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9ea4c38006
Currently all _bh_ lock functions do two preempt_count operations:
local_bh_disable();
preempt_disable();
and for the unlock:
preempt_enable_no_resched();
local_bh_enable();
Since its a waste of perfectly good cycles to modify the same variable
twice when you can do it in one go; use the new
__local_bh_{dis,en}able_ip() functions that allow us to provide a
preempt_count value to add/sub.
So define SOFTIRQ_LOCK_OFFSET as the offset a _bh_ lock needs to
add/sub to be done in one go.
As a bonus it gets rid of the preempt_enable_no_resched() usage.
This reduces a 1000 loops of:
spin_lock_bh(&bh_lock);
spin_unlock_bh(&bh_lock);
from 53596 cycles to 51995 cycles. I didn't do enough measurements to
say for absolute sure that the result is significant but the the few
runs I did for each suggest it is so.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: jacob.jun.pan@linux.intel.com
Cc: Mike Galbraith <bitbucket@online.de>
Cc: hpa@zytor.com
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: lenb@kernel.org
Cc: rjw@rjwysocki.net
Cc: rui.zhang@intel.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
193 lines
5.4 KiB
C
193 lines
5.4 KiB
C
#ifndef __LINUX_SPINLOCK_API_SMP_H
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#define __LINUX_SPINLOCK_API_SMP_H
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#ifndef __LINUX_SPINLOCK_H
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# error "please don't include this file directly"
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#endif
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/*
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* include/linux/spinlock_api_smp.h
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*
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* spinlock API declarations on SMP (and debug)
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* (implemented in kernel/spinlock.c)
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*
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* portions Copyright 2005, Red Hat, Inc., Ingo Molnar
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* Released under the General Public License (GPL).
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*/
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int in_lock_functions(unsigned long addr);
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#define assert_raw_spin_locked(x) BUG_ON(!raw_spin_is_locked(x))
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void __lockfunc _raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
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void __lockfunc _raw_spin_lock_nested(raw_spinlock_t *lock, int subclass)
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__acquires(lock);
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void __lockfunc
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_raw_spin_lock_nest_lock(raw_spinlock_t *lock, struct lockdep_map *map)
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__acquires(lock);
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void __lockfunc _raw_spin_lock_bh(raw_spinlock_t *lock) __acquires(lock);
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void __lockfunc _raw_spin_lock_irq(raw_spinlock_t *lock)
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__acquires(lock);
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unsigned long __lockfunc _raw_spin_lock_irqsave(raw_spinlock_t *lock)
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__acquires(lock);
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unsigned long __lockfunc
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_raw_spin_lock_irqsave_nested(raw_spinlock_t *lock, int subclass)
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__acquires(lock);
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int __lockfunc _raw_spin_trylock(raw_spinlock_t *lock);
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int __lockfunc _raw_spin_trylock_bh(raw_spinlock_t *lock);
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void __lockfunc _raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
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void __lockfunc _raw_spin_unlock_bh(raw_spinlock_t *lock) __releases(lock);
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void __lockfunc _raw_spin_unlock_irq(raw_spinlock_t *lock) __releases(lock);
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void __lockfunc
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_raw_spin_unlock_irqrestore(raw_spinlock_t *lock, unsigned long flags)
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__releases(lock);
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#ifdef CONFIG_INLINE_SPIN_LOCK
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#define _raw_spin_lock(lock) __raw_spin_lock(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_LOCK_BH
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#define _raw_spin_lock_bh(lock) __raw_spin_lock_bh(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_LOCK_IRQ
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#define _raw_spin_lock_irq(lock) __raw_spin_lock_irq(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_LOCK_IRQSAVE
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#define _raw_spin_lock_irqsave(lock) __raw_spin_lock_irqsave(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_TRYLOCK
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#define _raw_spin_trylock(lock) __raw_spin_trylock(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_TRYLOCK_BH
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#define _raw_spin_trylock_bh(lock) __raw_spin_trylock_bh(lock)
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#endif
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#ifndef CONFIG_UNINLINE_SPIN_UNLOCK
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#define _raw_spin_unlock(lock) __raw_spin_unlock(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_UNLOCK_BH
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#define _raw_spin_unlock_bh(lock) __raw_spin_unlock_bh(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_UNLOCK_IRQ
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#define _raw_spin_unlock_irq(lock) __raw_spin_unlock_irq(lock)
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#endif
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#ifdef CONFIG_INLINE_SPIN_UNLOCK_IRQRESTORE
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#define _raw_spin_unlock_irqrestore(lock, flags) __raw_spin_unlock_irqrestore(lock, flags)
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#endif
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static inline int __raw_spin_trylock(raw_spinlock_t *lock)
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{
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preempt_disable();
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if (do_raw_spin_trylock(lock)) {
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spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
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return 1;
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}
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preempt_enable();
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return 0;
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}
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/*
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* If lockdep is enabled then we use the non-preemption spin-ops
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* even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
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* not re-enabled during lock-acquire (which the preempt-spin-ops do):
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*/
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#if !defined(CONFIG_GENERIC_LOCKBREAK) || defined(CONFIG_DEBUG_LOCK_ALLOC)
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static inline unsigned long __raw_spin_lock_irqsave(raw_spinlock_t *lock)
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{
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unsigned long flags;
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local_irq_save(flags);
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preempt_disable();
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spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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/*
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* On lockdep we dont want the hand-coded irq-enable of
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* do_raw_spin_lock_flags() code, because lockdep assumes
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* that interrupts are not re-enabled during lock-acquire:
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*/
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#ifdef CONFIG_LOCKDEP
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LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
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#else
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do_raw_spin_lock_flags(lock, &flags);
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#endif
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return flags;
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}
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static inline void __raw_spin_lock_irq(raw_spinlock_t *lock)
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{
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local_irq_disable();
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preempt_disable();
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spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
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}
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static inline void __raw_spin_lock_bh(raw_spinlock_t *lock)
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{
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__local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
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spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
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}
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static inline void __raw_spin_lock(raw_spinlock_t *lock)
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{
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preempt_disable();
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spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
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}
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#endif /* !CONFIG_GENERIC_LOCKBREAK || CONFIG_DEBUG_LOCK_ALLOC */
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static inline void __raw_spin_unlock(raw_spinlock_t *lock)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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do_raw_spin_unlock(lock);
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preempt_enable();
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}
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static inline void __raw_spin_unlock_irqrestore(raw_spinlock_t *lock,
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unsigned long flags)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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do_raw_spin_unlock(lock);
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local_irq_restore(flags);
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preempt_enable();
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}
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static inline void __raw_spin_unlock_irq(raw_spinlock_t *lock)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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do_raw_spin_unlock(lock);
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local_irq_enable();
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preempt_enable();
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}
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static inline void __raw_spin_unlock_bh(raw_spinlock_t *lock)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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do_raw_spin_unlock(lock);
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__local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
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}
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static inline int __raw_spin_trylock_bh(raw_spinlock_t *lock)
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{
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__local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
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if (do_raw_spin_trylock(lock)) {
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spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
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return 1;
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}
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__local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
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return 0;
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}
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#include <linux/rwlock_api_smp.h>
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#endif /* __LINUX_SPINLOCK_API_SMP_H */
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