diff options
Diffstat (limited to 'firmware/kernel/include')
-rw-r--r-- | firmware/kernel/include/mrsw_lock.h | 54 |
1 files changed, 54 insertions, 0 deletions
diff --git a/firmware/kernel/include/mrsw_lock.h b/firmware/kernel/include/mrsw_lock.h new file mode 100644 index 0000000000..fbfe1d405d --- /dev/null +++ b/firmware/kernel/include/mrsw_lock.h | |||
@@ -0,0 +1,54 @@ | |||
1 | /*************************************************************************** | ||
2 | * __________ __ ___. | ||
3 | * Open \______ \ ____ ____ | | _\_ |__ _______ ___ | ||
4 | * Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ / | ||
5 | * Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < < | ||
6 | * Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \ | ||
7 | * \/ \/ \/ \/ \/ | ||
8 | * $Id$ | ||
9 | * | ||
10 | * Copyright (C) 2014 by Michael Sevakis | ||
11 | * | ||
12 | * This program is free software; you can redistribute it and/or | ||
13 | * modify it under the terms of the GNU General Public License | ||
14 | * as published by the Free Software Foundation; either version 2 | ||
15 | * of the License, or (at your option) any later version. | ||
16 | * | ||
17 | * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY | ||
18 | * KIND, either express or implied. | ||
19 | * | ||
20 | ****************************************************************************/ | ||
21 | #ifndef MRSW_LOCK_H | ||
22 | #define MRSW_LOCK_H | ||
23 | |||
24 | /* Multi-reader, single-writer object that allows mutltiple readers or a | ||
25 | * single writer thread access to a critical section. | ||
26 | * | ||
27 | * Readers and writers, as with a mutex, may claim the lock recursively for | ||
28 | * the same type of access they were already granted. | ||
29 | * | ||
30 | * Writers are trivially granted read access by ignoring the request; the | ||
31 | * object is not changed. | ||
32 | * | ||
33 | * Reader promotion to writer is NOT supported and a reader attempting write | ||
34 | * access will result in a deadlock. That could change but for now, be warned. | ||
35 | * | ||
36 | * Full priority inheritance is implemented. | ||
37 | */ | ||
38 | struct mrsw_lock | ||
39 | { | ||
40 | int volatile count; /* rd/wr counter; >0 = reader(s), <0 = writer */ | ||
41 | struct thread_entry *queue; | ||
42 | struct blocker_splay splay; /* priority inheritance info | ||
43 | for waiters */ | ||
44 | uint8_t rdrecursion[MAXTHREADS]; /* per-thread reader recursion counts */ | ||
45 | IF_COP( struct corelock cl; ) | ||
46 | }; | ||
47 | |||
48 | void mrsw_init(struct mrsw_lock *mrsw); | ||
49 | void mrsw_read_acquire(struct mrsw_lock *mrsw); | ||
50 | void mrsw_read_release(struct mrsw_lock *mrsw); | ||
51 | void mrsw_write_acquire(struct mrsw_lock *mrsw); | ||
52 | void mrsw_write_release(struct mrsw_lock *mrsw); | ||
53 | |||
54 | #endif /* MRSW_LOCK_H */ | ||