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2 * This file is part of the SPL: Solaris Porting Layer.
4 * Copyright (c) 2009 Lawrence Livermore National Security, LLC.
5 * Produced at Lawrence Livermore National Laboratory
7 * Brian Behlendorf <behlendorf1@llnl.gov>,
8 * Herb Wartens <wartens2@llnl.gov>,
9 * Jim Garlick <garlick@llnl.gov>
12 * This is free software; you can redistribute it and/or modify it
13 * under the terms of the GNU General Public License as published by
14 * the Free Software Foundation; either version 2 of the License, or
15 * (at your option) any later version.
17 * This is distributed in the hope that it will be useful, but WITHOUT
18 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
19 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
22 * You should have received a copy of the GNU General Public License along
23 * with this program; if not, write to the Free Software Foundation, Inc.,
24 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
27 #include <sys/mutex.h>
29 #ifdef DEBUG_SUBSYSTEM
30 #undef DEBUG_SUBSYSTEM
33 #define DEBUG_SUBSYSTEM S_MUTEX
36 * While a standard mutex implementation has been available in the kernel
37 * for quite some time. It was not until 2.6.29 and latter kernels that
38 * adaptive mutexs were embraced and integrated with the scheduler. This
39 * brought a significant performance improvement, but just as importantly
40 * it added a lock owner to the generic mutex outside CONFIG_DEBUG_MUTEXES
41 * builds. This is critical for correctly supporting the mutex_owner()
42 * Solaris primitive. When the owner is available we use a pure Linux
43 * mutex implementation. When the owner is not available we still use
44 * Linux mutexs as a base but also reserve space for an owner field right
45 * after the mutex structure.
47 * In the case when HAVE_MUTEX_OWNER is not defined your code may
48 * still me able to leverage adaptive mutexs. As long as the task_curr()
49 * symbol is exported this code will provide a poor mans adaptive mutex
50 * implementation. However, this is not required and if the symbol is
51 * unavailable we provide a standard mutex.
54 #ifndef HAVE_MUTEX_OWNER
57 * mutex_spin_max = { 0, -1, 1-MAX_INT }
58 * 0: Never spin when trying to acquire lock
59 * -1: Spin until acquired or holder yields without dropping lock
60 * 1-MAX_INT: Spin for N attempts before sleeping for lock
62 int mutex_spin_max
= 0;
63 module_param(mutex_spin_max
, int, 0644);
64 MODULE_PARM_DESC(mutex_spin_max
, "Spin a maximum of N times to acquire lock");
67 spl_mutex_spin_max(void)
69 return mutex_spin_max
;
71 EXPORT_SYMBOL(spl_mutex_spin_max
);
73 #endif /* HAVE_TASK_CURR */
74 #endif /* !HAVE_MUTEX_OWNER */
76 int spl_mutex_init(void) { return 0; }
77 void spl_mutex_fini(void) { }