54 lines
1.3 KiB
C
54 lines
1.3 KiB
C
/*
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* \brief Spin lock implementation
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* \author Norman Feske
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* \author Stefan Kalkowski
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* \date 2009-03-25
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*/
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/*
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* Copyright (C) 2009-2013 Genode Labs GmbH
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*
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* This file is part of the Genode OS framework, which is distributed
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* under the terms of the GNU General Public License version 2.
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*/
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#ifndef _INCLUDE__BASE__INTERNAL__SPIN_LOCK_H_
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#define _INCLUDE__BASE__INTERNAL__SPIN_LOCK_H_
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/* Genode includes */
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#include <cpu/atomic.h>
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#include <cpu/memory_barrier.h>
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/* base-internal includes */
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#include <base/internal/lock_helper.h>
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/*
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* Spinlock functions used for protecting the critical sections within the
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* 'lock' and 'unlock' functions. Contention in these short-running code
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* portions is rare but is must be considered.
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*/
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enum State { SPINLOCK_LOCKED, SPINLOCK_UNLOCKED };
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static inline void spinlock_lock(volatile int *lock_variable)
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{
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while (!Genode::cmpxchg(lock_variable, SPINLOCK_UNLOCKED, SPINLOCK_LOCKED)) {
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/*
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* Yield our remaining time slice to help the spinlock holder to pass
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* the critical section.
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*/
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thread_yield();
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}
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}
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static inline void spinlock_unlock(volatile int *lock_variable)
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{
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/* make sure all got written by compiler before releasing lock */
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Genode::memory_barrier();
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*lock_variable = SPINLOCK_UNLOCKED;
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}
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#endif /* _INCLUDE__BASE__INTERNAL__SPIN_LOCK_H_ */
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