2 * lwpSem.c -- lwpSemaphore manipulation.
3 * Copyright (C) 1991-3 Stephen Crane.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Library General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Library General Public License for more details.
15 * You should have received a copy of the GNU Library General Public
16 * License along with this library; if not, write to the Free
17 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
19 * author: Stephen Crane, (jsc@doc.ic.ac.uk), Department of Computing,
20 * Imperial College of Science, Technology and Medicine, 180 Queen's
21 * Gate, London SW7 2BZ, England.
28 #include "prototypes.h"
30 #if defined(_EMPTH_LWP)
32 /* for systems without strdup */
34 extern char *strdup();
38 * create a lwpSemaphore.
40 struct lwpSem *lwpCreateSem(name, count)
46 if (!(new = (struct lwpSem *)malloc(sizeof(struct lwpSem))))
48 new->name = strdup(name);
50 new->q.head = new->q.tail = 0;
55 * signal a lwpSemaphore. We only yield here if
56 * the blocked process has a higher priority than ours'.
61 extern struct lwpProc *LwpCurrent;
63 lwpStatus(LwpCurrent, "done with semaphore %s", s->name);
65 struct lwpProc *p = lwpGetFirst(&s->q);
66 lwpStatus(LwpCurrent, "activating first waiter");
68 if (LwpCurrent->pri < p->pri) {
69 lwpStatus(p, "priority is higher");
76 * wait on a lwpSemaphore
81 extern struct lwpProc *LwpCurrent;
83 lwpStatus(LwpCurrent, "checking semaphore %s", s->name);
85 lwpStatus(LwpCurrent, "blocking");
86 lwpAddTail(&s->q, LwpCurrent);