1 /*
2 * pte_threadReuse.c
3 *
4 * Description:
5 * This translation unit implements miscellaneous thread functions.
6 *
7 * --------------------------------------------------------------------------
8 *
9 * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
10 * Copyright(C) 2008 Jason Schmidlapp
11 *
12 * Contact Email: jschmidlapp@users.sourceforge.net
13 *
14 *
15 * Based upon Pthreads-win32 - POSIX Threads Library for Win32
16 * Copyright(C) 1998 John E. Bossom
17 * Copyright(C) 1999,2005 Pthreads-win32 contributors
18 *
19 * Contact Email: rpj@callisto.canberra.edu.au
20 *
21 * The original list of contributors to the Pthreads-win32 project
22 * is contained in the file CONTRIBUTORS.ptw32 included with the
23 * source code distribution. The list can also be seen at the
24 * following World Wide Web location:
25 * http://sources.redhat.com/pthreads-win32/contributors.html
26 *
27 * This library is free software; you can redistribute it and/or
28 * modify it under the terms of the GNU Lesser General Public
29 * License as published by the Free Software Foundation; either
30 * version 2 of the License, or (at your option) any later version.
31 *
32 * This library is distributed in the hope that it will be useful,
33 * but WITHOUT ANY WARRANTY; without even the implied warranty of
34 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
35 * Lesser General Public License for more details.
36 *
37 * You should have received a copy of the GNU Lesser General Public
38 * License along with this library in the file COPYING.LIB;
39 * if not, write to the Free Software Foundation, Inc.,
40 * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
41 */
42
43 #include <stdio.h>
44 #include <stdlib.h>
45 #include <string.h>
46
47 #include "pthread.h"
48 #include "implement.h"
49
50
51 /*
52 * How it works:
53 * A pthread_t is a struct which is normally passed/returned by
54 * value to/from pthreads routines. Applications are therefore storing
55 * a copy of the struct as it is at that time.
56 *
57 * The original pthread_t struct plus all copies of it contain the address of
58 * the thread state struct pte_thread_t_ (p), plus a reuse counter (x). Each
59 * pte_thread_t contains the original copy of it's pthread_t.
60 * Once malloced, a pte_thread_t_ struct is not freed until the process exits.
61 *
62 * The thread reuse stack is a simple LILO stack managed through a singly
63 * linked list element in the pte_thread_t.
64 *
65 * Each time a thread is destroyed, the pte_thread_t address is pushed onto the
66 * reuse stack after it's ptHandle's reuse counter has been incremented.
67 *
68 * The following can now be said from this:
69 * - two pthread_t's are identical if their pte_thread_t reference pointers
70 * are equal and their reuse counters are equal. That is,
71 *
72 * equal = (a.p == b.p && a.x == b.x)
73 *
74 * - a pthread_t copy refers to a destroyed thread if the reuse counter in
75 * the copy is not equal to the reuse counter in the original.
76 *
77 * threadDestroyed = (copy.x != ((pte_thread_t *)copy.p)->ptHandle.x)
78 *
79 */
80
81 /*
82 * Pop a clean pthread_t struct off the reuse stack.
83 */
84 pthread_t
pte_threadReusePop(void)85 pte_threadReusePop (void)
86 {
87 pthread_t t = NULL;
88
89
90 pte_osMutexLock (pte_thread_reuse_lock);
91
92 if (PTE_THREAD_REUSE_EMPTY != pte_threadReuseTop)
93 {
94 pte_thread_t * tp;
95
96 tp = pte_threadReuseTop;
97
98 pte_threadReuseTop = tp->prevReuse;
99
100 if (PTE_THREAD_REUSE_EMPTY == pte_threadReuseTop)
101 {
102 pte_threadReuseBottom = PTE_THREAD_REUSE_EMPTY;
103 }
104
105 tp->prevReuse = NULL;
106
107 t = tp->ptHandle;
108 }
109
110 pte_osMutexUnlock(pte_thread_reuse_lock);
111
112 return t;
113
114 }
115
116 /*
117 * Push a clean pthread_t struct onto the reuse stack.
118 * Must be re-initialised when reused.
119 * All object elements (mutexes, events etc) must have been either
120 * detroyed before this, or never initialised.
121 */
122 void
pte_threadReusePush(pthread_t thread)123 pte_threadReusePush (pthread_t thread)
124 {
125 pte_thread_t * tp = (pte_thread_t *) thread;
126 pthread_t t;
127
128
129 pte_osMutexLock (pte_thread_reuse_lock);
130
131 t = tp->ptHandle;
132 memset(tp, 0, sizeof(pte_thread_t));
133
134 /* Must restore the original POSIX handle that we just wiped. */
135 tp->ptHandle = t;
136
137 tp->prevReuse = PTE_THREAD_REUSE_EMPTY;
138
139 if (PTE_THREAD_REUSE_EMPTY != pte_threadReuseBottom)
140 {
141 pte_threadReuseBottom->prevReuse = tp;
142 }
143 else
144 {
145 pte_threadReuseTop = tp;
146 }
147
148 pte_threadReuseBottom = tp;
149
150 pte_osMutexUnlock(pte_thread_reuse_lock);
151 }
152