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/*****************************************************************************\
* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
* Copyright (C) 2007 The Regents of the University of California.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
* For details, see <http://github.com/behlendorf/spl/>.
*
* The SPL 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.
*
* The SPL is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
*****************************************************************************
* Solaris Porting Layer (SPL) Mutex Implementation.
\*****************************************************************************/
#include <sys/mutex.h>
#ifdef DEBUG_SUBSYSTEM
#undef DEBUG_SUBSYSTEM
#endif
#define DEBUG_SUBSYSTEM S_MUTEX
/*
* While a standard mutex implementation has been available in the kernel
* for quite some time. It was not until 2.6.29 and latter kernels that
* adaptive mutexs were embraced and integrated with the scheduler. This
* brought a significant performance improvement, but just as importantly
* it added a lock owner to the generic mutex outside CONFIG_DEBUG_MUTEXES
* builds. This is critical for correctly supporting the mutex_owner()
* Solaris primitive. When the owner is available we use a pure Linux
* mutex implementation. When the owner is not available we still use
* Linux mutexs as a base but also reserve space for an owner field right
* after the mutex structure.
*
* In the case when HAVE_MUTEX_OWNER is not defined your code may
* still me able to leverage adaptive mutexs. As long as the task_curr()
* symbol is exported this code will provide a poor mans adaptive mutex
* implementation. However, this is not required and if the symbol is
* unavailable we provide a standard mutex.
*/
#if !defined(HAVE_MUTEX_OWNER) || !defined(CONFIG_SMP) || defined(CONFIG_DEBUG_MUTEXES)
#ifdef HAVE_TASK_CURR
/*
* mutex_spin_max = { 0, -1, 1-MAX_INT }
* 0: Never spin when trying to acquire lock
* -1: Spin until acquired or holder yields without dropping lock
* 1-MAX_INT: Spin for N attempts before sleeping for lock
*/
int mutex_spin_max = 0;
module_param(mutex_spin_max, int, 0644);
MODULE_PARM_DESC(mutex_spin_max, "Spin a maximum of N times to acquire lock");
int
spl_mutex_spin_max(void)
{
return mutex_spin_max;
}
EXPORT_SYMBOL(spl_mutex_spin_max);
#endif /* HAVE_TASK_CURR */
#endif /* !HAVE_MUTEX_OWNER */
int spl_mutex_init(void) { return 0; }
void spl_mutex_fini(void) { }
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