1 /*****************************************************************************\
2 * Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
3 * Copyright (C) 2007 The Regents of the University of California.
4 * Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
5 * Written by Brian Behlendorf <behlendorf1@llnl.gov>.
8 * This file is part of the SPL, Solaris Porting Layer.
9 * For details, see <http://zfsonlinux.org/>.
11 * The SPL is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU General Public License as published by the
13 * Free Software Foundation; either version 2 of the License, or (at your
14 * option) any later version.
16 * The SPL is distributed in the hope that it will be useful, but WITHOUT
17 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
18 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
21 * You should have received a copy of the GNU General Public License along
22 * with the SPL. If not, see <http://www.gnu.org/licenses/>.
23 *****************************************************************************
24 * Solaris Porting Layer (SPL) Reader/Writer Lock Implementation.
25 \*****************************************************************************/
27 #include <sys/rwlock.h>
29 #ifdef DEBUG_SUBSYSTEM
30 #undef DEBUG_SUBSYSTEM
33 #define DEBUG_SUBSYSTEM S_RWLOCK
35 #if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
37 __rwsem_tryupgrade(struct rw_semaphore
*rwsem
)
41 spl_rwsem_lock_irqsave(&rwsem
->wait_lock
, flags
);
42 if (RWSEM_COUNT(rwsem
) == SPL_RWSEM_SINGLE_READER_VALUE
&&
43 list_empty(&rwsem
->wait_list
)) {
45 RWSEM_COUNT(rwsem
) = SPL_RWSEM_SINGLE_WRITER_VALUE
;
47 spl_rwsem_unlock_irqrestore(&rwsem
->wait_lock
, flags
);
50 #elif defined(HAVE_RWSEM_ATOMIC_LONG_COUNT)
52 __rwsem_tryupgrade(struct rw_semaphore
*rwsem
)
55 val
= atomic_long_cmpxchg(&rwsem
->count
, SPL_RWSEM_SINGLE_READER_VALUE
,
56 SPL_RWSEM_SINGLE_WRITER_VALUE
);
57 return (val
== SPL_RWSEM_SINGLE_READER_VALUE
);
61 __rwsem_tryupgrade(struct rw_semaphore
*rwsem
)
63 typeof (rwsem
->count
) val
;
64 val
= cmpxchg(&rwsem
->count
, SPL_RWSEM_SINGLE_READER_VALUE
,
65 SPL_RWSEM_SINGLE_WRITER_VALUE
);
66 return (val
== SPL_RWSEM_SINGLE_READER_VALUE
);
71 rwsem_tryupgrade(struct rw_semaphore
*rwsem
)
73 if (__rwsem_tryupgrade(rwsem
)) {
74 rwsem_release(&rwsem
->dep_map
, 1, _RET_IP_
);
75 rwsem_acquire(&rwsem
->dep_map
, 0, 1, _RET_IP_
);
76 #ifdef CONFIG_RWSEM_SPIN_ON_OWNER
77 rwsem
->owner
= current
;
83 EXPORT_SYMBOL(rwsem_tryupgrade
);
85 int spl_rw_init(void) { return 0; }
86 void spl_rw_fini(void) { }