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linux-next/include/linux/spinlock_api_smp.h
Peter Zijlstra 9ea4c38006 locking: Optimize lock_bh functions
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>
2014-01-13 13:47:36 +01:00

193 lines
5.4 KiB
C

#ifndef __LINUX_SPINLOCK_API_SMP_H
#define __LINUX_SPINLOCK_API_SMP_H
#ifndef __LINUX_SPINLOCK_H
# error "please don't include this file directly"
#endif
/*
* include/linux/spinlock_api_smp.h
*
* spinlock API declarations on SMP (and debug)
* (implemented in kernel/spinlock.c)
*
* portions Copyright 2005, Red Hat, Inc., Ingo Molnar
* Released under the General Public License (GPL).
*/
int in_lock_functions(unsigned long addr);
#define assert_raw_spin_locked(x) BUG_ON(!raw_spin_is_locked(x))
void __lockfunc _raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
void __lockfunc _raw_spin_lock_nested(raw_spinlock_t *lock, int subclass)
__acquires(lock);
void __lockfunc
_raw_spin_lock_nest_lock(raw_spinlock_t *lock, struct lockdep_map *map)
__acquires(lock);
void __lockfunc _raw_spin_lock_bh(raw_spinlock_t *lock) __acquires(lock);
void __lockfunc _raw_spin_lock_irq(raw_spinlock_t *lock)
__acquires(lock);
unsigned long __lockfunc _raw_spin_lock_irqsave(raw_spinlock_t *lock)
__acquires(lock);
unsigned long __lockfunc
_raw_spin_lock_irqsave_nested(raw_spinlock_t *lock, int subclass)
__acquires(lock);
int __lockfunc _raw_spin_trylock(raw_spinlock_t *lock);
int __lockfunc _raw_spin_trylock_bh(raw_spinlock_t *lock);
void __lockfunc _raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
void __lockfunc _raw_spin_unlock_bh(raw_spinlock_t *lock) __releases(lock);
void __lockfunc _raw_spin_unlock_irq(raw_spinlock_t *lock) __releases(lock);
void __lockfunc
_raw_spin_unlock_irqrestore(raw_spinlock_t *lock, unsigned long flags)
__releases(lock);
#ifdef CONFIG_INLINE_SPIN_LOCK
#define _raw_spin_lock(lock) __raw_spin_lock(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_LOCK_BH
#define _raw_spin_lock_bh(lock) __raw_spin_lock_bh(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_LOCK_IRQ
#define _raw_spin_lock_irq(lock) __raw_spin_lock_irq(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_LOCK_IRQSAVE
#define _raw_spin_lock_irqsave(lock) __raw_spin_lock_irqsave(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_TRYLOCK
#define _raw_spin_trylock(lock) __raw_spin_trylock(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_TRYLOCK_BH
#define _raw_spin_trylock_bh(lock) __raw_spin_trylock_bh(lock)
#endif
#ifndef CONFIG_UNINLINE_SPIN_UNLOCK
#define _raw_spin_unlock(lock) __raw_spin_unlock(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_UNLOCK_BH
#define _raw_spin_unlock_bh(lock) __raw_spin_unlock_bh(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_UNLOCK_IRQ
#define _raw_spin_unlock_irq(lock) __raw_spin_unlock_irq(lock)
#endif
#ifdef CONFIG_INLINE_SPIN_UNLOCK_IRQRESTORE
#define _raw_spin_unlock_irqrestore(lock, flags) __raw_spin_unlock_irqrestore(lock, flags)
#endif
static inline int __raw_spin_trylock(raw_spinlock_t *lock)
{
preempt_disable();
if (do_raw_spin_trylock(lock)) {
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
return 1;
}
preempt_enable();
return 0;
}
/*
* If lockdep is enabled then we use the non-preemption spin-ops
* even on CONFIG_PREEMPT, because lockdep assumes that interrupts are
* not re-enabled during lock-acquire (which the preempt-spin-ops do):
*/
#if !defined(CONFIG_GENERIC_LOCKBREAK) || defined(CONFIG_DEBUG_LOCK_ALLOC)
static inline unsigned long __raw_spin_lock_irqsave(raw_spinlock_t *lock)
{
unsigned long flags;
local_irq_save(flags);
preempt_disable();
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
/*
* On lockdep we dont want the hand-coded irq-enable of
* do_raw_spin_lock_flags() code, because lockdep assumes
* that interrupts are not re-enabled during lock-acquire:
*/
#ifdef CONFIG_LOCKDEP
LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
#else
do_raw_spin_lock_flags(lock, &flags);
#endif
return flags;
}
static inline void __raw_spin_lock_irq(raw_spinlock_t *lock)
{
local_irq_disable();
preempt_disable();
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
}
static inline void __raw_spin_lock_bh(raw_spinlock_t *lock)
{
__local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
}
static inline void __raw_spin_lock(raw_spinlock_t *lock)
{
preempt_disable();
spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
LOCK_CONTENDED(lock, do_raw_spin_trylock, do_raw_spin_lock);
}
#endif /* !CONFIG_GENERIC_LOCKBREAK || CONFIG_DEBUG_LOCK_ALLOC */
static inline void __raw_spin_unlock(raw_spinlock_t *lock)
{
spin_release(&lock->dep_map, 1, _RET_IP_);
do_raw_spin_unlock(lock);
preempt_enable();
}
static inline void __raw_spin_unlock_irqrestore(raw_spinlock_t *lock,
unsigned long flags)
{
spin_release(&lock->dep_map, 1, _RET_IP_);
do_raw_spin_unlock(lock);
local_irq_restore(flags);
preempt_enable();
}
static inline void __raw_spin_unlock_irq(raw_spinlock_t *lock)
{
spin_release(&lock->dep_map, 1, _RET_IP_);
do_raw_spin_unlock(lock);
local_irq_enable();
preempt_enable();
}
static inline void __raw_spin_unlock_bh(raw_spinlock_t *lock)
{
spin_release(&lock->dep_map, 1, _RET_IP_);
do_raw_spin_unlock(lock);
__local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
}
static inline int __raw_spin_trylock_bh(raw_spinlock_t *lock)
{
__local_bh_disable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
if (do_raw_spin_trylock(lock)) {
spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
return 1;
}
__local_bh_enable_ip(_RET_IP_, SOFTIRQ_LOCK_OFFSET);
return 0;
}
#include <linux/rwlock_api_smp.h>
#endif /* __LINUX_SPINLOCK_API_SMP_H */