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 *      59 Temple Place - Suite 330, Boston, MA 02111-1307, 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
64void *
65pthread_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