1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
|
/* Copyright (C) 2008 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by David Bartley <dtbartle@csclub.uwaterloo.ca>, 2008.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <errno.h>
#include <pthreadP.h>
#include <synch.h>
int rw_unlock (rwlock)
rwlock_t *rwlock;
{
int errval = mutex_lock (&rwlock->mutex);
if (errval != 0)
return errval;
if (rwlock->readers & _RWLOCK_WR_LOCK)
{
/* Writer unlock. */
if (__builtin_expect (rwlock->owner != (uintptr_t)THREAD_SELF, 0) ||
((rwlock->type & LOCK_SHARED) && __builtin_expect (
rwlock->ownerpid != THREAD_GETMEM (THREAD_SELF, pid), 0)))
{
(void)mutex_unlock (&rwlock->mutex);
return EBUSY;
}
rwlock->owner = rwlock->ownerpid = 0;
rwlock->readers &= ~_RWLOCK_WR_LOCK;
}
else
{
/* Reader unlock. */
if ((rwlock->readers & _RWLOCK_RD_MASK) == 0)
{
(void)mutex_unlock (&rwlock->mutex);
return EBUSY;
}
rwlock->readers = (rwlock->readers & _RWLOCK_WR_LOCK) |
((rwlock->readers & _RWLOCK_RD_MASK) - 1);
}
/* Wake up a writer (if possible) or all readers. */
if ((rwlock->readers & _RWLOCK_RD_MASK) == 0 &&
__cond_has_waiters (&rwlock->writercv))
errval = cond_signal (&rwlock->writercv);
else if (__cond_has_waiters (&rwlock->readercv))
errval = cond_broadcast (&rwlock->readercv);
(void)mutex_unlock (&rwlock->mutex);
return errval;
}
|
