1/* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements.  See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License.  You may obtain a copy of the License at
7 *
8 *     http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17/*Read/Write locking implementation based on the MultiLock code from
18 * Stephen Beaulieu <hippo@be.com>
19 */
20
21#include "apr_arch_thread_mutex.h"
22#include "apr_strings.h"
23#include "apr_portable.h"
24
25static apr_status_t _thread_mutex_cleanup(void * data)
26{
27    apr_thread_mutex_t *lock = (apr_thread_mutex_t*)data;
28    if (lock->LockCount != 0) {
29        /* we're still locked... */
30    	while (atomic_add(&lock->LockCount , -1) > 1){
31    	    /* OK we had more than one person waiting on the lock so
32    	     * the sem is also locked. Release it until we have no more
33    	     * locks left.
34    	     */
35            release_sem (lock->Lock);
36    	}
37    }
38    delete_sem(lock->Lock);
39    return APR_SUCCESS;
40}
41
42APR_DECLARE(apr_status_t) apr_thread_mutex_create(apr_thread_mutex_t **mutex,
43                                                  unsigned int flags,
44                                                  apr_pool_t *pool)
45{
46    apr_thread_mutex_t *new_m;
47    apr_status_t stat = APR_SUCCESS;
48
49    new_m = (apr_thread_mutex_t *)apr_pcalloc(pool, sizeof(apr_thread_mutex_t));
50    if (new_m == NULL){
51        return APR_ENOMEM;
52    }
53
54    if ((stat = create_sem(0, "APR_Lock")) < B_NO_ERROR) {
55        _thread_mutex_cleanup(new_m);
56        return stat;
57    }
58    new_m->LockCount = 0;
59    new_m->Lock = stat;
60    new_m->pool  = pool;
61
62    /* Optimal default is APR_THREAD_MUTEX_UNNESTED,
63     * no additional checks required for either flag.
64     */
65    new_m->nested = flags & APR_THREAD_MUTEX_NESTED;
66
67    apr_pool_cleanup_register(new_m->pool, (void *)new_m, _thread_mutex_cleanup,
68                              apr_pool_cleanup_null);
69
70    (*mutex) = new_m;
71    return APR_SUCCESS;
72}
73
74#if APR_HAS_CREATE_LOCKS_NP
75APR_DECLARE(apr_status_t) apr_thread_mutex_create_np(apr_thread_mutex_t **mutex,
76                                                   const char *fname,
77                                                   apr_lockmech_e_np mech,
78                                                   apr_pool_t *pool)
79{
80    return APR_ENOTIMPL;
81}
82#endif
83
84APR_DECLARE(apr_status_t) apr_thread_mutex_lock(apr_thread_mutex_t *mutex)
85{
86    int32 stat;
87    thread_id me = find_thread(NULL);
88
89    if (mutex->nested && mutex->owner == me) {
90        mutex->owner_ref++;
91        return APR_SUCCESS;
92    }
93
94	if (atomic_add(&mutex->LockCount, 1) > 0) {
95		if ((stat = acquire_sem(mutex->Lock)) < B_NO_ERROR) {
96            /* Oh dear, acquire_sem failed!!  */
97		    atomic_add(&mutex->LockCount, -1);
98		    return stat;
99		}
100	}
101
102    mutex->owner = me;
103    mutex->owner_ref = 1;
104
105    return APR_SUCCESS;
106}
107
108APR_DECLARE(apr_status_t) apr_thread_mutex_trylock(apr_thread_mutex_t *mutex)
109{
110    return APR_ENOTIMPL;
111}
112
113APR_DECLARE(apr_status_t) apr_thread_mutex_unlock(apr_thread_mutex_t *mutex)
114{
115    int32 stat;
116
117    if (mutex->nested && mutex->owner == find_thread(NULL)) {
118        mutex->owner_ref--;
119        if (mutex->owner_ref > 0)
120            return APR_SUCCESS;
121    }
122
123	if (atomic_add(&mutex->LockCount, -1) > 1) {
124        if ((stat = release_sem(mutex->Lock)) < B_NO_ERROR) {
125            atomic_add(&mutex->LockCount, 1);
126            return stat;
127        }
128    }
129
130    mutex->owner = -1;
131    mutex->owner_ref = 0;
132
133    return APR_SUCCESS;
134}
135
136APR_DECLARE(apr_status_t) apr_thread_mutex_destroy(apr_thread_mutex_t *mutex)
137{
138    apr_status_t stat;
139    if ((stat = _thread_mutex_cleanup(mutex)) == APR_SUCCESS) {
140        apr_pool_cleanup_kill(mutex->pool, mutex, _thread_mutex_cleanup);
141        return APR_SUCCESS;
142    }
143    return stat;
144}
145
146APR_POOL_IMPLEMENT_ACCESSOR(thread_mutex)
147
148