120    thread_assert_can_yield( this , __FUNCTION__ );
121
122    // get busylock
123    busylock_acquire( &lock->lock );
124
125    // block and deschedule if lock already taken or existing read access
126    while( lock->taken || lock->count )
127    {
128
129#if DEBUG_RWLOCK
130if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
131printk("\n[%s] thread[%x,%x] WRITE BLOCK on rwlock %s [%x,%x] / taken %d / count %d\n",
132__FUNCTION__, this->process->pid, this->trdid, 
133lock_type_str[lock->lock.type], local_cxy, lock, lock->taken, lock->count );
134#endif
135        // register writer in waiting queue
136        list_add_last( &lock->wr_root , &this->wait_list );
137
138        // block writer thread
139        thread_block( XPTR( local_cxy , this ) , THREAD_BLOCKED_LOCK );
140       
141        // release busylock
142        busylock_release( &lock->lock );
143
144        // deschedule
145        sched_yield("writer wait rwlock");
146       
147        // get busylock
148        busylock_acquire( &lock->lock );
149    }
150
151    // take the rwlock
152    lock->taken = 1;
153
154#if DEBUG_RWLOCK
155if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
156printk("\n[%s] thread[%x,%x] WRITE ACQUIRE rwlock %s [%x,%x] / taken %d / count %d\n",
157__FUNCTION__, this->process->pid, this->trdid, 
158lock_type_str[lock->lock.type], local_cxy, lock, lock->taken, lock->count );
159#endif
160
161    // release busylock
162    busylock_release( &lock->lock );
163
164}  // end rwlock_wr_acquire()
165
166/////////////////////////////////////////
167void rwlock_rd_release( rwlock_t * lock )
168{
169    // synchronize memory before lock release
170    hal_fence();
171
172    // get busylock
173    busylock_acquire( &lock->lock );
174
175    // decrement number of readers
176    lock->count--;
177
178#if DEBUG_RWLOCK
179thread_t * this = CURRENT_THREAD;
180if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
181printk("\n[%s] thread[%x,%x] READ RELEASE rwlock %s [%x,%x] / taken %d / count %d\n",
182__FUNCTION__, this->process->pid, this->trdid, 
183lock_type_str[lock->lock.type], local_cxy, lock, lock->taken, lock->count );
184#endif
185
186    // release first writer in waiting queue if no current readers
187    // and writers waiting queue non empty
188    if( (lock->count == 0) && (list_is_empty( &lock->wr_root ) == false) )
189    {
190        // get first writer thread
191        thread_t * thread = LIST_FIRST( &lock->wr_root , thread_t , wait_list );
192
193#if DEBUG_RWLOCK
194if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
195printk("\n[%s] thread[%x,%x] UNBLOCK thread[%x,%x] / rwlock %s [%x,%x]\n",
196__FUNCTION__, this->process->pid, this->trdid, thread->process->pid, thread->trdid,
197lock_type_str[lock->lock.type], local_cxy, lock );
198#endif
199
200        // remove this waiting thread from waiting list
201        list_unlink( &thread->wait_list );
202
203        // unblock this waiting thread
204        thread_unblock( XPTR( local_cxy , thread ) , THREAD_BLOCKED_LOCK );
205    }
206    // release all readers in waiting queue if writers waiting queue empty
207    // and readers waiting queue non empty
208    else if( list_is_empty( &lock->wr_root ) && (list_is_empty( &lock->rd_root ) == false) )
209    {
210        while( list_is_empty( &lock->rd_root ) == false )
211        {
212            // get first reader thread
213            thread_t * thread = LIST_FIRST( &lock->wr_root , thread_t , wait_list );
214
215#if DEBUG_RWLOCK
216if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
217printk("\n[%s] thread[%x,%x] UNBLOCK thread[%x,%x] / rwlock %s [%x,%x]\n",
218__FUNCTION__, this->process->pid, this->trdid, thread->process->pid, thread->trdid,
219lock_type_str[lock->lock.type], local_cxy, lock );
220#endif
221   
222            // remove this waiting thread from waiting list
223            list_unlink( &thread->wait_list );
224
225            // unblock this waiting thread
226            thread_unblock( XPTR( local_cxy , thread ) , THREAD_BLOCKED_LOCK );
227        }
228    }
229
230    // release busylock
231    busylock_release( &lock->lock );
232
233}  // end rwlock_rd_release()
234
235/////////////////////////////////////////
236void rwlock_wr_release( rwlock_t * lock )
237{
238    // synchronize memory before lock release
239    hal_fence();
240
241    // get busylock
242    busylock_acquire( &lock->lock );
243
244    // release the rwlock
245    lock->taken = 0;
246
247#if DEBUG_RWLOCK
248thread_t * this = CURRENT_THREAD;
249if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
250printk("\n[%s] thread[%x,%x] WRITE RELEASE rwlock %s [%x,%x] / taken %d / count %d\n",
251__FUNCTION__, this->process->pid, this->trdid, 
252lock_type_str[lock->lock.type], local_cxy, lock, lock->taken, lock->count );
253#endif
254
255    // release first waiting writer thread if writers waiting queue non empty
256    if( list_is_empty( &lock->wr_root ) == false )
257    {
258        // get first writer thread
259        thread_t * thread = LIST_FIRST( &lock->wr_root , thread_t , wait_list );
260
261#if DEBUG_RWLOCK
262if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
263printk("\n[%s] thread[%x,%x] UNBLOCK thread[%x,%x] / rwlock %s [%x,%x]\n",
264__FUNCTION__, this->process->pid, this->trdid, thread->process->pid, thread->trdid,
265lock_type_str[lock->lock.type], local_cxy, lock );
266#endif
267        // remove this waiting thread from waiting list
268        list_unlink( &thread->wait_list );
269
270        // unblock this waiting thread
271        thread_unblock( XPTR( local_cxy , thread ) , THREAD_BLOCKED_LOCK );
272    }
273
274    // check readers waiting queue and release all if writers waiting queue empty
275    else 
276    {
277        while( list_is_empty( &lock->rd_root ) == false )
278        {
279            // get first reader thread
280            thread_t * thread = LIST_FIRST( &lock->rd_root , thread_t , wait_list );
281
282#if DEBUG_RWLOCK
283if( DEBUG_RWLOCK < (uint32_t)hal_get_cycles() )
284printk("\n[%s] thread[%x,%x] UNBLOCK thread[%x,%x] / rwlock %s [%x,%x]\n",
285__FUNCTION__, this->process->pid, this->trdid, thread->process->pid, thread->trdid,
286lock_type_str[lock->lock.type], local_cxy, lock );
287#endif
288            // remove this waiting thread from waiting list
289            list_unlink( &thread->wait_list );
290
291            // unblock this waiting thread
292            thread_unblock( XPTR( local_cxy , thread ) , THREAD_BLOCKED_LOCK );
293        }
294    }
295
296    // release busylock
297    busylock_release( &lock->lock );
298
299}  // end rwlock_wr_release()
300
301
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