78 lines
2.8 KiB
C
78 lines
2.8 KiB
C
/*
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* This file is part of the SPL: Solaris Porting Layer.
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*
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* Copyright (c) 2009 Lawrence Livermore National Security, LLC.
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* Produced at Lawrence Livermore National Laboratory
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* Written by:
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* Brian Behlendorf <behlendorf1@llnl.gov>,
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* Herb Wartens <wartens2@llnl.gov>,
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* Jim Garlick <garlick@llnl.gov>
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* UCRL-CODE-235197
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*
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* This is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <sys/mutex.h>
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#ifdef DEBUG_SUBSYSTEM
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#undef DEBUG_SUBSYSTEM
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#endif
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#define DEBUG_SUBSYSTEM S_MUTEX
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/*
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* While a standard mutex implementation has been available in the kernel
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* for quite some time. It was not until 2.6.29 and latter kernels that
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* adaptive mutexs were embraced and integrated with the scheduler. This
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* brought a significant performance improvement, but just as importantly
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* it added a lock owner to the generic mutex outside CONFIG_DEBUG_MUTEXES
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* builds. This is critical for correctly supporting the mutex_owner()
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* Solaris primitive. When the owner is available we use a pure Linux
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* mutex implementation. When the owner is not available we still use
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* Linux mutexs as a base but also reserve space for an owner field right
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* after the mutex structure.
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*
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* In the case when HAVE_MUTEX_OWNER is not defined your code may
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* still me able to leverage adaptive mutexs. As long as the task_curr()
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* symbol is exported this code will provide a poor mans adaptive mutex
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* implementation. However, this is not required and if the symbol is
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* unavailable we provide a standard mutex.
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*/
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#ifndef HAVE_MUTEX_OWNER
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#ifdef HAVE_TASK_CURR
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/*
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* mutex_spin_max = { 0, -1, 1-MAX_INT }
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* 0: Never spin when trying to acquire lock
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* -1: Spin until acquired or holder yields without dropping lock
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* 1-MAX_INT: Spin for N attempts before sleeping for lock
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*/
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int mutex_spin_max = 0;
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module_param(mutex_spin_max, int, 0644);
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MODULE_PARM_DESC(mutex_spin_max, "Spin a maximum of N times to acquire lock");
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int
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spl_mutex_spin_max(void)
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{
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return mutex_spin_max;
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}
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EXPORT_SYMBOL(spl_mutex_spin_max);
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#endif /* HAVE_TASK_CURR */
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#endif /* !HAVE_MUTEX_OWNER */
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int spl_mutex_init(void) { return 0; }
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void spl_mutex_fini(void) { }
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