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kernel/include/linux/spinlock.h
Samuel Thibault 10f02d1c59 [PATCH] spin_unlock_bh() and preempt_check_resched() 
In _spin_unlock_bh(lock):
	do { \
		_raw_spin_unlock(lock); \
		preempt_enable(); \
		local_bh_enable(); \
		__release(lock); \
	} while (0)

there is no reason for using preempt_enable() instead of a simple
preempt_enable_no_resched()

Since we know bottom halves are disabled, preempt_schedule() will always
return at once (preempt_count!=0), and hence preempt_check_resched() is
useless here...

This fixes it by using "preempt_enable_no_resched()" instead of the
"preempt_enable()", and thus avoids the useless preempt_check_resched()
just before re-enabling bottom halves.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-21 10:46:48 -07:00

606 lines
16 KiB
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#ifndef __LINUX_SPINLOCK_H
#define __LINUX_SPINLOCK_H
/*
* include/linux/spinlock.h - generic locking declarations
*/
#include <linux/config.h>
#include <linux/preempt.h>
#include <linux/linkage.h>
#include <linux/compiler.h>
#include <linux/thread_info.h>
#include <linux/kernel.h>
#include <linux/stringify.h>
#include <asm/processor.h> /* for cpu relax */
#include <asm/system.h>
/*
* Must define these before including other files, inline functions need them
*/
#define LOCK_SECTION_NAME \
".text.lock." __stringify(KBUILD_BASENAME)
#define LOCK_SECTION_START(extra) \
".subsection 1\n\t" \
extra \
".ifndef " LOCK_SECTION_NAME "\n\t" \
LOCK_SECTION_NAME ":\n\t" \
".endif\n"
#define LOCK_SECTION_END \
".previous\n\t"
#define __lockfunc fastcall __attribute__((section(".spinlock.text")))
/*
* If CONFIG_SMP is set, pull in the _raw_* definitions
*/
#ifdef CONFIG_SMP
#define assert_spin_locked(x) BUG_ON(!spin_is_locked(x))
#include <asm/spinlock.h>
int __lockfunc _spin_trylock(spinlock_t *lock);
int __lockfunc _read_trylock(rwlock_t *lock);
int __lockfunc _write_trylock(rwlock_t *lock);
void __lockfunc _spin_lock(spinlock_t *lock) __acquires(spinlock_t);
void __lockfunc _read_lock(rwlock_t *lock) __acquires(rwlock_t);
void __lockfunc _write_lock(rwlock_t *lock) __acquires(rwlock_t);
void __lockfunc _spin_unlock(spinlock_t *lock) __releases(spinlock_t);
void __lockfunc _read_unlock(rwlock_t *lock) __releases(rwlock_t);
void __lockfunc _write_unlock(rwlock_t *lock) __releases(rwlock_t);
unsigned long __lockfunc _spin_lock_irqsave(spinlock_t *lock) __acquires(spinlock_t);
unsigned long __lockfunc _read_lock_irqsave(rwlock_t *lock) __acquires(rwlock_t);
unsigned long __lockfunc _write_lock_irqsave(rwlock_t *lock) __acquires(rwlock_t);
void __lockfunc _spin_lock_irq(spinlock_t *lock) __acquires(spinlock_t);
void __lockfunc _spin_lock_bh(spinlock_t *lock) __acquires(spinlock_t);
void __lockfunc _read_lock_irq(rwlock_t *lock) __acquires(rwlock_t);
void __lockfunc _read_lock_bh(rwlock_t *lock) __acquires(rwlock_t);
void __lockfunc _write_lock_irq(rwlock_t *lock) __acquires(rwlock_t);
void __lockfunc _write_lock_bh(rwlock_t *lock) __acquires(rwlock_t);
void __lockfunc _spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags) __releases(spinlock_t);
void __lockfunc _spin_unlock_irq(spinlock_t *lock) __releases(spinlock_t);
void __lockfunc _spin_unlock_bh(spinlock_t *lock) __releases(spinlock_t);
void __lockfunc _read_unlock_irqrestore(rwlock_t *lock, unsigned long flags) __releases(rwlock_t);
void __lockfunc _read_unlock_irq(rwlock_t *lock) __releases(rwlock_t);
void __lockfunc _read_unlock_bh(rwlock_t *lock) __releases(rwlock_t);
void __lockfunc _write_unlock_irqrestore(rwlock_t *lock, unsigned long flags) __releases(rwlock_t);
void __lockfunc _write_unlock_irq(rwlock_t *lock) __releases(rwlock_t);
void __lockfunc _write_unlock_bh(rwlock_t *lock) __releases(rwlock_t);
int __lockfunc _spin_trylock_bh(spinlock_t *lock);
int __lockfunc generic_raw_read_trylock(rwlock_t *lock);
int in_lock_functions(unsigned long addr);
#else
#define in_lock_functions(ADDR) 0
#if !defined(CONFIG_PREEMPT) && !defined(CONFIG_DEBUG_SPINLOCK)
# define _atomic_dec_and_lock(atomic,lock) atomic_dec_and_test(atomic)
# define ATOMIC_DEC_AND_LOCK
#endif
#ifdef CONFIG_DEBUG_SPINLOCK
#define SPINLOCK_MAGIC 0x1D244B3C
typedef struct {
unsigned long magic;
volatile unsigned long lock;
volatile unsigned int babble;
const char *module;
char *owner;
int oline;
} spinlock_t;
#define SPIN_LOCK_UNLOCKED (spinlock_t) { SPINLOCK_MAGIC, 0, 10, __FILE__ , NULL, 0}
#define spin_lock_init(x) \
do { \
(x)->magic = SPINLOCK_MAGIC; \
(x)->lock = 0; \
(x)->babble = 5; \
(x)->module = __FILE__; \
(x)->owner = NULL; \
(x)->oline = 0; \
} while (0)
#define CHECK_LOCK(x) \
do { \
if ((x)->magic != SPINLOCK_MAGIC) { \
printk(KERN_ERR "%s:%d: spin_is_locked on uninitialized spinlock %p.\n", \
__FILE__, __LINE__, (x)); \
} \
} while(0)
#define _raw_spin_lock(x) \
do { \
CHECK_LOCK(x); \
if ((x)->lock&&(x)->babble) { \
(x)->babble--; \
printk("%s:%d: spin_lock(%s:%p) already locked by %s/%d\n", \
__FILE__,__LINE__, (x)->module, \
(x), (x)->owner, (x)->oline); \
} \
(x)->lock = 1; \
(x)->owner = __FILE__; \
(x)->oline = __LINE__; \
} while (0)
/* without debugging, spin_is_locked on UP always says
* FALSE. --> printk if already locked. */
#define spin_is_locked(x) \
({ \
CHECK_LOCK(x); \
if ((x)->lock&&(x)->babble) { \
(x)->babble--; \
printk("%s:%d: spin_is_locked(%s:%p) already locked by %s/%d\n", \
__FILE__,__LINE__, (x)->module, \
(x), (x)->owner, (x)->oline); \
} \
0; \
})
/* with debugging, assert_spin_locked() on UP does check
* the lock value properly */
#define assert_spin_locked(x) \
({ \
CHECK_LOCK(x); \
BUG_ON(!(x)->lock); \
})
/* without debugging, spin_trylock on UP always says
* TRUE. --> printk if already locked. */
#define _raw_spin_trylock(x) \
({ \
CHECK_LOCK(x); \
if ((x)->lock&&(x)->babble) { \
(x)->babble--; \
printk("%s:%d: spin_trylock(%s:%p) already locked by %s/%d\n", \
__FILE__,__LINE__, (x)->module, \
(x), (x)->owner, (x)->oline); \
} \
(x)->lock = 1; \
(x)->owner = __FILE__; \
(x)->oline = __LINE__; \
1; \
})
#define spin_unlock_wait(x) \
do { \
CHECK_LOCK(x); \
if ((x)->lock&&(x)->babble) { \
(x)->babble--; \
printk("%s:%d: spin_unlock_wait(%s:%p) owned by %s/%d\n", \
__FILE__,__LINE__, (x)->module, (x), \
(x)->owner, (x)->oline); \
}\
} while (0)
#define _raw_spin_unlock(x) \
do { \
CHECK_LOCK(x); \
if (!(x)->lock&&(x)->babble) { \
(x)->babble--; \
printk("%s:%d: spin_unlock(%s:%p) not locked\n", \
__FILE__,__LINE__, (x)->module, (x));\
} \
(x)->lock = 0; \
} while (0)
#else
/*
* gcc versions before ~2.95 have a nasty bug with empty initializers.
*/
#if (__GNUC__ > 2)
typedef struct { } spinlock_t;
#define SPIN_LOCK_UNLOCKED (spinlock_t) { }
#else
typedef struct { int gcc_is_buggy; } spinlock_t;
#define SPIN_LOCK_UNLOCKED (spinlock_t) { 0 }
#endif
/*
* If CONFIG_SMP is unset, declare the _raw_* definitions as nops
*/
#define spin_lock_init(lock) do { (void)(lock); } while(0)
#define _raw_spin_lock(lock) do { (void)(lock); } while(0)
#define spin_is_locked(lock) ((void)(lock), 0)
#define assert_spin_locked(lock) do { (void)(lock); } while(0)
#define _raw_spin_trylock(lock) (((void)(lock), 1))
#define spin_unlock_wait(lock) (void)(lock)
#define _raw_spin_unlock(lock) do { (void)(lock); } while(0)
#endif /* CONFIG_DEBUG_SPINLOCK */
/* RW spinlocks: No debug version */
#if (__GNUC__ > 2)
typedef struct { } rwlock_t;
#define RW_LOCK_UNLOCKED (rwlock_t) { }
#else
typedef struct { int gcc_is_buggy; } rwlock_t;
#define RW_LOCK_UNLOCKED (rwlock_t) { 0 }
#endif
#define rwlock_init(lock) do { (void)(lock); } while(0)
#define _raw_read_lock(lock) do { (void)(lock); } while(0)
#define _raw_read_unlock(lock) do { (void)(lock); } while(0)
#define _raw_write_lock(lock) do { (void)(lock); } while(0)
#define _raw_write_unlock(lock) do { (void)(lock); } while(0)
#define read_can_lock(lock) (((void)(lock), 1))
#define write_can_lock(lock) (((void)(lock), 1))
#define _raw_read_trylock(lock) ({ (void)(lock); (1); })
#define _raw_write_trylock(lock) ({ (void)(lock); (1); })
#define _spin_trylock(lock) ({preempt_disable(); _raw_spin_trylock(lock) ? \
1 : ({preempt_enable(); 0;});})
#define _read_trylock(lock) ({preempt_disable();_raw_read_trylock(lock) ? \
1 : ({preempt_enable(); 0;});})
#define _write_trylock(lock) ({preempt_disable(); _raw_write_trylock(lock) ? \
1 : ({preempt_enable(); 0;});})
#define _spin_trylock_bh(lock) ({preempt_disable(); local_bh_disable(); \
_raw_spin_trylock(lock) ? \
1 : ({preempt_enable_no_resched(); local_bh_enable(); 0;});})
#define _spin_lock(lock) \
do { \
preempt_disable(); \
_raw_spin_lock(lock); \
__acquire(lock); \
} while(0)
#define _write_lock(lock) \
do { \
preempt_disable(); \
_raw_write_lock(lock); \
__acquire(lock); \
} while(0)
#define _read_lock(lock) \
do { \
preempt_disable(); \
_raw_read_lock(lock); \
__acquire(lock); \
} while(0)
#define _spin_unlock(lock) \
do { \
_raw_spin_unlock(lock); \
preempt_enable(); \
__release(lock); \
} while (0)
#define _write_unlock(lock) \
do { \
_raw_write_unlock(lock); \
preempt_enable(); \
__release(lock); \
} while(0)
#define _read_unlock(lock) \
do { \
_raw_read_unlock(lock); \
preempt_enable(); \
__release(lock); \
} while(0)
#define _spin_lock_irqsave(lock, flags) \
do { \
local_irq_save(flags); \
preempt_disable(); \
_raw_spin_lock(lock); \
__acquire(lock); \
} while (0)
#define _spin_lock_irq(lock) \
do { \
local_irq_disable(); \
preempt_disable(); \
_raw_spin_lock(lock); \
__acquire(lock); \
} while (0)
#define _spin_lock_bh(lock) \
do { \
local_bh_disable(); \
preempt_disable(); \
_raw_spin_lock(lock); \
__acquire(lock); \
} while (0)
#define _read_lock_irqsave(lock, flags) \
do { \
local_irq_save(flags); \
preempt_disable(); \
_raw_read_lock(lock); \
__acquire(lock); \
} while (0)
#define _read_lock_irq(lock) \
do { \
local_irq_disable(); \
preempt_disable(); \
_raw_read_lock(lock); \
__acquire(lock); \
} while (0)
#define _read_lock_bh(lock) \
do { \
local_bh_disable(); \
preempt_disable(); \
_raw_read_lock(lock); \
__acquire(lock); \
} while (0)
#define _write_lock_irqsave(lock, flags) \
do { \
local_irq_save(flags); \
preempt_disable(); \
_raw_write_lock(lock); \
__acquire(lock); \
} while (0)
#define _write_lock_irq(lock) \
do { \
local_irq_disable(); \
preempt_disable(); \
_raw_write_lock(lock); \
__acquire(lock); \
} while (0)
#define _write_lock_bh(lock) \
do { \
local_bh_disable(); \
preempt_disable(); \
_raw_write_lock(lock); \
__acquire(lock); \
} while (0)
#define _spin_unlock_irqrestore(lock, flags) \
do { \
_raw_spin_unlock(lock); \
local_irq_restore(flags); \
preempt_enable(); \
__release(lock); \
} while (0)
#define _spin_unlock_irq(lock) \
do { \
_raw_spin_unlock(lock); \
local_irq_enable(); \
preempt_enable(); \
__release(lock); \
} while (0)
#define _spin_unlock_bh(lock) \
do { \
_raw_spin_unlock(lock); \
preempt_enable_no_resched(); \
local_bh_enable(); \
__release(lock); \
} while (0)
#define _write_unlock_bh(lock) \
do { \
_raw_write_unlock(lock); \
preempt_enable_no_resched(); \
local_bh_enable(); \
__release(lock); \
} while (0)
#define _read_unlock_irqrestore(lock, flags) \
do { \
_raw_read_unlock(lock); \
local_irq_restore(flags); \
preempt_enable(); \
__release(lock); \
} while (0)
#define _write_unlock_irqrestore(lock, flags) \
do { \
_raw_write_unlock(lock); \
local_irq_restore(flags); \
preempt_enable(); \
__release(lock); \
} while (0)
#define _read_unlock_irq(lock) \
do { \
_raw_read_unlock(lock); \
local_irq_enable(); \
preempt_enable(); \
__release(lock); \
} while (0)
#define _read_unlock_bh(lock) \
do { \
_raw_read_unlock(lock); \
preempt_enable_no_resched(); \
local_bh_enable(); \
__release(lock); \
} while (0)
#define _write_unlock_irq(lock) \
do { \
_raw_write_unlock(lock); \
local_irq_enable(); \
preempt_enable(); \
__release(lock); \
} while (0)
#endif /* !SMP */
/*
* Define the various spin_lock and rw_lock methods. Note we define these
* regardless of whether CONFIG_SMP or CONFIG_PREEMPT are set. The various
* methods are defined as nops in the case they are not required.
*/
#define spin_trylock(lock) __cond_lock(_spin_trylock(lock))
#define read_trylock(lock) __cond_lock(_read_trylock(lock))
#define write_trylock(lock) __cond_lock(_write_trylock(lock))
#define spin_lock(lock) _spin_lock(lock)
#define write_lock(lock) _write_lock(lock)
#define read_lock(lock) _read_lock(lock)
#ifdef CONFIG_SMP
#define spin_lock_irqsave(lock, flags) flags = _spin_lock_irqsave(lock)
#define read_lock_irqsave(lock, flags) flags = _read_lock_irqsave(lock)
#define write_lock_irqsave(lock, flags) flags = _write_lock_irqsave(lock)
#else
#define spin_lock_irqsave(lock, flags) _spin_lock_irqsave(lock, flags)
#define read_lock_irqsave(lock, flags) _read_lock_irqsave(lock, flags)
#define write_lock_irqsave(lock, flags) _write_lock_irqsave(lock, flags)
#endif
#define spin_lock_irq(lock) _spin_lock_irq(lock)
#define spin_lock_bh(lock) _spin_lock_bh(lock)
#define read_lock_irq(lock) _read_lock_irq(lock)
#define read_lock_bh(lock) _read_lock_bh(lock)
#define write_lock_irq(lock) _write_lock_irq(lock)
#define write_lock_bh(lock) _write_lock_bh(lock)
#define spin_unlock(lock) _spin_unlock(lock)
#define write_unlock(lock) _write_unlock(lock)
#define read_unlock(lock) _read_unlock(lock)
#define spin_unlock_irqrestore(lock, flags) _spin_unlock_irqrestore(lock, flags)
#define spin_unlock_irq(lock) _spin_unlock_irq(lock)
#define spin_unlock_bh(lock) _spin_unlock_bh(lock)
#define read_unlock_irqrestore(lock, flags) _read_unlock_irqrestore(lock, flags)
#define read_unlock_irq(lock) _read_unlock_irq(lock)
#define read_unlock_bh(lock) _read_unlock_bh(lock)
#define write_unlock_irqrestore(lock, flags) _write_unlock_irqrestore(lock, flags)
#define write_unlock_irq(lock) _write_unlock_irq(lock)
#define write_unlock_bh(lock) _write_unlock_bh(lock)
#define spin_trylock_bh(lock) __cond_lock(_spin_trylock_bh(lock))
#define spin_trylock_irq(lock) \
({ \
local_irq_disable(); \
_spin_trylock(lock) ? \
1 : ({local_irq_enable(); 0; }); \
})
#define spin_trylock_irqsave(lock, flags) \
({ \
local_irq_save(flags); \
_spin_trylock(lock) ? \
1 : ({local_irq_restore(flags); 0;}); \
})
#ifdef CONFIG_LOCKMETER
extern void _metered_spin_lock (spinlock_t *lock);
extern void _metered_spin_unlock (spinlock_t *lock);
extern int _metered_spin_trylock(spinlock_t *lock);
extern void _metered_read_lock (rwlock_t *lock);
extern void _metered_read_unlock (rwlock_t *lock);
extern void _metered_write_lock (rwlock_t *lock);
extern void _metered_write_unlock (rwlock_t *lock);
extern int _metered_read_trylock (rwlock_t *lock);
extern int _metered_write_trylock(rwlock_t *lock);
#endif
/* "lock on reference count zero" */
#ifndef ATOMIC_DEC_AND_LOCK
#include <asm/atomic.h>
extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
#endif
#define atomic_dec_and_lock(atomic,lock) __cond_lock(_atomic_dec_and_lock(atomic,lock))
/*
* bit-based spin_lock()
*
* Don't use this unless you really need to: spin_lock() and spin_unlock()
* are significantly faster.
*/
static inline void bit_spin_lock(int bitnum, unsigned long *addr)
{
/*
* Assuming the lock is uncontended, this never enters
* the body of the outer loop. If it is contended, then
* within the inner loop a non-atomic test is used to
* busywait with less bus contention for a good time to
* attempt to acquire the lock bit.
*/
preempt_disable();
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
while (test_and_set_bit(bitnum, addr)) {
while (test_bit(bitnum, addr)) {
preempt_enable();
cpu_relax();
preempt_disable();
}
}
#endif
__acquire(bitlock);
}
/*
* Return true if it was acquired
*/
static inline int bit_spin_trylock(int bitnum, unsigned long *addr)
{
preempt_disable();
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
if (test_and_set_bit(bitnum, addr)) {
preempt_enable();
return 0;
}
#endif
__acquire(bitlock);
return 1;
}
/*
* bit-based spin_unlock()
*/
static inline void bit_spin_unlock(int bitnum, unsigned long *addr)
{
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
BUG_ON(!test_bit(bitnum, addr));
smp_mb__before_clear_bit();
clear_bit(bitnum, addr);
#endif
preempt_enable();
__release(bitlock);
}
/*
* Return true if the lock is held.
*/
static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
{
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
return test_bit(bitnum, addr);
#elif defined CONFIG_PREEMPT
return preempt_count();
#else
return 1;
#endif
}
#define DEFINE_SPINLOCK(x) spinlock_t x = SPIN_LOCK_UNLOCKED
#define DEFINE_RWLOCK(x) rwlock_t x = RW_LOCK_UNLOCKED
/**
* spin_can_lock - would spin_trylock() succeed?
* @lock: the spinlock in question.
*/
#define spin_can_lock(lock) (!spin_is_locked(lock))
#endif /* __LINUX_SPINLOCK_H */
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