1*062c5bc4SJason Schmidlapp /*
2*062c5bc4SJason Schmidlapp * pthread_cond_signal.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 * Algorithm:
45*062c5bc4SJason Schmidlapp * See the comments at the top of pthread_cond_wait.c.
46*062c5bc4SJason Schmidlapp */
47*062c5bc4SJason Schmidlapp
48*062c5bc4SJason Schmidlapp #include "pthread.h"
49*062c5bc4SJason Schmidlapp #include "implement.h"
50*062c5bc4SJason Schmidlapp
51*062c5bc4SJason Schmidlapp static int
pte_cond_unblock(pthread_cond_t * cond,int unblockAll)52*062c5bc4SJason Schmidlapp pte_cond_unblock (pthread_cond_t * cond, int unblockAll)
53*062c5bc4SJason Schmidlapp /*
54*062c5bc4SJason Schmidlapp * Notes.
55*062c5bc4SJason Schmidlapp *
56*062c5bc4SJason Schmidlapp * Does not use the external mutex for synchronisation,
57*062c5bc4SJason Schmidlapp * therefore semBlockLock is needed.
58*062c5bc4SJason Schmidlapp * mtxUnblockLock is for LEVEL-2 synch. LEVEL-2 is the
59*062c5bc4SJason Schmidlapp * state where the external mutex is not necessarily locked by
60*062c5bc4SJason Schmidlapp * any thread, ie. between cond_wait unlocking and re-acquiring
61*062c5bc4SJason Schmidlapp * the lock after having been signaled or a timeout or
62*062c5bc4SJason Schmidlapp * cancellation.
63*062c5bc4SJason Schmidlapp *
64*062c5bc4SJason Schmidlapp * Uses the following CV elements:
65*062c5bc4SJason Schmidlapp * nWaitersBlocked
66*062c5bc4SJason Schmidlapp * nWaitersToUnblock
67*062c5bc4SJason Schmidlapp * nWaitersGone
68*062c5bc4SJason Schmidlapp * mtxUnblockLock
69*062c5bc4SJason Schmidlapp * semBlockLock
70*062c5bc4SJason Schmidlapp * semBlockQueue
71*062c5bc4SJason Schmidlapp */
72*062c5bc4SJason Schmidlapp {
73*062c5bc4SJason Schmidlapp int result;
74*062c5bc4SJason Schmidlapp pthread_cond_t cv;
75*062c5bc4SJason Schmidlapp int nSignalsToIssue;
76*062c5bc4SJason Schmidlapp
77*062c5bc4SJason Schmidlapp if (cond == NULL || *cond == NULL)
78*062c5bc4SJason Schmidlapp {
79*062c5bc4SJason Schmidlapp return EINVAL;
80*062c5bc4SJason Schmidlapp }
81*062c5bc4SJason Schmidlapp
82*062c5bc4SJason Schmidlapp cv = *cond;
83*062c5bc4SJason Schmidlapp
84*062c5bc4SJason Schmidlapp /*
85*062c5bc4SJason Schmidlapp * No-op if the CV is static and hasn't been initialised yet.
86*062c5bc4SJason Schmidlapp * Assuming that any race condition is harmless.
87*062c5bc4SJason Schmidlapp */
88*062c5bc4SJason Schmidlapp if (cv == PTHREAD_COND_INITIALIZER)
89*062c5bc4SJason Schmidlapp {
90*062c5bc4SJason Schmidlapp return 0;
91*062c5bc4SJason Schmidlapp }
92*062c5bc4SJason Schmidlapp
93*062c5bc4SJason Schmidlapp if ((result = pthread_mutex_lock (&(cv->mtxUnblockLock))) != 0)
94*062c5bc4SJason Schmidlapp {
95*062c5bc4SJason Schmidlapp return result;
96*062c5bc4SJason Schmidlapp }
97*062c5bc4SJason Schmidlapp
98*062c5bc4SJason Schmidlapp if (0 != cv->nWaitersToUnblock)
99*062c5bc4SJason Schmidlapp {
100*062c5bc4SJason Schmidlapp if (0 == cv->nWaitersBlocked)
101*062c5bc4SJason Schmidlapp {
102*062c5bc4SJason Schmidlapp return pthread_mutex_unlock (&(cv->mtxUnblockLock));
103*062c5bc4SJason Schmidlapp }
104*062c5bc4SJason Schmidlapp if (unblockAll)
105*062c5bc4SJason Schmidlapp {
106*062c5bc4SJason Schmidlapp cv->nWaitersToUnblock += (nSignalsToIssue = cv->nWaitersBlocked);
107*062c5bc4SJason Schmidlapp cv->nWaitersBlocked = 0;
108*062c5bc4SJason Schmidlapp }
109*062c5bc4SJason Schmidlapp else
110*062c5bc4SJason Schmidlapp {
111*062c5bc4SJason Schmidlapp nSignalsToIssue = 1;
112*062c5bc4SJason Schmidlapp cv->nWaitersToUnblock++;
113*062c5bc4SJason Schmidlapp cv->nWaitersBlocked--;
114*062c5bc4SJason Schmidlapp }
115*062c5bc4SJason Schmidlapp }
116*062c5bc4SJason Schmidlapp else if (cv->nWaitersBlocked > cv->nWaitersGone)
117*062c5bc4SJason Schmidlapp {
118*062c5bc4SJason Schmidlapp /* Use the non-cancellable version of sem_wait() */
119*062c5bc4SJason Schmidlapp // if (sem_wait_nocancel (&(cv->semBlockLock)) != 0)
120*062c5bc4SJason Schmidlapp if (sem_wait (&(cv->semBlockLock)) != 0)
121*062c5bc4SJason Schmidlapp {
122*062c5bc4SJason Schmidlapp result = errno;
123*062c5bc4SJason Schmidlapp (void) pthread_mutex_unlock (&(cv->mtxUnblockLock));
124*062c5bc4SJason Schmidlapp return result;
125*062c5bc4SJason Schmidlapp }
126*062c5bc4SJason Schmidlapp if (0 != cv->nWaitersGone)
127*062c5bc4SJason Schmidlapp {
128*062c5bc4SJason Schmidlapp cv->nWaitersBlocked -= cv->nWaitersGone;
129*062c5bc4SJason Schmidlapp cv->nWaitersGone = 0;
130*062c5bc4SJason Schmidlapp }
131*062c5bc4SJason Schmidlapp if (unblockAll)
132*062c5bc4SJason Schmidlapp {
133*062c5bc4SJason Schmidlapp nSignalsToIssue = cv->nWaitersToUnblock = cv->nWaitersBlocked;
134*062c5bc4SJason Schmidlapp cv->nWaitersBlocked = 0;
135*062c5bc4SJason Schmidlapp }
136*062c5bc4SJason Schmidlapp else
137*062c5bc4SJason Schmidlapp {
138*062c5bc4SJason Schmidlapp nSignalsToIssue = cv->nWaitersToUnblock = 1;
139*062c5bc4SJason Schmidlapp cv->nWaitersBlocked--;
140*062c5bc4SJason Schmidlapp }
141*062c5bc4SJason Schmidlapp }
142*062c5bc4SJason Schmidlapp else
143*062c5bc4SJason Schmidlapp {
144*062c5bc4SJason Schmidlapp return pthread_mutex_unlock (&(cv->mtxUnblockLock));
145*062c5bc4SJason Schmidlapp }
146*062c5bc4SJason Schmidlapp
147*062c5bc4SJason Schmidlapp if ((result = pthread_mutex_unlock (&(cv->mtxUnblockLock))) == 0)
148*062c5bc4SJason Schmidlapp {
149*062c5bc4SJason Schmidlapp if (sem_post_multiple (&(cv->semBlockQueue), nSignalsToIssue) != 0)
150*062c5bc4SJason Schmidlapp {
151*062c5bc4SJason Schmidlapp result = errno;
152*062c5bc4SJason Schmidlapp }
153*062c5bc4SJason Schmidlapp }
154*062c5bc4SJason Schmidlapp
155*062c5bc4SJason Schmidlapp return result;
156*062c5bc4SJason Schmidlapp
157*062c5bc4SJason Schmidlapp } /* pte_cond_unblock */
158*062c5bc4SJason Schmidlapp
159*062c5bc4SJason Schmidlapp int
pthread_cond_signal(pthread_cond_t * cond)160*062c5bc4SJason Schmidlapp pthread_cond_signal (pthread_cond_t * cond)
161*062c5bc4SJason Schmidlapp /*
162*062c5bc4SJason Schmidlapp * ------------------------------------------------------
163*062c5bc4SJason Schmidlapp * DOCPUBLIC
164*062c5bc4SJason Schmidlapp * This function signals a condition variable, waking
165*062c5bc4SJason Schmidlapp * one waiting thread.
166*062c5bc4SJason Schmidlapp * If SCHED_FIFO or SCHED_RR policy threads are waiting
167*062c5bc4SJason Schmidlapp * the highest priority waiter is awakened; otherwise,
168*062c5bc4SJason Schmidlapp * an unspecified waiter is awakened.
169*062c5bc4SJason Schmidlapp *
170*062c5bc4SJason Schmidlapp * PARAMETERS
171*062c5bc4SJason Schmidlapp * cond
172*062c5bc4SJason Schmidlapp * pointer to an instance of pthread_cond_t
173*062c5bc4SJason Schmidlapp *
174*062c5bc4SJason Schmidlapp *
175*062c5bc4SJason Schmidlapp * DESCRIPTION
176*062c5bc4SJason Schmidlapp * This function signals a condition variable, waking
177*062c5bc4SJason Schmidlapp * one waiting thread.
178*062c5bc4SJason Schmidlapp * If SCHED_FIFO or SCHED_RR policy threads are waiting
179*062c5bc4SJason Schmidlapp * the highest priority waiter is awakened; otherwise,
180*062c5bc4SJason Schmidlapp * an unspecified waiter is awakened.
181*062c5bc4SJason Schmidlapp *
182*062c5bc4SJason Schmidlapp * NOTES:
183*062c5bc4SJason Schmidlapp *
184*062c5bc4SJason Schmidlapp * 1) Use when any waiter can respond and only one need
185*062c5bc4SJason Schmidlapp * respond (all waiters being equal).
186*062c5bc4SJason Schmidlapp *
187*062c5bc4SJason Schmidlapp * RESULTS
188*062c5bc4SJason Schmidlapp * 0 successfully signaled condition,
189*062c5bc4SJason Schmidlapp * EINVAL 'cond' is invalid,
190*062c5bc4SJason Schmidlapp *
191*062c5bc4SJason Schmidlapp * ------------------------------------------------------
192*062c5bc4SJason Schmidlapp */
193*062c5bc4SJason Schmidlapp {
194*062c5bc4SJason Schmidlapp /*
195*062c5bc4SJason Schmidlapp * The '0'(FALSE) unblockAll arg means unblock ONE waiter.
196*062c5bc4SJason Schmidlapp */
197*062c5bc4SJason Schmidlapp return (pte_cond_unblock (cond, 0));
198*062c5bc4SJason Schmidlapp
199*062c5bc4SJason Schmidlapp } /* pthread_cond_signal */
200*062c5bc4SJason Schmidlapp
201*062c5bc4SJason Schmidlapp int
pthread_cond_broadcast(pthread_cond_t * cond)202*062c5bc4SJason Schmidlapp pthread_cond_broadcast (pthread_cond_t * cond)
203*062c5bc4SJason Schmidlapp /*
204*062c5bc4SJason Schmidlapp * ------------------------------------------------------
205*062c5bc4SJason Schmidlapp * DOCPUBLIC
206*062c5bc4SJason Schmidlapp * This function broadcasts the condition variable,
207*062c5bc4SJason Schmidlapp * waking all current waiters.
208*062c5bc4SJason Schmidlapp *
209*062c5bc4SJason Schmidlapp * PARAMETERS
210*062c5bc4SJason Schmidlapp * cond
211*062c5bc4SJason Schmidlapp * pointer to an instance of pthread_cond_t
212*062c5bc4SJason Schmidlapp *
213*062c5bc4SJason Schmidlapp *
214*062c5bc4SJason Schmidlapp * DESCRIPTION
215*062c5bc4SJason Schmidlapp * This function signals a condition variable, waking
216*062c5bc4SJason Schmidlapp * all waiting threads.
217*062c5bc4SJason Schmidlapp *
218*062c5bc4SJason Schmidlapp * NOTES:
219*062c5bc4SJason Schmidlapp *
220*062c5bc4SJason Schmidlapp * 1) Use when more than one waiter may respond to
221*062c5bc4SJason Schmidlapp * predicate change or if any waiting thread may
222*062c5bc4SJason Schmidlapp * not be able to respond
223*062c5bc4SJason Schmidlapp *
224*062c5bc4SJason Schmidlapp * RESULTS
225*062c5bc4SJason Schmidlapp * 0 successfully signalled condition to all
226*062c5bc4SJason Schmidlapp * waiting threads,
227*062c5bc4SJason Schmidlapp * EINVAL 'cond' is invalid
228*062c5bc4SJason Schmidlapp * ENOSPC a required resource has been exhausted,
229*062c5bc4SJason Schmidlapp *
230*062c5bc4SJason Schmidlapp * ------------------------------------------------------
231*062c5bc4SJason Schmidlapp */
232*062c5bc4SJason Schmidlapp {
233*062c5bc4SJason Schmidlapp /*
234*062c5bc4SJason Schmidlapp * The TRUE unblockAll arg means unblock ALL waiters.
235*062c5bc4SJason Schmidlapp */
236*062c5bc4SJason Schmidlapp return (pte_cond_unblock (cond, PTE_TRUE));
237*062c5bc4SJason Schmidlapp
238*062c5bc4SJason Schmidlapp } /* pthread_cond_broadcast */
239