source: trunk/kernel/libk/busylock.c

Last change on this file was 666, checked in by alain, 13 months ago

Cosmetic.

File size: 3.8 KB
Line 
1/*
2 * busylock.c - local kernel busy waiting lock implementation.
3 *
4 * Authors     Alain Greiner (2016,2017,2018,2019,2020)
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_irqmask.h>
27#include <hal_special.h>
28#include <hal_atomic.h>
29#include <thread.h>
30#include <busylock.h>
31
32//////////////////////////////////////////////////////////////////////////////
33//                Extern global variables
34//////////////////////////////////////////////////////////////////////////////
35
36extern char               * lock_type_str[];    // allocated in kernel_init.c
37extern chdev_directory_t    chdev_dir;          // allocated in kernel_init.c
38
39//////////////////////////////////////
40void busylock_init( busylock_t * lock,
41                    uint32_t     type )
42{
43    lock->ticket  = 0;
44    lock->current = 0;
45    lock->type    = type;
46
47#if DEBUG_BUSYLOCK_TYPE
48    xlist_entry_init( XPTR( local_cxy , &lock->xlist ) ); 
49#endif
50
51}
52
53//////////////////////////////////////////
54void busylock_acquire( busylock_t * lock )
55{
56    reg_t      save_sr;
57    thread_t * this = CURRENT_THREAD;
58
59    // enter critical section
60    hal_disable_irq( &save_sr );
61 
62    // get one free ticket and update ticket allocator
63    uint32_t ticket = hal_atomic_add( &lock->ticket , 1 );
64
65    // poll current until success
66    while( lock->current != ticket )  asm volatile ("nop");
67
68    // increment thread locks counter
69    this->busylocks++;
70
71    // save SR in lock descriptor
72    lock->save_sr = save_sr;
73
74    // memory barrier to update lock and thread state
75    hal_fence();
76
77#if DEBUG_BUSYLOCK
78if( lock->type != LOCK_CHDEV_TXT0 ) 
79{
80    // update thread list of busylocks
81    xptr_t root_xp = XPTR( local_cxy , &this->busylocks_root );
82    xlist_add_last( root_xp , XPTR( local_cxy , &lock->xlist ) );
83}
84#endif
85
86#if( DEBUG_BUSYLOCK & 1 )
87if( (lock->type != LOCK_CHDEV_TXT0) && 
88    (this->process->pid == DEBUG_BUSYLOCK_PID) &&
89    (this->trdid == DEBUG_BUSYLOCK_TRDID) )
90{
91    printk("\n[%s] thread[%x,%x] ACQUIRE lock %s\n",
92    __FUNCTION__, this->process->pid, this->trdid, lock_type_str[lock->type] );
93}
94#endif
95
96} // end busylock_acquire()
97
98//////////////////////////////////////////
99void busylock_release( busylock_t * lock )
100{
101    thread_t * this = CURRENT_THREAD;
102
103    // memory barrier to update the protected object
104    hal_fence();
105
106    // update lock state
107    lock->current++;
108
109    // decrement thread busylocks counter
110    this->busylocks--;
111
112    // memory barrier to update busylock and thread state
113    hal_fence();
114
115#if DEBUG_BUSYLOCK
116if( lock->type != LOCK_CHDEV_TXT0 ) 
117{
118    // remove lock from thread list of busylocks
119    xlist_unlink( XPTR( local_cxy , &lock->xlist ) );
120}
121#endif
122
123#if( DEBUG_BUSYLOCK & 1 )
124if( (lock->type != LOCK_CHDEV_TXT0) && 
125    (this->process->pid == DEBUG_BUSYLOCK_PID) &&
126    (this->trdid == DEBUG_BUSYLOCK_TRDID) )
127{
128    printk("\n[%s] thread[%x,%x] RELEASE lock %s\n",
129    __FUNCTION__, this->process->pid, this->trdid, lock_type_str[lock->type] );
130}
131#endif
132
133    // exit critical section
134    hal_restore_irq( lock->save_sr );
135 
136}  // end busylock_release()
137
138       
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