diff options
Diffstat (limited to 'include/asm-x86_64/rwsem.h')
| -rw-r--r-- | include/asm-x86_64/rwsem.h | 283 |
1 files changed, 0 insertions, 283 deletions
diff --git a/include/asm-x86_64/rwsem.h b/include/asm-x86_64/rwsem.h deleted file mode 100644 index 46077e9c1910..000000000000 --- a/include/asm-x86_64/rwsem.h +++ /dev/null @@ -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 */ |