1*062c5bc4SJason Schmidlapp /*
2*062c5bc4SJason Schmidlapp * pthread_rwlock_trywrlock.c
3*062c5bc4SJason Schmidlapp *
4*062c5bc4SJason Schmidlapp * Description:
5*062c5bc4SJason Schmidlapp * This translation unit implements read/write lock primitives.
6*062c5bc4SJason Schmidlapp *
7*062c5bc4SJason Schmidlapp * --------------------------------------------------------------------------
8*062c5bc4SJason Schmidlapp *
9*062c5bc4SJason Schmidlapp * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
10*062c5bc4SJason Schmidlapp * Copyright(C) 2008 Jason Schmidlapp
11*062c5bc4SJason Schmidlapp *
12*062c5bc4SJason Schmidlapp * Contact Email: jschmidlapp@users.sourceforge.net
13*062c5bc4SJason Schmidlapp *
14*062c5bc4SJason Schmidlapp *
15*062c5bc4SJason Schmidlapp * Based upon Pthreads-win32 - POSIX Threads Library for Win32
16*062c5bc4SJason Schmidlapp * Copyright(C) 1998 John E. Bossom
17*062c5bc4SJason Schmidlapp * Copyright(C) 1999,2005 Pthreads-win32 contributors
18*062c5bc4SJason Schmidlapp *
19*062c5bc4SJason Schmidlapp * Contact Email: rpj@callisto.canberra.edu.au
20*062c5bc4SJason Schmidlapp *
21*062c5bc4SJason Schmidlapp * The original list of contributors to the Pthreads-win32 project
22*062c5bc4SJason Schmidlapp * is contained in the file CONTRIBUTORS.ptw32 included with the
23*062c5bc4SJason Schmidlapp * source code distribution. The list can also be seen at the
24*062c5bc4SJason Schmidlapp * following World Wide Web location:
25*062c5bc4SJason Schmidlapp * http://sources.redhat.com/pthreads-win32/contributors.html
26*062c5bc4SJason Schmidlapp *
27*062c5bc4SJason Schmidlapp * This library is free software; you can redistribute it and/or
28*062c5bc4SJason Schmidlapp * modify it under the terms of the GNU Lesser General Public
29*062c5bc4SJason Schmidlapp * License as published by the Free Software Foundation; either
30*062c5bc4SJason Schmidlapp * version 2 of the License, or (at your option) any later version.
31*062c5bc4SJason Schmidlapp *
32*062c5bc4SJason Schmidlapp * This library is distributed in the hope that it will be useful,
33*062c5bc4SJason Schmidlapp * but WITHOUT ANY WARRANTY; without even the implied warranty of
34*062c5bc4SJason Schmidlapp * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
35*062c5bc4SJason Schmidlapp * Lesser General Public License for more details.
36*062c5bc4SJason Schmidlapp *
37*062c5bc4SJason Schmidlapp * You should have received a copy of the GNU Lesser General Public
38*062c5bc4SJason Schmidlapp * License along with this library in the file COPYING.LIB;
39*062c5bc4SJason Schmidlapp * if not, write to the Free Software Foundation, Inc.,
40*062c5bc4SJason Schmidlapp * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
41*062c5bc4SJason Schmidlapp */
42*062c5bc4SJason Schmidlapp
43*062c5bc4SJason Schmidlapp #include <errno.h>
44*062c5bc4SJason Schmidlapp #include <limits.h>
45*062c5bc4SJason Schmidlapp
46*062c5bc4SJason Schmidlapp #include "pthread.h"
47*062c5bc4SJason Schmidlapp #include "implement.h"
48*062c5bc4SJason Schmidlapp
49*062c5bc4SJason Schmidlapp int
pthread_rwlock_trywrlock(pthread_rwlock_t * rwlock)50*062c5bc4SJason Schmidlapp pthread_rwlock_trywrlock (pthread_rwlock_t * rwlock)
51*062c5bc4SJason Schmidlapp {
52*062c5bc4SJason Schmidlapp int result, result1;
53*062c5bc4SJason Schmidlapp pthread_rwlock_t rwl;
54*062c5bc4SJason Schmidlapp
55*062c5bc4SJason Schmidlapp if (rwlock == NULL || *rwlock == NULL)
56*062c5bc4SJason Schmidlapp {
57*062c5bc4SJason Schmidlapp return EINVAL;
58*062c5bc4SJason Schmidlapp }
59*062c5bc4SJason Schmidlapp
60*062c5bc4SJason Schmidlapp /*
61*062c5bc4SJason Schmidlapp * We do a quick check to see if we need to do more work
62*062c5bc4SJason Schmidlapp * to initialise a static rwlock. We check
63*062c5bc4SJason Schmidlapp * again inside the guarded section of pte_rwlock_check_need_init()
64*062c5bc4SJason Schmidlapp * to avoid race conditions.
65*062c5bc4SJason Schmidlapp */
66*062c5bc4SJason Schmidlapp if (*rwlock == PTHREAD_RWLOCK_INITIALIZER)
67*062c5bc4SJason Schmidlapp {
68*062c5bc4SJason Schmidlapp result = pte_rwlock_check_need_init (rwlock);
69*062c5bc4SJason Schmidlapp
70*062c5bc4SJason Schmidlapp if (result != 0 && result != EBUSY)
71*062c5bc4SJason Schmidlapp {
72*062c5bc4SJason Schmidlapp return result;
73*062c5bc4SJason Schmidlapp }
74*062c5bc4SJason Schmidlapp }
75*062c5bc4SJason Schmidlapp
76*062c5bc4SJason Schmidlapp rwl = *rwlock;
77*062c5bc4SJason Schmidlapp
78*062c5bc4SJason Schmidlapp if (rwl->nMagic != PTE_RWLOCK_MAGIC)
79*062c5bc4SJason Schmidlapp {
80*062c5bc4SJason Schmidlapp return EINVAL;
81*062c5bc4SJason Schmidlapp }
82*062c5bc4SJason Schmidlapp
83*062c5bc4SJason Schmidlapp if ((result = pthread_mutex_trylock (&(rwl->mtxExclusiveAccess))) != 0)
84*062c5bc4SJason Schmidlapp {
85*062c5bc4SJason Schmidlapp return result;
86*062c5bc4SJason Schmidlapp }
87*062c5bc4SJason Schmidlapp
88*062c5bc4SJason Schmidlapp if ((result =
89*062c5bc4SJason Schmidlapp pthread_mutex_trylock (&(rwl->mtxSharedAccessCompleted))) != 0)
90*062c5bc4SJason Schmidlapp {
91*062c5bc4SJason Schmidlapp result1 = pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
92*062c5bc4SJason Schmidlapp return ((result1 != 0) ? result1 : result);
93*062c5bc4SJason Schmidlapp }
94*062c5bc4SJason Schmidlapp
95*062c5bc4SJason Schmidlapp if (rwl->nExclusiveAccessCount == 0)
96*062c5bc4SJason Schmidlapp {
97*062c5bc4SJason Schmidlapp if (rwl->nCompletedSharedAccessCount > 0)
98*062c5bc4SJason Schmidlapp {
99*062c5bc4SJason Schmidlapp rwl->nSharedAccessCount -= rwl->nCompletedSharedAccessCount;
100*062c5bc4SJason Schmidlapp rwl->nCompletedSharedAccessCount = 0;
101*062c5bc4SJason Schmidlapp }
102*062c5bc4SJason Schmidlapp
103*062c5bc4SJason Schmidlapp if (rwl->nSharedAccessCount > 0)
104*062c5bc4SJason Schmidlapp {
105*062c5bc4SJason Schmidlapp if ((result =
106*062c5bc4SJason Schmidlapp pthread_mutex_unlock (&(rwl->mtxSharedAccessCompleted))) != 0)
107*062c5bc4SJason Schmidlapp {
108*062c5bc4SJason Schmidlapp (void) pthread_mutex_unlock (&(rwl->mtxExclusiveAccess));
109*062c5bc4SJason Schmidlapp return result;
110*062c5bc4SJason Schmidlapp }
111*062c5bc4SJason Schmidlapp
112*062c5bc4SJason Schmidlapp if ((result =
113*062c5bc4SJason Schmidlapp pthread_mutex_unlock (&(rwl->mtxExclusiveAccess))) == 0)
114*062c5bc4SJason Schmidlapp {
115*062c5bc4SJason Schmidlapp result = EBUSY;
116*062c5bc4SJason Schmidlapp }
117*062c5bc4SJason Schmidlapp }
118*062c5bc4SJason Schmidlapp else
119*062c5bc4SJason Schmidlapp {
120*062c5bc4SJason Schmidlapp rwl->nExclusiveAccessCount = 1;
121*062c5bc4SJason Schmidlapp }
122*062c5bc4SJason Schmidlapp }
123*062c5bc4SJason Schmidlapp else
124*062c5bc4SJason Schmidlapp {
125*062c5bc4SJason Schmidlapp result = EBUSY;
126*062c5bc4SJason Schmidlapp }
127*062c5bc4SJason Schmidlapp
128*062c5bc4SJason Schmidlapp return result;
129*062c5bc4SJason Schmidlapp }
130