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Diffstat (limited to 'arch/tile/include/asm/spinlock_32.h')
| -rw-r--r-- | arch/tile/include/asm/spinlock_32.h | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/arch/tile/include/asm/spinlock_32.h b/arch/tile/include/asm/spinlock_32.h new file mode 100644 index 0000000..88efdde8 --- /dev/null +++ b/arch/tile/include/asm/spinlock_32.h @@ -0,0 +1,199 @@ +/* + * Copyright 2010 Tilera Corporation. All Rights Reserved. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation, version 2. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or + * NON INFRINGEMENT. See the GNU General Public License for + * more details. + * + * 32-bit SMP spinlocks. + */ + +#ifndef _ASM_TILE_SPINLOCK_32_H +#define _ASM_TILE_SPINLOCK_32_H + +#include <asm/atomic.h> +#include <asm/page.h> +#include <asm/system.h> +#include <linux/compiler.h> + +/* + * We only use even ticket numbers so the '1' inserted by a tns is + * an unambiguous "ticket is busy" flag. + */ +#define TICKET_QUANTUM 2 + + +/* + * SMP ticket spinlocks, allowing only a single CPU anywhere + * + * (the type definitions are in asm/spinlock_types.h) + */ +static inline int arch_spin_is_locked(arch_spinlock_t *lock) +{ + /* + * Note that even if a new ticket is in the process of being + * acquired, so lock->next_ticket is 1, it's still reasonable + * to claim the lock is held, since it will be momentarily + * if not already. There's no need to wait for a "valid" + * lock->next_ticket to become available. + */ + return lock->next_ticket != lock->current_ticket; +} + +void arch_spin_lock(arch_spinlock_t *lock); + +/* We cannot take an interrupt after getting a ticket, so don't enable them. */ +#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock) + +int arch_spin_trylock(arch_spinlock_t *lock); + +static inline void arch_spin_unlock(arch_spinlock_t *lock) +{ + /* For efficiency, overlap fetching the old ticket with the wmb(). */ + int old_ticket = lock->current_ticket; + wmb(); /* guarantee anything modified under the lock is visible */ + lock->current_ticket = old_ticket + TICKET_QUANTUM; +} + +void arch_spin_unlock_wait(arch_spinlock_t *lock); + +/* + * Read-write spinlocks, allowing multiple readers + * but only one writer. + * + * We use a "tns/store-back" technique on a single word to manage + * the lock state, looping around to retry if the tns returns 1. + */ + +/* Internal layout of the word; do not use. */ +#define _WR_NEXT_SHIFT 8 +#define _WR_CURR_SHIFT 16 +#define _WR_WIDTH 8 +#define _RD_COUNT_SHIFT 24 +#define _RD_COUNT_WIDTH 8 + +/* Internal functions; do not use. */ +void arch_read_lock_slow(arch_rwlock_t *, u32); +int arch_read_trylock_slow(arch_rwlock_t *); +void arch_read_unlock_slow(arch_rwlock_t *); +void arch_write_lock_slow(arch_rwlock_t *, u32); +void arch_write_unlock_slow(arch_rwlock_t *, u32); + +/** + * arch_read_can_lock() - would read_trylock() succeed? + */ +static inline int arch_read_can_lock(arch_rwlock_t *rwlock) +{ + return (rwlock->lock << _RD_COUNT_WIDTH) == 0; +} + +/** + * arch_write_can_lock() - would write_trylock() succeed? + */ +static inline int arch_write_can_lock(arch_rwlock_t *rwlock) +{ + return rwlock->lock == 0; +} + +/** + * arch_read_lock() - acquire a read lock. + */ +static inline void arch_read_lock(arch_rwlock_t *rwlock) +{ + u32 val = __insn_tns((int *)&rwlock->lock); + if (unlikely(val << _RD_COUNT_WIDTH)) { + arch_read_lock_slow(rwlock, val); + return; + } + rwlock->lock = val + (1 << _RD_COUNT_SHIFT); +} + +/** + * arch_read_lock() - acquire a write lock. + */ +static inline void arch_write_lock(arch_rwlock_t *rwlock) +{ + u32 val = __insn_tns((int *)&rwlock->lock); + if (unlikely(val != 0)) { + arch_write_lock_slow(rwlock, val); + return; + } + rwlock->lock = 1 << _WR_NEXT_SHIFT; +} + +/** + * arch_read_trylock() - try to acquire a read lock. + */ +static inline int arch_read_trylock(arch_rwlock_t *rwlock) +{ + int locked; + u32 val = __insn_tns((int *)&rwlock->lock); + if (unlikely(val & 1)) + return arch_read_trylock_slow(rwlock); + locked = (val << _RD_COUNT_WIDTH) == 0; + rwlock->lock = val + (locked << _RD_COUNT_SHIFT); + return locked; +} + +/** + * arch_write_trylock() - try to acquire a write lock. + */ +static inline int arch_write_trylock(arch_rwlock_t *rwlock) +{ + u32 val = __insn_tns((int *)&rwlock->lock); + + /* + * If a tns is in progress, or there's a waiting or active locker, + * or active readers, we can't take the lock, so give up. + */ + if (unlikely(val != 0)) { + if (!(val & 1)) + rwlock->lock = val; + return 0; + } + + /* Set the "next" field to mark it locked. */ + rwlock->lock = 1 << _WR_NEXT_SHIFT; + return 1; +} + +/** + * arch_read_unlock() - release a read lock. + */ +static inline void arch_read_unlock(arch_rwlock_t *rwlock) +{ + u32 val; + mb(); /* guarantee anything modified under the lock is visible */ + val = __insn_tns((int *)&rwlock->lock); + if (unlikely(val & 1)) { + arch_read_unlock_slow(rwlock); + return; + } + rwlock->lock = val - (1 << _RD_COUNT_SHIFT); +} + +/** + * arch_write_unlock() - release a write lock. + */ +static inline void arch_write_unlock(arch_rwlock_t *rwlock) +{ + u32 val; + mb(); /* guarantee anything modified under the lock is visible */ + val = __insn_tns((int *)&rwlock->lock); + if (unlikely(val != (1 << _WR_NEXT_SHIFT))) { + arch_write_unlock_slow(rwlock, val); + return; + } + rwlock->lock = 0; +} + +#define arch_read_lock_flags(lock, flags) arch_read_lock(lock) +#define arch_write_lock_flags(lock, flags) arch_write_lock(lock) + +#endif /* _ASM_TILE_SPINLOCK_32_H */ |
