1 /*
2 * pthread_timechange_handler_np.c
3 *
4 * Description:
5 * This translation unit implements miscellaneous thread functions.
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 * Notes on handling system time adjustments (especially negative ones).
42 * ---------------------------------------------------------------------
43 *
44 * This solution was suggested by Alexander Terekhov, but any errors
45 * in the implementation are mine - [Ross Johnson]
46 *
47 * 1) The problem: threads doing a timedwait on a CV may expect to timeout
48 * at a specific absolute time according to a system timer. If the
49 * system clock is adjusted backwards then those threads sleep longer than
50 * expected. Also, pthreads-win32 converts absolute times to intervals in
51 * order to make use of the underlying Win32, and so waiting threads may
52 * awake before their proper abstimes.
53 *
54 * 2) We aren't able to distinquish between threads on timed or untimed waits,
55 * so we wake them all at the time of the adjustment so that they can
56 * re-evaluate their conditions and re-compute their timeouts.
57 *
58 * 3) We rely on correctly written applications for this to work. Specifically,
59 * they must be able to deal properly with spurious wakeups. That is,
60 * they must re-test their condition upon wakeup and wait again if
61 * the condition is not satisfied.
62 */
63
64 void *
pthread_timechange_handler_np(void * arg)65 pthread_timechange_handler_np (void *arg)
66 /*
67 * ------------------------------------------------------
68 * DOCPUBLIC
69 * Broadcasts all CVs to force re-evaluation and
70 * new timeouts if required.
71 *
72 * PARAMETERS
73 * NONE
74 *
75 *
76 * DESCRIPTION
77 * Broadcasts all CVs to force re-evaluation and
78 * new timeouts if required.
79 *
80 * This routine may be passed directly to pthread_create()
81 * as a new thread in order to run asynchronously.
82 *
83 *
84 * RESULTS
85 * 0 successfully broadcast all CVs
86 * EAGAIN Not all CVs were broadcast
87 *
88 * ------------------------------------------------------
89 */
90 {
91 int result = 0;
92 pthread_cond_t cv;
93 ptw32_mcs_local_node_t node;
94
95 ptw32_mcs_lock_acquire(&ptw32_cond_list_lock, &node);
96
97 cv = ptw32_cond_list_head;
98
99 while (cv != NULL && 0 == result)
100 {
101 result = pthread_cond_broadcast (&cv);
102 cv = cv->next;
103 }
104
105 ptw32_mcs_lock_release(&node);
106
107 return (void *) (size_t) (result != 0 ? EAGAIN : 0);
108 }
109