1 | /* Copyright (C) 2003-2016 Free Software Foundation, Inc. |
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, see |
17 | <http://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <errno.h> |
20 | #include <sysdep.h> |
21 | #include <lowlevellock.h> |
22 | #include <futex-internal.h> |
23 | #include <pthread.h> |
24 | #include <pthreadP.h> |
25 | #include <stap-probe.h> |
26 | #include <elide.h> |
27 | |
28 | |
29 | /* Unlock RWLOCK. */ |
30 | int |
31 | __pthread_rwlock_unlock (pthread_rwlock_t *rwlock) |
32 | { |
33 | int futex_shared = |
34 | rwlock->__data.__shared == LLL_PRIVATE ? FUTEX_PRIVATE : FUTEX_SHARED; |
35 | |
36 | LIBC_PROBE (rwlock_unlock, 1, rwlock); |
37 | |
38 | if (ELIDE_UNLOCK (rwlock->__data.__writer == 0 |
39 | && rwlock->__data.__nr_readers == 0)) |
40 | return 0; |
41 | |
42 | lll_lock (rwlock->__data.__lock, rwlock->__data.__shared); |
43 | if (rwlock->__data.__writer) |
44 | rwlock->__data.__writer = 0; |
45 | else |
46 | --rwlock->__data.__nr_readers; |
47 | /* If there are still readers present, we do not yet need to wake writers |
48 | nor are responsible to wake any readers. */ |
49 | if (rwlock->__data.__nr_readers == 0) |
50 | { |
51 | /* Note that if there is a blocked writer, we effectively make it |
52 | responsible for waking any readers because we don't wake readers in |
53 | this case. */ |
54 | if (rwlock->__data.__nr_writers_queued) |
55 | { |
56 | ++rwlock->__data.__writer_wakeup; |
57 | lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); |
58 | futex_wake (&rwlock->__data.__writer_wakeup, 1, futex_shared); |
59 | return 0; |
60 | } |
61 | else if (rwlock->__data.__nr_readers_queued) |
62 | { |
63 | ++rwlock->__data.__readers_wakeup; |
64 | lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); |
65 | futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX, |
66 | futex_shared); |
67 | return 0; |
68 | } |
69 | } |
70 | lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared); |
71 | return 0; |
72 | } |
73 | |
74 | weak_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock) |
75 | hidden_def (__pthread_rwlock_unlock) |
76 | |