From bb7700928a05c42339be4f587b105659bc8dc2be Mon Sep 17 00:00:00 2001 From: Michael Sevakis Date: Tue, 5 Aug 2014 21:00:10 -0400 Subject: Oops. Somehow lost the track of the new files last push. Change-Id: If3fad318bc2d620fa940de3f9595ff61024939df --- firmware/kernel/include/mrsw_lock.h | 54 +++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 firmware/kernel/include/mrsw_lock.h (limited to 'firmware/kernel/include/mrsw_lock.h') 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 @@ +/*************************************************************************** + * __________ __ ___. + * 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 */ -- cgit v1.2.3