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ef6edc9746
On systems running with virtual cpus there is optimization potential in regard to spinlocks and rw-locks. If the virtual cpu that has taken a lock is known to a cpu that wants to acquire the same lock it is beneficial to yield the timeslice of the virtual cpu in favour of the cpu that has the lock (directed yield). With CONFIG_PREEMPT="n" this can be implemented by the architecture without common code changes. Powerpc already does this. With CONFIG_PREEMPT="y" the lock loops are coded with _raw_spin_trylock, _raw_read_trylock and _raw_write_trylock in kernel/spinlock.c. If the lock could not be taken cpu_relax is called. A directed yield is not possible because cpu_relax doesn't know anything about the lock. To be able to yield the lock in favour of the current lock holder variants of cpu_relax for spinlocks and rw-locks are needed. The new _raw_spin_relax, _raw_read_relax and _raw_write_relax primitives differ from cpu_relax insofar that they have an argument: a pointer to the lock structure. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Paul Mackerras <paulus@samba.org> Cc: Haavard Skinnemoen <hskinnemoen@atmel.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
428 lines
10 KiB
C
428 lines
10 KiB
C
/*
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* Copyright (2004) Linus Torvalds
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*
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* Author: Zwane Mwaikambo <zwane@fsmlabs.com>
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*
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* Copyright (2004, 2005) Ingo Molnar
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*
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* This file contains the spinlock/rwlock implementations for the
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* SMP and the DEBUG_SPINLOCK cases. (UP-nondebug inlines them)
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*
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* Note that some architectures have special knowledge about the
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* stack frames of these functions in their profile_pc. If you
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* change anything significant here that could change the stack
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* frame contact the architecture maintainers.
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*/
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#include <linux/linkage.h>
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#include <linux/preempt.h>
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#include <linux/spinlock.h>
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#include <linux/interrupt.h>
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#include <linux/debug_locks.h>
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#include <linux/module.h>
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int __lockfunc _spin_trylock(spinlock_t *lock)
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{
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preempt_disable();
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if (_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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EXPORT_SYMBOL(_spin_trylock);
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int __lockfunc _read_trylock(rwlock_t *lock)
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{
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preempt_disable();
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if (_raw_read_trylock(lock)) {
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rwlock_acquire_read(&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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EXPORT_SYMBOL(_read_trylock);
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int __lockfunc _write_trylock(rwlock_t *lock)
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{
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preempt_disable();
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if (_raw_write_trylock(lock)) {
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rwlock_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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EXPORT_SYMBOL(_write_trylock);
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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_PREEMPT) || !defined(CONFIG_SMP) || \
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defined(CONFIG_DEBUG_LOCK_ALLOC)
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void __lockfunc _read_lock(rwlock_t *lock)
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{
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preempt_disable();
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rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_read_lock(lock);
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}
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EXPORT_SYMBOL(_read_lock);
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unsigned long __lockfunc _spin_lock_irqsave(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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* _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_PROVE_LOCKING
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_raw_spin_lock(lock);
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#else
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_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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EXPORT_SYMBOL(_spin_lock_irqsave);
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void __lockfunc _spin_lock_irq(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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_raw_spin_lock(lock);
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}
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EXPORT_SYMBOL(_spin_lock_irq);
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void __lockfunc _spin_lock_bh(spinlock_t *lock)
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{
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local_bh_disable();
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preempt_disable();
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spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_spin_lock(lock);
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}
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EXPORT_SYMBOL(_spin_lock_bh);
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unsigned long __lockfunc _read_lock_irqsave(rwlock_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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rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_read_lock(lock);
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return flags;
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}
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EXPORT_SYMBOL(_read_lock_irqsave);
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void __lockfunc _read_lock_irq(rwlock_t *lock)
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{
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local_irq_disable();
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preempt_disable();
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rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_read_lock(lock);
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}
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EXPORT_SYMBOL(_read_lock_irq);
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void __lockfunc _read_lock_bh(rwlock_t *lock)
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{
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local_bh_disable();
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preempt_disable();
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rwlock_acquire_read(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_read_lock(lock);
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}
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EXPORT_SYMBOL(_read_lock_bh);
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unsigned long __lockfunc _write_lock_irqsave(rwlock_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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rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_write_lock(lock);
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return flags;
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}
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EXPORT_SYMBOL(_write_lock_irqsave);
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void __lockfunc _write_lock_irq(rwlock_t *lock)
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{
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local_irq_disable();
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preempt_disable();
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rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_write_lock(lock);
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}
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EXPORT_SYMBOL(_write_lock_irq);
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void __lockfunc _write_lock_bh(rwlock_t *lock)
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{
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local_bh_disable();
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preempt_disable();
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rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_write_lock(lock);
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}
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EXPORT_SYMBOL(_write_lock_bh);
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void __lockfunc _spin_lock(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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_raw_spin_lock(lock);
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}
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EXPORT_SYMBOL(_spin_lock);
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void __lockfunc _write_lock(rwlock_t *lock)
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{
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preempt_disable();
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rwlock_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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_raw_write_lock(lock);
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}
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EXPORT_SYMBOL(_write_lock);
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#else /* CONFIG_PREEMPT: */
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/*
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* This could be a long-held lock. We both prepare to spin for a long
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* time (making _this_ CPU preemptable if possible), and we also signal
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* towards that other CPU that it should break the lock ASAP.
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*
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* (We do this in a function because inlining it would be excessive.)
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*/
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#define BUILD_LOCK_OPS(op, locktype) \
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void __lockfunc _##op##_lock(locktype##_t *lock) \
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{ \
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for (;;) { \
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preempt_disable(); \
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if (likely(_raw_##op##_trylock(lock))) \
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break; \
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preempt_enable(); \
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\
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if (!(lock)->break_lock) \
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(lock)->break_lock = 1; \
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while (!op##_can_lock(lock) && (lock)->break_lock) \
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_raw_##op##_relax(&lock->raw_lock); \
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} \
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(lock)->break_lock = 0; \
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} \
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\
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EXPORT_SYMBOL(_##op##_lock); \
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\
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unsigned long __lockfunc _##op##_lock_irqsave(locktype##_t *lock) \
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{ \
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unsigned long flags; \
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\
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for (;;) { \
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preempt_disable(); \
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local_irq_save(flags); \
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if (likely(_raw_##op##_trylock(lock))) \
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break; \
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local_irq_restore(flags); \
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preempt_enable(); \
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\
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if (!(lock)->break_lock) \
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(lock)->break_lock = 1; \
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while (!op##_can_lock(lock) && (lock)->break_lock) \
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_raw_##op##_relax(&lock->raw_lock); \
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} \
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(lock)->break_lock = 0; \
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return flags; \
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} \
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\
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EXPORT_SYMBOL(_##op##_lock_irqsave); \
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\
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void __lockfunc _##op##_lock_irq(locktype##_t *lock) \
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{ \
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_##op##_lock_irqsave(lock); \
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} \
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\
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EXPORT_SYMBOL(_##op##_lock_irq); \
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\
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void __lockfunc _##op##_lock_bh(locktype##_t *lock) \
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{ \
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unsigned long flags; \
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\
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/* */ \
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/* Careful: we must exclude softirqs too, hence the */ \
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/* irq-disabling. We use the generic preemption-aware */ \
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/* function: */ \
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/**/ \
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flags = _##op##_lock_irqsave(lock); \
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local_bh_disable(); \
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local_irq_restore(flags); \
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} \
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\
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EXPORT_SYMBOL(_##op##_lock_bh)
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/*
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* Build preemption-friendly versions of the following
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* lock-spinning functions:
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*
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* _[spin|read|write]_lock()
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* _[spin|read|write]_lock_irq()
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* _[spin|read|write]_lock_irqsave()
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* _[spin|read|write]_lock_bh()
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*/
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BUILD_LOCK_OPS(spin, spinlock);
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BUILD_LOCK_OPS(read, rwlock);
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BUILD_LOCK_OPS(write, rwlock);
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#endif /* CONFIG_PREEMPT */
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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void __lockfunc _spin_lock_nested(spinlock_t *lock, int subclass)
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{
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preempt_disable();
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spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
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_raw_spin_lock(lock);
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}
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EXPORT_SYMBOL(_spin_lock_nested);
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#endif
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void __lockfunc _spin_unlock(spinlock_t *lock)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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_raw_spin_unlock(lock);
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preempt_enable();
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}
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EXPORT_SYMBOL(_spin_unlock);
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void __lockfunc _write_unlock(rwlock_t *lock)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_write_unlock(lock);
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preempt_enable();
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}
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EXPORT_SYMBOL(_write_unlock);
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void __lockfunc _read_unlock(rwlock_t *lock)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_read_unlock(lock);
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preempt_enable();
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}
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EXPORT_SYMBOL(_read_unlock);
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void __lockfunc _spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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_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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EXPORT_SYMBOL(_spin_unlock_irqrestore);
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void __lockfunc _spin_unlock_irq(spinlock_t *lock)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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_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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EXPORT_SYMBOL(_spin_unlock_irq);
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void __lockfunc _spin_unlock_bh(spinlock_t *lock)
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{
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spin_release(&lock->dep_map, 1, _RET_IP_);
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_raw_spin_unlock(lock);
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preempt_enable_no_resched();
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local_bh_enable_ip((unsigned long)__builtin_return_address(0));
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}
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EXPORT_SYMBOL(_spin_unlock_bh);
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void __lockfunc _read_unlock_irqrestore(rwlock_t *lock, unsigned long flags)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_read_unlock(lock);
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local_irq_restore(flags);
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preempt_enable();
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}
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EXPORT_SYMBOL(_read_unlock_irqrestore);
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void __lockfunc _read_unlock_irq(rwlock_t *lock)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_read_unlock(lock);
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local_irq_enable();
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preempt_enable();
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}
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EXPORT_SYMBOL(_read_unlock_irq);
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void __lockfunc _read_unlock_bh(rwlock_t *lock)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_read_unlock(lock);
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preempt_enable_no_resched();
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local_bh_enable_ip((unsigned long)__builtin_return_address(0));
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}
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EXPORT_SYMBOL(_read_unlock_bh);
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void __lockfunc _write_unlock_irqrestore(rwlock_t *lock, unsigned long flags)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_write_unlock(lock);
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local_irq_restore(flags);
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preempt_enable();
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}
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EXPORT_SYMBOL(_write_unlock_irqrestore);
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void __lockfunc _write_unlock_irq(rwlock_t *lock)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_write_unlock(lock);
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local_irq_enable();
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preempt_enable();
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}
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EXPORT_SYMBOL(_write_unlock_irq);
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void __lockfunc _write_unlock_bh(rwlock_t *lock)
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{
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rwlock_release(&lock->dep_map, 1, _RET_IP_);
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_raw_write_unlock(lock);
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preempt_enable_no_resched();
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local_bh_enable_ip((unsigned long)__builtin_return_address(0));
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}
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EXPORT_SYMBOL(_write_unlock_bh);
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int __lockfunc _spin_trylock_bh(spinlock_t *lock)
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{
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local_bh_disable();
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preempt_disable();
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if (_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_no_resched();
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local_bh_enable_ip((unsigned long)__builtin_return_address(0));
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return 0;
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}
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EXPORT_SYMBOL(_spin_trylock_bh);
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int in_lock_functions(unsigned long addr)
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{
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/* Linker adds these: start and end of __lockfunc functions */
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extern char __lock_text_start[], __lock_text_end[];
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return addr >= (unsigned long)__lock_text_start
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&& addr < (unsigned long)__lock_text_end;
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}
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EXPORT_SYMBOL(in_lock_functions);
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