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-rw-r--r--include/asm-x86/rwsem.h265
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diff --git a/include/asm-x86/rwsem.h b/include/asm-x86/rwsem.h
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index 3ff3015b71a8..000000000000
--- a/include/asm-x86/rwsem.h
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-/* 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 */