[PATCH] x86_64: Remove asm-x86_64/rwsem.h
Not needed since x86-64 always uses the spinlock based rwsems. Signed-off-by: Andi Kleen <ak@suse.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andi Kleen
Linus Torvalds
parent
a5b250a428
commit
8e0d4f4e91
|
|
@ -1,283 +0,0 @@
|
||||||
/* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for x86_64+
|
|
||||||
*
|
|
||||||
* Written by David Howells (dhowells@redhat.com).
|
|
||||||
* Ported by Andi Kleen <ak@suse.de> to x86-64.
|
|
||||||
*
|
|
||||||
* Derived from asm-i386/semaphore.h and asm-i386/rwsem.h
|
|
||||||
*
|
|
||||||
*
|
|
||||||
* The MSW of the count is the negated number of active writers and waiting
|
|
||||||
* lockers, and the LSW is the total number of active locks
|
|
||||||
*
|
|
||||||
* The lock count is initialized to 0 (no active and no waiting lockers).
|
|
||||||
*
|
|
||||||
* When a writer subtracts WRITE_BIAS, it'll get 0xffff0001 for the case of an
|
|
||||||
* uncontended lock. This can be determined because XADD returns the old value.
|
|
||||||
* Readers increment by 1 and see a positive value when uncontended, negative
|
|
||||||
* if there are writers (and maybe) readers waiting (in which case it goes to
|
|
||||||
* sleep).
|
|
||||||
*
|
|
||||||
* The value of WAITING_BIAS supports up to 32766 waiting processes. This can
|
|
||||||
* be extended to 65534 by manually checking the whole MSW rather than relying
|
|
||||||
* on the S flag.
|
|
||||||
*
|
|
||||||
* The value of ACTIVE_BIAS supports up to 65535 active processes.
|
|
||||||
*
|
|
||||||
* This should be totally fair - if anything is waiting, a process that wants a
|
|
||||||
* lock will go to the back of the queue. When the currently active lock is
|
|
||||||
* released, if there's a writer at the front of the queue, then that and only
|
|
||||||
* that will be woken up; if there's a bunch of consecutive readers at the
|
|
||||||
* front, then they'll all be woken up, but no other readers will be.
|
|
||||||
*/
|
|
||||||
|
|
||||||
#ifndef _X8664_RWSEM_H
|
|
||||||
#define _X8664_RWSEM_H
|
|
||||||
|
|
||||||
#ifndef _LINUX_RWSEM_H
|
|
||||||
#error "please don't include asm/rwsem.h directly, use linux/rwsem.h instead"
|
|
||||||
#endif
|
|
||||||
|
|
||||||
#ifdef __KERNEL__
|
|
||||||
|
|
||||||
#include <linux/list.h>
|
|
||||||
#include <linux/spinlock.h>
|
|
||||||
|
|
||||||
struct rwsem_waiter;
|
|
||||||
|
|
||||||
extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
|
|
||||||
extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
|
|
||||||
extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *);
|
|
||||||
extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
|
|
||||||
|
|
||||||
/*
|
|
||||||
* the semaphore definition
|
|
||||||
*/
|
|
||||||
struct rw_semaphore {
|
|
||||||
signed int count;
|
|
||||||
#define RWSEM_UNLOCKED_VALUE 0x00000000
|
|
||||||
#define RWSEM_ACTIVE_BIAS 0x00000001
|
|
||||||
#define RWSEM_ACTIVE_MASK 0x0000ffff
|
|
||||||
#define RWSEM_WAITING_BIAS (-0x00010000)
|
|
||||||
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
|
|
||||||
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
|
|
||||||
spinlock_t wait_lock;
|
|
||||||
struct list_head wait_list;
|
|
||||||
#if RWSEM_DEBUG
|
|
||||||
int debug;
|
|
||||||
#endif
|
|
||||||
};
|
|
||||||
|
|
||||||
/*
|
|
||||||
* initialisation
|
|
||||||
*/
|
|
||||||
#if RWSEM_DEBUG
|
|
||||||
#define __RWSEM_DEBUG_INIT , 0
|
|
||||||
#else
|
|
||||||
#define __RWSEM_DEBUG_INIT /* */
|
|
||||||
#endif
|
|
||||||
|
|
||||||
#define __RWSEM_INITIALIZER(name) \
|
|
||||||
{ RWSEM_UNLOCKED_VALUE, SPIN_LOCK_UNLOCKED, LIST_HEAD_INIT((name).wait_list) \
|
|
||||||
__RWSEM_DEBUG_INIT }
|
|
||||||
|
|
||||||
#define DECLARE_RWSEM(name) \
|
|
||||||
struct rw_semaphore name = __RWSEM_INITIALIZER(name)
|
|
||||||
|
|
||||||
static inline void init_rwsem(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
sem->count = RWSEM_UNLOCKED_VALUE;
|
|
||||||
spin_lock_init(&sem->wait_lock);
|
|
||||||
INIT_LIST_HEAD(&sem->wait_list);
|
|
||||||
#if RWSEM_DEBUG
|
|
||||||
sem->debug = 0;
|
|
||||||
#endif
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* lock for reading
|
|
||||||
*/
|
|
||||||
static inline void __down_read(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
__asm__ __volatile__(
|
|
||||||
"# beginning down_read\n\t"
|
|
||||||
LOCK_PREFIX " incl (%%rdi)\n\t" /* adds 0x00000001, returns the old value */
|
|
||||||
" js 2f\n\t" /* jump if we weren't granted the lock */
|
|
||||||
"1:\n\t"
|
|
||||||
LOCK_SECTION_START("") \
|
|
||||||
"2:\n\t"
|
|
||||||
" call rwsem_down_read_failed_thunk\n\t"
|
|
||||||
" jmp 1b\n"
|
|
||||||
LOCK_SECTION_END \
|
|
||||||
"# ending down_read\n\t"
|
|
||||||
: "+m"(sem->count)
|
|
||||||
: "D"(sem)
|
|
||||||
: "memory", "cc");
|
|
||||||
}
|
|
||||||
|
|
||||||
|
|
||||||
/*
|
|
||||||
* trylock for reading -- returns 1 if successful, 0 if contention
|
|
||||||
*/
|
|
||||||
static inline int __down_read_trylock(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
__s32 result, tmp;
|
|
||||||
__asm__ __volatile__(
|
|
||||||
"# beginning __down_read_trylock\n\t"
|
|
||||||
" movl %0,%1\n\t"
|
|
||||||
"1:\n\t"
|
|
||||||
" movl %1,%2\n\t"
|
|
||||||
" addl %3,%2\n\t"
|
|
||||||
" jle 2f\n\t"
|
|
||||||
LOCK_PREFIX " cmpxchgl %2,%0\n\t"
|
|
||||||
" jnz 1b\n\t"
|
|
||||||
"2:\n\t"
|
|
||||||
"# ending __down_read_trylock\n\t"
|
|
||||||
: "+m"(sem->count), "=&a"(result), "=&r"(tmp)
|
|
||||||
: "i"(RWSEM_ACTIVE_READ_BIAS)
|
|
||||||
: "memory", "cc");
|
|
||||||
return result>=0 ? 1 : 0;
|
|
||||||
}
|
|
||||||
|
|
||||||
|
|
||||||
/*
|
|
||||||
* lock for writing
|
|
||||||
*/
|
|
||||||
static inline void __down_write(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
int tmp;
|
|
||||||
|
|
||||||
tmp = RWSEM_ACTIVE_WRITE_BIAS;
|
|
||||||
__asm__ __volatile__(
|
|
||||||
"# beginning down_write\n\t"
|
|
||||||
LOCK_PREFIX " xaddl %0,(%%rdi)\n\t" /* subtract 0x0000ffff, returns the old value */
|
|
||||||
" testl %0,%0\n\t" /* was the count 0 before? */
|
|
||||||
" jnz 2f\n\t" /* jump if we weren't granted the lock */
|
|
||||||
"1:\n\t"
|
|
||||||
LOCK_SECTION_START("")
|
|
||||||
"2:\n\t"
|
|
||||||
" call rwsem_down_write_failed_thunk\n\t"
|
|
||||||
" jmp 1b\n"
|
|
||||||
LOCK_SECTION_END
|
|
||||||
"# ending down_write"
|
|
||||||
: "=&r" (tmp)
|
|
||||||
: "0"(tmp), "D"(sem)
|
|
||||||
: "memory", "cc");
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* trylock for writing -- returns 1 if successful, 0 if contention
|
|
||||||
*/
|
|
||||||
static inline int __down_write_trylock(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
signed long ret = cmpxchg(&sem->count,
|
|
||||||
RWSEM_UNLOCKED_VALUE,
|
|
||||||
RWSEM_ACTIVE_WRITE_BIAS);
|
|
||||||
if (ret == RWSEM_UNLOCKED_VALUE)
|
|
||||||
return 1;
|
|
||||||
return 0;
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* unlock after reading
|
|
||||||
*/
|
|
||||||
static inline void __up_read(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
__s32 tmp = -RWSEM_ACTIVE_READ_BIAS;
|
|
||||||
__asm__ __volatile__(
|
|
||||||
"# beginning __up_read\n\t"
|
|
||||||
LOCK_PREFIX " xaddl %[tmp],(%%rdi)\n\t" /* subtracts 1, returns the old value */
|
|
||||||
" js 2f\n\t" /* jump if the lock is being waited upon */
|
|
||||||
"1:\n\t"
|
|
||||||
LOCK_SECTION_START("")
|
|
||||||
"2:\n\t"
|
|
||||||
" decw %w[tmp]\n\t" /* do nothing if still outstanding active readers */
|
|
||||||
" jnz 1b\n\t"
|
|
||||||
" call rwsem_wake_thunk\n\t"
|
|
||||||
" jmp 1b\n"
|
|
||||||
LOCK_SECTION_END
|
|
||||||
"# ending __up_read\n"
|
|
||||||
: "+m"(sem->count), [tmp] "+r" (tmp)
|
|
||||||
: "D"(sem)
|
|
||||||
: "memory", "cc");
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* unlock after writing
|
|
||||||
*/
|
|
||||||
static inline void __up_write(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
unsigned tmp;
|
|
||||||
__asm__ __volatile__(
|
|
||||||
"# beginning __up_write\n\t"
|
|
||||||
" movl %[bias],%[tmp]\n\t"
|
|
||||||
LOCK_PREFIX " xaddl %[tmp],(%%rdi)\n\t" /* tries to transition 0xffff0001 -> 0x00000000 */
|
|
||||||
" jnz 2f\n\t" /* jump if the lock is being waited upon */
|
|
||||||
"1:\n\t"
|
|
||||||
LOCK_SECTION_START("")
|
|
||||||
"2:\n\t"
|
|
||||||
" decw %w[tmp]\n\t" /* did the active count reduce to 0? */
|
|
||||||
" jnz 1b\n\t" /* jump back if not */
|
|
||||||
" call rwsem_wake_thunk\n\t"
|
|
||||||
" jmp 1b\n"
|
|
||||||
LOCK_SECTION_END
|
|
||||||
"# ending __up_write\n"
|
|
||||||
: "+m"(sem->count), [tmp] "=r" (tmp)
|
|
||||||
: "D"(sem), [bias] "i"(-RWSEM_ACTIVE_WRITE_BIAS)
|
|
||||||
: "memory", "cc");
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* downgrade write lock to read lock
|
|
||||||
*/
|
|
||||||
static inline void __downgrade_write(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
__asm__ __volatile__(
|
|
||||||
"# beginning __downgrade_write\n\t"
|
|
||||||
LOCK_PREFIX " addl %[bias],(%%rdi)\n\t" /* transitions 0xZZZZ0001 -> 0xYYYY0001 */
|
|
||||||
" js 2f\n\t" /* jump if the lock is being waited upon */
|
|
||||||
"1:\n\t"
|
|
||||||
LOCK_SECTION_START("")
|
|
||||||
"2:\n\t"
|
|
||||||
" call rwsem_downgrade_thunk\n"
|
|
||||||
" jmp 1b\n"
|
|
||||||
LOCK_SECTION_END
|
|
||||||
"# ending __downgrade_write\n"
|
|
||||||
: "=m"(sem->count)
|
|
||||||
: "D"(sem), [bias] "i"(-RWSEM_WAITING_BIAS), "m"(sem->count)
|
|
||||||
: "memory", "cc");
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* implement atomic add functionality
|
|
||||||
*/
|
|
||||||
static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
__asm__ __volatile__(
|
|
||||||
LOCK_PREFIX "addl %1,%0"
|
|
||||||
:"=m"(sem->count)
|
|
||||||
:"ir"(delta), "m"(sem->count));
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* implement exchange and add functionality
|
|
||||||
*/
|
|
||||||
static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
int tmp = delta;
|
|
||||||
|
|
||||||
__asm__ __volatile__(
|
|
||||||
LOCK_PREFIX "xaddl %0,(%2)"
|
|
||||||
: "=r"(tmp), "=m"(sem->count)
|
|
||||||
: "r"(sem), "m"(sem->count), "0" (tmp)
|
|
||||||
: "memory");
|
|
||||||
|
|
||||||
return tmp+delta;
|
|
||||||
}
|
|
||||||
|
|
||||||
static inline int rwsem_is_locked(struct rw_semaphore *sem)
|
|
||||||
{
|
|
||||||
return (sem->count != 0);
|
|
||||||
}
|
|
||||||
|
|
||||||
#endif /* __KERNEL__ */
|
|
||||||
#endif /* _X8664_RWSEM_H */
|
|
||||||
Loading…
Reference in New Issue