source: trunk/kernel/libk/remote_rwlock.h @ 444

Last change on this file since 444 was 438, checked in by alain, 7 years ago

Fix a bug in scheduler related to RPC blocking.
File size: 5.3 KB
Line 
1/*
2 * remote_rwlock.h - kernel remote_rwlock definition.
3 *
4 * Authors   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#ifndef _REMOTE_RWLOCK_H_
25#define _REMOTE_RWLOCK_H_
26
27#include <kernel_config.h>
28#include <hal_types.h>
29#include <xlist.h>
30
31/***************************************************************************************
32 * This file defines a remote kernel lock, that supports several simultaneous read
33 * accesses, but only one write access. It implements a ticket based allocation policy.
34 * It can be used to synchronize threads running in different clusters, because
35 * all access functions use remote pointers.
36 * - A reader take the lock to atomically increments the registered readers count.
37 *   Then it release the lock and access the protected structure. It atomically
38 *   decrements the readers count without taking the lock when access is completed.
39 * - A writer take the lock and keep it, but must wait completion of all current read
40 *   accesses before starting its own access.
41 * When the lock is taken by another thread, the new-comers use a busy waiting policy.
42 **************************************************************************************/
43
44typedef struct remote_rwlock_s
45{
46    uint32_t       ticket;          /*! first free ticket index                       */
47    uint32_t       current;         /*! ticket index of current owner                 */
48    uint32_t       count;           /*! current number of reader threads              */
49
50#if DEBUG_REMOTE_RWLOCKS
51    xptr_t         owner;           /*! extended pointer on writer thread             */
52    xlist_entry_t  list;            /*! member of list of remote locks taken by owner */
53#endif
54
55} 
56remote_rwlock_t;
57
58/***************************************************************************************
59 * This function initializes a remote rwlock.
60 ***************************************************************************************
61 * @ lock_xp    : extended pointer on the remote rwlock
62 **************************************************************************************/
63void remote_rwlock_init( xptr_t lock_xp );
64
65/***************************************************************************************
66 * This blocking function get access to a remote rwlock for a reader.
67 * It increments the calling thread locks count when the lock has been taken.
68 ***************************************************************************************
69 * @ lock_xp    : extended pointer on the remote rwlock
70 **************************************************************************************/
71void remote_rwlock_rd_lock( xptr_t lock_xp );
72
73/***************************************************************************************
74 * This function releases a remote rwlock for a reader.
75 * It decrements the calling thread locks count when the lock has been released.
76 ***************************************************************************************
77 * @ lock_xp    : extended pointer on the remote rwlock
78 **************************************************************************************/
79void remote_rwlock_rd_unlock( xptr_t lock_xp );
80
81/***************************************************************************************
82 * This blocking function get access to a remote rwlock for a writer.
83 * It increments the calling thread locks count when the lock has been taken.
84 ***************************************************************************************
85 * @ lock_xp    : extended pointer on the remote rwlock
86 **************************************************************************************/
87void remote_rwlock_wr_lock( xptr_t lock_xp );
88
89/***************************************************************************************
90 * This function releases a remote rwlock for a writer.
91 * It decrements the calling thread locks count when the lock has been released.
92 ***************************************************************************************
93 * @ lock_xp    : extended pointer on the remote rwlock
94 **************************************************************************************/
95void remote_rwlock_wr_unlock( xptr_t lock_xp );
96
97/***************************************************************************************
98 * Display the lock state on kernel TTY.
99 ***************************************************************************************
100 * @ lock_xp    : extended pointer on the remote rwlock
101 * @ comment    : comment to be printed.
102 **************************************************************************************/
103void remote_rwlock_print( xptr_t   lock_xp,
104                          char   * comment );
105
106#endif
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