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Change-Id: If3fad318bc2d620fa940de3f9595ff61024939df
This commit is contained in:
Michael Sevakis 2014-08-05 21:00:10 -04:00
parent 533d396761
commit bb7700928a
2 changed files with 397 additions and 0 deletions
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54
firmware/kernel/include/mrsw_lock.h Normal file
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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2014 by Michael Sevakis
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#ifndef MRSW_LOCK_H
#define MRSW_LOCK_H
/* Multi-reader, single-writer object that allows mutltiple readers or a
* single writer thread access to a critical section.
*
* Readers and writers, as with a mutex, may claim the lock recursively for
* the same type of access they were already granted.
*
* Writers are trivially granted read access by ignoring the request; the
* object is not changed.
*
* Reader promotion to writer is NOT supported and a reader attempting write
* access will result in a deadlock. That could change but for now, be warned.
*
* Full priority inheritance is implemented.
*/
struct mrsw_lock
{
int volatile count; /* rd/wr counter; >0 = reader(s), <0 = writer */
struct thread_entry *queue;
struct blocker_splay splay; /* priority inheritance info
for waiters */
uint8_t rdrecursion[MAXTHREADS]; /* per-thread reader recursion counts */
IF_COP( struct corelock cl; )
};
void mrsw_init(struct mrsw_lock *mrsw);
void mrsw_read_acquire(struct mrsw_lock *mrsw);
void mrsw_read_release(struct mrsw_lock *mrsw);
void mrsw_write_acquire(struct mrsw_lock *mrsw);
void mrsw_write_release(struct mrsw_lock *mrsw);
#endif /* MRSW_LOCK_H */