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eb7721f2 | 1 | /* Copyright (C) 2003, 2007 Free Software Foundation, Inc. |
a88c9263 UD |
2 | This file is part of the GNU C Library. |
3 | Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C 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 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, write to the Free | |
17 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
18 | 02111-1307 USA. */ | |
19 | ||
20 | #include <errno.h> | |
21 | #include <sysdep.h> | |
22 | #include <lowlevellock.h> | |
23 | #include <pthread.h> | |
24 | #include <pthreadP.h> | |
25 | ||
26 | ||
27 | /* Acquire write lock for RWLOCK. */ | |
28 | int | |
29 | __pthread_rwlock_wrlock (rwlock) | |
30 | pthread_rwlock_t *rwlock; | |
31 | { | |
32 | int result = 0; | |
33 | ||
34 | /* Make sure we are along. */ | |
35 | lll_mutex_lock (rwlock->__data.__lock); | |
36 | ||
37 | while (1) | |
38 | { | |
39 | /* Get the rwlock if there is no writer and no reader. */ | |
b80770b2 | 40 | if (rwlock->__data.__writer == 0 && rwlock->__data.__nr_readers == 0) |
a88c9263 UD |
41 | { |
42 | /* Mark self as writer. */ | |
4ad0bbf4 | 43 | rwlock->__data.__writer = THREAD_GETMEM (THREAD_SELF, tid); |
a88c9263 UD |
44 | break; |
45 | } | |
46 | ||
47 | /* Make sure we are not holding the rwlock as a writer. This is | |
48 | a deadlock situation we recognize and report. */ | |
4ad0bbf4 UD |
49 | if (__builtin_expect (rwlock->__data.__writer |
50 | == THREAD_GETMEM (THREAD_SELF, tid), 0)) | |
a88c9263 UD |
51 | { |
52 | result = EDEADLK; | |
53 | break; | |
54 | } | |
55 | ||
56 | /* Remember that we are a writer. */ | |
57 | if (++rwlock->__data.__nr_writers_queued == 0) | |
58 | { | |
59 | /* Overflow on number of queued writers. */ | |
60 | --rwlock->__data.__nr_writers_queued; | |
61 | result = EAGAIN; | |
62 | break; | |
63 | } | |
64 | ||
18a53579 UD |
65 | int waitval = rwlock->__data.__writer_wakeup; |
66 | ||
a88c9263 UD |
67 | /* Free the lock. */ |
68 | lll_mutex_unlock (rwlock->__data.__lock); | |
69 | ||
70 | /* Wait for the writer or reader(s) to finish. */ | |
eb7721f2 UD |
71 | lll_futex_wait (&rwlock->__data.__writer_wakeup, waitval, |
72 | // XYZ check mutex flag | |
73 | LLL_SHARED); | |
a88c9263 UD |
74 | |
75 | /* Get the lock. */ | |
76 | lll_mutex_lock (rwlock->__data.__lock); | |
77 | ||
78 | /* To start over again, remove the thread from the writer list. */ | |
79 | --rwlock->__data.__nr_writers_queued; | |
a88c9263 UD |
80 | } |
81 | ||
82 | /* We are done, free the lock. */ | |
83 | lll_mutex_unlock (rwlock->__data.__lock); | |
84 | ||
85 | return result; | |
86 | } | |
87 | ||
88 | weak_alias (__pthread_rwlock_wrlock, pthread_rwlock_wrlock) | |
89 | strong_alias (__pthread_rwlock_wrlock, __pthread_rwlock_wrlock_internal) |