126 lines
3.8 KiB
C
126 lines
3.8 KiB
C
/* Copyright (c) 2008-2009, 2011, 2013 The Linux Foundation.
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 and
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* only version 2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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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 <linux/spinlock.h>
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#include <linux/mutex.h>
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#include <asm/remote_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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#define remote_spin_trylock(lock) \
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({ \
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spin_trylock(&((lock)->local)) \
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? _remote_spin_trylock(&((lock)->remote)) \
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? 1 \
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: ({ spin_unlock(&((lock)->local)); 0; }) \
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: 0; \
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})
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#define remote_spin_trylock_irqsave(lock, flags) \
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({ \
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spin_trylock_irqsave(&((lock)->local), flags) \
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? _remote_spin_trylock(&((lock)->remote)) \
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? 1 \
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: ({ spin_unlock_irqrestore(&((lock)->local), flags); \
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0; }) \
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: 0; \
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})
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#define remote_spin_release(lock, pid) \
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_remote_spin_release(&((lock)->remote), pid)
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#define remote_spin_release_all(pid) \
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_remote_spin_release_all(pid)
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#define remote_spin_owner(lock) \
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_remote_spin_owner(&((lock)->remote))
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typedef struct {
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struct mutex local;
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_remote_mutex_t remote;
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} remote_mutex_t;
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#define remote_mutex_init(lock, id) \
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({ \
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mutex_init(&((lock)->local)); \
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_remote_mutex_init(id, &((lock)->remote)); \
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})
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#define remote_mutex_lock(lock) \
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do { \
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mutex_lock(&((lock)->local)); \
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_remote_mutex_lock(&((lock)->remote)); \
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} while (0)
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#define remote_mutex_trylock(lock) \
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({ \
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mutex_trylock(&((lock)->local)) \
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? _remote_mutex_trylock(&((lock)->remote)) \
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? 1 \
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: ({mutex_unlock(&((lock)->local)); 0; }) \
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: 0; \
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})
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#define remote_mutex_unlock(lock) \
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do { \
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_remote_mutex_unlock(&((lock)->remote)); \
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mutex_unlock(&((lock)->local)); \
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} while (0)
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#endif
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