1*062c5bc4SJason Schmidlapp /*
2*062c5bc4SJason Schmidlapp * pte_cond_check_need_init.c
3*062c5bc4SJason Schmidlapp *
4*062c5bc4SJason Schmidlapp * Description:
5*062c5bc4SJason Schmidlapp * This translation unit implements condition variables and their primitives.
6*062c5bc4SJason Schmidlapp *
7*062c5bc4SJason Schmidlapp *
8*062c5bc4SJason Schmidlapp * --------------------------------------------------------------------------
9*062c5bc4SJason Schmidlapp *
10*062c5bc4SJason Schmidlapp * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
11*062c5bc4SJason Schmidlapp * Copyright(C) 2008 Jason Schmidlapp
12*062c5bc4SJason Schmidlapp *
13*062c5bc4SJason Schmidlapp * Contact Email: jschmidlapp@users.sourceforge.net
14*062c5bc4SJason Schmidlapp *
15*062c5bc4SJason Schmidlapp *
16*062c5bc4SJason Schmidlapp * Based upon Pthreads-win32 - POSIX Threads Library for Win32
17*062c5bc4SJason Schmidlapp * Copyright(C) 1998 John E. Bossom
18*062c5bc4SJason Schmidlapp * Copyright(C) 1999,2005 Pthreads-win32 contributors
19*062c5bc4SJason Schmidlapp *
20*062c5bc4SJason Schmidlapp * Contact Email: rpj@callisto.canberra.edu.au
21*062c5bc4SJason Schmidlapp *
22*062c5bc4SJason Schmidlapp * The original list of contributors to the Pthreads-win32 project
23*062c5bc4SJason Schmidlapp * is contained in the file CONTRIBUTORS.ptw32 included with the
24*062c5bc4SJason Schmidlapp * source code distribution. The list can also be seen at the
25*062c5bc4SJason Schmidlapp * following World Wide Web location:
26*062c5bc4SJason Schmidlapp * http://sources.redhat.com/pthreads-win32/contributors.html
27*062c5bc4SJason Schmidlapp *
28*062c5bc4SJason Schmidlapp * This library is free software; you can redistribute it and/or
29*062c5bc4SJason Schmidlapp * modify it under the terms of the GNU Lesser General Public
30*062c5bc4SJason Schmidlapp * License as published by the Free Software Foundation; either
31*062c5bc4SJason Schmidlapp * version 2 of the License, or (at your option) any later version.
32*062c5bc4SJason Schmidlapp *
33*062c5bc4SJason Schmidlapp * This library is distributed in the hope that it will be useful,
34*062c5bc4SJason Schmidlapp * but WITHOUT ANY WARRANTY; without even the implied warranty of
35*062c5bc4SJason Schmidlapp * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
36*062c5bc4SJason Schmidlapp * Lesser General Public License for more details.
37*062c5bc4SJason Schmidlapp *
38*062c5bc4SJason Schmidlapp * You should have received a copy of the GNU Lesser General Public
39*062c5bc4SJason Schmidlapp * License along with this library in the file COPYING.LIB;
40*062c5bc4SJason Schmidlapp * if not, write to the Free Software Foundation, Inc.,
41*062c5bc4SJason Schmidlapp * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
42*062c5bc4SJason Schmidlapp */
43*062c5bc4SJason Schmidlapp
44*062c5bc4SJason Schmidlapp #include "pthread.h"
45*062c5bc4SJason Schmidlapp #include "implement.h"
46*062c5bc4SJason Schmidlapp
47*062c5bc4SJason Schmidlapp
48*062c5bc4SJason Schmidlapp int
pte_cond_check_need_init(pthread_cond_t * cond)49*062c5bc4SJason Schmidlapp pte_cond_check_need_init (pthread_cond_t * cond)
50*062c5bc4SJason Schmidlapp {
51*062c5bc4SJason Schmidlapp int result = 0;
52*062c5bc4SJason Schmidlapp
53*062c5bc4SJason Schmidlapp /*
54*062c5bc4SJason Schmidlapp * The following guarded test is specifically for statically
55*062c5bc4SJason Schmidlapp * initialised condition variables (via PTHREAD_OBJECT_INITIALIZER).
56*062c5bc4SJason Schmidlapp *
57*062c5bc4SJason Schmidlapp * Note that by not providing this synchronisation we risk
58*062c5bc4SJason Schmidlapp * introducing race conditions into applications which are
59*062c5bc4SJason Schmidlapp * correctly written.
60*062c5bc4SJason Schmidlapp *
61*062c5bc4SJason Schmidlapp * Approach
62*062c5bc4SJason Schmidlapp * --------
63*062c5bc4SJason Schmidlapp * We know that static condition variables will not be PROCESS_SHARED
64*062c5bc4SJason Schmidlapp * so we can serialise access to internal state using
65*062c5bc4SJason Schmidlapp * Win32 Critical Sections rather than Win32 Mutexes.
66*062c5bc4SJason Schmidlapp *
67*062c5bc4SJason Schmidlapp * If using a single global lock slows applications down too much,
68*062c5bc4SJason Schmidlapp * multiple global locks could be created and hashed on some random
69*062c5bc4SJason Schmidlapp * value associated with each mutex, the pointer perhaps. At a guess,
70*062c5bc4SJason Schmidlapp * a good value for the optimal number of global locks might be
71*062c5bc4SJason Schmidlapp * the number of processors + 1.
72*062c5bc4SJason Schmidlapp *
73*062c5bc4SJason Schmidlapp */
74*062c5bc4SJason Schmidlapp
75*062c5bc4SJason Schmidlapp
76*062c5bc4SJason Schmidlapp pte_osMutexLock (pte_cond_test_init_lock);
77*062c5bc4SJason Schmidlapp
78*062c5bc4SJason Schmidlapp /*
79*062c5bc4SJason Schmidlapp * We got here possibly under race
80*062c5bc4SJason Schmidlapp * conditions. Check again inside the critical section.
81*062c5bc4SJason Schmidlapp * If a static cv has been destroyed, the application can
82*062c5bc4SJason Schmidlapp * re-initialise it only by calling pthread_cond_init()
83*062c5bc4SJason Schmidlapp * explicitly.
84*062c5bc4SJason Schmidlapp */
85*062c5bc4SJason Schmidlapp if (*cond == PTHREAD_COND_INITIALIZER)
86*062c5bc4SJason Schmidlapp {
87*062c5bc4SJason Schmidlapp result = pthread_cond_init (cond, NULL);
88*062c5bc4SJason Schmidlapp }
89*062c5bc4SJason Schmidlapp else if (*cond == NULL)
90*062c5bc4SJason Schmidlapp {
91*062c5bc4SJason Schmidlapp /*
92*062c5bc4SJason Schmidlapp * The cv has been destroyed while we were waiting to
93*062c5bc4SJason Schmidlapp * initialise it, so the operation that caused the
94*062c5bc4SJason Schmidlapp * auto-initialisation should fail.
95*062c5bc4SJason Schmidlapp */
96*062c5bc4SJason Schmidlapp result = EINVAL;
97*062c5bc4SJason Schmidlapp }
98*062c5bc4SJason Schmidlapp
99*062c5bc4SJason Schmidlapp
100*062c5bc4SJason Schmidlapp pte_osMutexUnlock(pte_cond_test_init_lock);
101*062c5bc4SJason Schmidlapp
102*062c5bc4SJason Schmidlapp return result;
103*062c5bc4SJason Schmidlapp }
104