1 /*
2 * pthread_mutex_trylock.c
3 *
4 * Description:
5 * This translation unit implements mutual exclusion (mutex) primitives.
6 *
7 * --------------------------------------------------------------------------
8 *
9 * Pthreads-win32 - POSIX Threads Library for Win32
10 * Copyright(C) 1998 John E. Bossom
11 * Copyright(C) 1999,2005 Pthreads-win32 contributors
12 *
13 * Contact Email: rpj@callisto.canberra.edu.au
14 *
15 * The current list of contributors is contained
16 * in the file CONTRIBUTORS included with the source
17 * code distribution. The list can also be seen at the
18 * following World Wide Web location:
19 * http://sources.redhat.com/pthreads-win32/contributors.html
20 *
21 * This library is free software; you can redistribute it and/or
22 * modify it under the terms of the GNU Lesser General Public
23 * License as published by the Free Software Foundation; either
24 * version 2 of the License, or (at your option) any later version.
25 *
26 * This library is distributed in the hope that it will be useful,
27 * but WITHOUT ANY WARRANTY; without even the implied warranty of
28 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
29 * Lesser General Public License for more details.
30 *
31 * You should have received a copy of the GNU Lesser General Public
32 * License along with this library in the file COPYING.LIB;
33 * if not, write to the Free Software Foundation, Inc.,
34 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
35 */
36
37 #include "pthread.h"
38 #include "implement.h"
39
40
41 int
pthread_mutex_trylock(pthread_mutex_t * mutex)42 pthread_mutex_trylock (pthread_mutex_t * mutex)
43 {
44 pthread_mutex_t mx;
45 int kind;
46 int result = 0;
47
48 /*
49 * Let the system deal with invalid pointers.
50 */
51
52 /*
53 * We do a quick check to see if we need to do more work
54 * to initialise a static mutex. We check
55 * again inside the guarded section of ptw32_mutex_check_need_init()
56 * to avoid race conditions.
57 */
58 if (*mutex >= PTHREAD_ERRORCHECK_MUTEX_INITIALIZER)
59 {
60 if ((result = ptw32_mutex_check_need_init (mutex)) != 0)
61 {
62 return (result);
63 }
64 }
65
66 mx = *mutex;
67 kind = mx->kind;
68
69 if (kind >= 0)
70 {
71 /* Non-robust */
72 if (0 == (PTW32_INTERLOCKED_LONG) PTW32_INTERLOCKED_COMPARE_EXCHANGE_LONG (
73 (PTW32_INTERLOCKED_LONGPTR) &mx->lock_idx,
74 (PTW32_INTERLOCKED_LONG) 1,
75 (PTW32_INTERLOCKED_LONG) 0))
76 {
77 if (kind != PTHREAD_MUTEX_NORMAL)
78 {
79 mx->recursive_count = 1;
80 mx->ownerThread = pthread_self ();
81 }
82 }
83 else
84 {
85 if (kind == PTHREAD_MUTEX_RECURSIVE &&
86 pthread_equal (mx->ownerThread, pthread_self ()))
87 {
88 mx->recursive_count++;
89 }
90 else
91 {
92 result = EBUSY;
93 }
94 }
95 }
96 else
97 {
98 /*
99 * Robust types
100 * All types record the current owner thread.
101 * The mutex is added to a per thread list when ownership is acquired.
102 */
103 pthread_t self;
104 ptw32_robust_state_t* statePtr = &mx->robustNode->stateInconsistent;
105
106 if ((PTW32_INTERLOCKED_LONG)PTW32_ROBUST_NOTRECOVERABLE ==
107 PTW32_INTERLOCKED_EXCHANGE_ADD_LONG(
108 (PTW32_INTERLOCKED_LONGPTR)statePtr,
109 (PTW32_INTERLOCKED_LONG)0))
110 {
111 return ENOTRECOVERABLE;
112 }
113
114 self = pthread_self();
115 kind = -kind - 1; /* Convert to non-robust range */
116
117 if (0 == (PTW32_INTERLOCKED_LONG) PTW32_INTERLOCKED_COMPARE_EXCHANGE_LONG (
118 (PTW32_INTERLOCKED_LONGPTR) &mx->lock_idx,
119 (PTW32_INTERLOCKED_LONG) 1,
120 (PTW32_INTERLOCKED_LONG) 0))
121 {
122 if (kind != PTHREAD_MUTEX_NORMAL)
123 {
124 mx->recursive_count = 1;
125 }
126 ptw32_robust_mutex_add(mutex, self);
127 }
128 else
129 {
130 if (PTHREAD_MUTEX_RECURSIVE == kind &&
131 pthread_equal (mx->ownerThread, pthread_self ()))
132 {
133 mx->recursive_count++;
134 }
135 else
136 {
137 if (EOWNERDEAD == (result = ptw32_robust_mutex_inherit(mutex)))
138 {
139 mx->recursive_count = 1;
140 ptw32_robust_mutex_add(mutex, self);
141 }
142 else
143 {
144 if (0 == result)
145 {
146 result = EBUSY;
147 }
148 }
149 }
150 }
151 }
152
153 return (result);
154 }
155