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Diffstat (limited to 'include/asm-x86/rwsem.h')
| -rw-r--r-- | include/asm-x86/rwsem.h | 265 |
1 files changed, 0 insertions, 265 deletions
diff --git a/include/asm-x86/rwsem.h b/include/asm-x86/rwsem.h deleted file mode 100644 index 3ff3015b71a..00000000000 --- a/include/asm-x86/rwsem.h +++ /dev/null @@ -1,265 +0,0 @@ -/* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for i486+ - * - * Written by David Howells (dhowells@redhat.com). - * - * Derived from asm-x86/semaphore.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 consequtive readers at the - * front, then they'll all be woken up, but no other readers will be. - */ - -#ifndef ASM_X86__RWSEM_H -#define ASM_X86__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> -#include <linux/lockdep.h> - -struct rwsem_waiter; - -extern asmregparm struct rw_semaphore * - rwsem_down_read_failed(struct rw_semaphore *sem); -extern asmregparm struct rw_semaphore * - rwsem_down_write_failed(struct rw_semaphore *sem); -extern asmregparm struct rw_semaphore * - rwsem_wake(struct rw_semaphore *); -extern asmregparm struct rw_semaphore * - rwsem_downgrade_wake(struct rw_semaphore *sem); - -/* - * the semaphore definition - */ - -#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) - -struct rw_semaphore { - signed long count; - spinlock_t wait_lock; - struct list_head wait_list; -#ifdef CONFIG_DEBUG_LOCK_ALLOC - struct lockdep_map dep_map; -#endif -}; - -#ifdef CONFIG_DEBUG_LOCK_ALLOC -# define __RWSEM_DEP_MAP_INIT(lockname) , .dep_map = { .name = #lockname } -#else -# define __RWSEM_DEP_MAP_INIT(lockname) -#endif - - -#define __RWSEM_INITIALIZER(name) \ -{ \ - RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED((name).wait_lock), \ - LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) \ -} - -#define DECLARE_RWSEM(name) \ - struct rw_semaphore name = __RWSEM_INITIALIZER(name) - -extern void __init_rwsem(struct rw_semaphore *sem, const char *name, - struct lock_class_key *key); - -#define init_rwsem(sem) \ -do { \ - static struct lock_class_key __key; \ - \ - __init_rwsem((sem), #sem, &__key); \ -} while (0) - -/* - * lock for reading - */ -static inline void __down_read(struct rw_semaphore *sem) -{ - asm volatile("# beginning down_read\n\t" - LOCK_PREFIX " incl (%%eax)\n\t" - /* adds 0x00000001, returns the old value */ - " jns 1f\n" - " call call_rwsem_down_read_failed\n" - "1:\n\t" - "# ending down_read\n\t" - : "+m" (sem->count) - : "a" (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_nested(struct rw_semaphore *sem, int subclass) -{ - int tmp; - - tmp = RWSEM_ACTIVE_WRITE_BIAS; - asm volatile("# beginning down_write\n\t" - LOCK_PREFIX " xadd %%edx,(%%eax)\n\t" - /* subtract 0x0000ffff, returns the old value */ - " testl %%edx,%%edx\n\t" - /* was the count 0 before? */ - " jz 1f\n" - " call call_rwsem_down_write_failed\n" - "1:\n" - "# ending down_write" - : "+m" (sem->count), "=d" (tmp) - : "a" (sem), "1" (tmp) - : "memory", "cc"); -} - -static inline void __down_write(struct rw_semaphore *sem) -{ - __down_write_nested(sem, 0); -} - -/* - * 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 " xadd %%edx,(%%eax)\n\t" - /* subtracts 1, returns the old value */ - " jns 1f\n\t" - " call call_rwsem_wake\n" - "1:\n" - "# ending __up_read\n" - : "+m" (sem->count), "=d" (tmp) - : "a" (sem), "1" (tmp) - : "memory", "cc"); -} - -/* - * unlock after writing - */ -static inline void __up_write(struct rw_semaphore *sem) -{ - asm volatile("# beginning __up_write\n\t" - " movl %2,%%edx\n\t" - LOCK_PREFIX " xaddl %%edx,(%%eax)\n\t" - /* tries to transition - 0xffff0001 -> 0x00000000 */ - " jz 1f\n" - " call call_rwsem_wake\n" - "1:\n\t" - "# ending __up_write\n" - : "+m" (sem->count) - : "a" (sem), "i" (-RWSEM_ACTIVE_WRITE_BIAS) - : "memory", "cc", "edx"); -} - -/* - * 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 %2,(%%eax)\n\t" - /* transitions 0xZZZZ0001 -> 0xYYYY0001 */ - " jns 1f\n\t" - " call call_rwsem_downgrade_wake\n" - "1:\n\t" - "# ending __downgrade_write\n" - : "+m" (sem->count) - : "a" (sem), "i" (-RWSEM_WAITING_BIAS) - : "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)); -} - -/* - * implement exchange and add functionality - */ -static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem) -{ - int tmp = delta; - - asm volatile(LOCK_PREFIX "xadd %0,%1" - : "+r" (tmp), "+m" (sem->count) - : : "memory"); - - return tmp + delta; -} - -static inline int rwsem_is_locked(struct rw_semaphore *sem) -{ - return (sem->count != 0); -} - -#endif /* __KERNEL__ */ -#endif /* ASM_X86__RWSEM_H */ |