83 lines
3.5 KiB
C
83 lines
3.5 KiB
C
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/* Copyright (c) 2008-2009, Code Aurora Forum. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of Code Aurora nor
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* the names of its contributors may be used to endorse or promote
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* products derived from this software without specific prior written
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* permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NON-INFRINGEMENT ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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* OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
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* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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#ifndef __LINUX_REMOTE_SPINLOCK_H
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#define __LINUX_REMOTE_SPINLOCK_H
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#include <mach/remote_spinlock.h>
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#include <linux/spinlock.h>
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/* Grabbing a local spin lock before going for a remote lock has several
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* advantages:
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* 1. Get calls to preempt enable/disable and IRQ save/restore for free.
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* 2. For UP kernel, there is no overhead.
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* 3. Reduces the possibility of executing the remote spin lock code. This is
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* especially useful when the remote CPUs' mutual exclusion instructions
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* don't work with the local CPUs' instructions. In such cases, one has to
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* use software based mutex algorithms (e.g. Lamport's bakery algorithm)
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* which could get expensive when the no. of contending CPUs is high.
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* 4. In the case of software based mutex algorithm the exection time will be
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* smaller since the no. of contending CPUs is reduced by having just one
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* contender for all the local CPUs.
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* 5. Get most of the spin lock debug features for free.
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* 6. The code will continue to work "gracefully" even when the remote spin
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* lock code is stubbed out for debug purposes or when there is no remote
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* CPU in some board/machine types.
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*/
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typedef struct {
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spinlock_t local;
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_remote_spinlock_t remote;
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} remote_spinlock_t;
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#define remote_spin_lock_init(lock, id) \
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({ \
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spin_lock_init(&((lock)->local)); \
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_remote_spin_lock_init(id, &((lock)->remote)); \
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})
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#define remote_spin_lock(lock) \
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do { \
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spin_lock(&((lock)->local)); \
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_remote_spin_lock(&((lock)->remote)); \
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} while (0)
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#define remote_spin_unlock(lock) \
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do { \
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_remote_spin_unlock(&((lock)->remote)); \
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spin_unlock(&((lock)->local)); \
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} while (0)
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#define remote_spin_lock_irqsave(lock, flags) \
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do { \
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spin_lock_irqsave(&((lock)->local), flags); \
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_remote_spin_lock(&((lock)->remote)); \
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} while (0)
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#define remote_spin_unlock_irqrestore(lock, flags) \
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do { \
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_remote_spin_unlock(&((lock)->remote)); \
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spin_unlock_irqrestore(&((lock)->local), flags); \
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} while (0)
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#endif
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