diff options
Diffstat (limited to 'arch/x86/include/asm/spinlock.h')
| -rw-r--r-- | arch/x86/include/asm/spinlock.h | 174 |
1 files changed, 0 insertions, 174 deletions
diff --git a/arch/x86/include/asm/spinlock.h b/arch/x86/include/asm/spinlock.h index be0a05913b91..921bea7a2708 100644 --- a/arch/x86/include/asm/spinlock.h +++ b/arch/x86/include/asm/spinlock.h @@ -20,187 +20,13 @@ * (the type definitions are in asm/spinlock_types.h) */ -#ifdef CONFIG_X86_32 -# define LOCK_PTR_REG "a" -#else -# define LOCK_PTR_REG "D" -#endif - -#if defined(CONFIG_X86_32) && (defined(CONFIG_X86_PPRO_FENCE)) -/* - * On PPro SMP, we use a locked operation to unlock - * (PPro errata 66, 92) - */ -# define UNLOCK_LOCK_PREFIX LOCK_PREFIX -#else -# define UNLOCK_LOCK_PREFIX -#endif - /* How long a lock should spin before we consider blocking */ #define SPIN_THRESHOLD (1 << 15) extern struct static_key paravirt_ticketlocks_enabled; static __always_inline bool static_key_false(struct static_key *key); -#ifdef CONFIG_QUEUED_SPINLOCKS #include <asm/qspinlock.h> -#else - -#ifdef CONFIG_PARAVIRT_SPINLOCKS - -static inline void __ticket_enter_slowpath(arch_spinlock_t *lock) -{ - set_bit(0, (volatile unsigned long *)&lock->tickets.head); -} - -#else /* !CONFIG_PARAVIRT_SPINLOCKS */ -static __always_inline void __ticket_lock_spinning(arch_spinlock_t *lock, - __ticket_t ticket) -{ -} -static inline void __ticket_unlock_kick(arch_spinlock_t *lock, - __ticket_t ticket) -{ -} - -#endif /* CONFIG_PARAVIRT_SPINLOCKS */ -static inline int __tickets_equal(__ticket_t one, __ticket_t two) -{ - return !((one ^ two) & ~TICKET_SLOWPATH_FLAG); -} - -static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock, - __ticket_t head) -{ - if (head & TICKET_SLOWPATH_FLAG) { - arch_spinlock_t old, new; - - old.tickets.head = head; - new.tickets.head = head & ~TICKET_SLOWPATH_FLAG; - old.tickets.tail = new.tickets.head + TICKET_LOCK_INC; - new.tickets.tail = old.tickets.tail; - - /* try to clear slowpath flag when there are no contenders */ - cmpxchg(&lock->head_tail, old.head_tail, new.head_tail); - } -} - -static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock) -{ - return __tickets_equal(lock.tickets.head, lock.tickets.tail); -} - -/* - * Ticket locks are conceptually two parts, one indicating the current head of - * the queue, and the other indicating the current tail. The lock is acquired - * by atomically noting the tail and incrementing it by one (thus adding - * ourself to the queue and noting our position), then waiting until the head - * becomes equal to the the initial value of the tail. - * - * We use an xadd covering *both* parts of the lock, to increment the tail and - * also load the position of the head, which takes care of memory ordering - * issues and should be optimal for the uncontended case. Note the tail must be - * in the high part, because a wide xadd increment of the low part would carry - * up and contaminate the high part. - */ -static __always_inline void arch_spin_lock(arch_spinlock_t *lock) -{ - register struct __raw_tickets inc = { .tail = TICKET_LOCK_INC }; - - inc = xadd(&lock->tickets, inc); - if (likely(inc.head == inc.tail)) - goto out; - - for (;;) { - unsigned count = SPIN_THRESHOLD; - - do { - inc.head = READ_ONCE(lock->tickets.head); - if (__tickets_equal(inc.head, inc.tail)) - goto clear_slowpath; - cpu_relax(); - } while (--count); - __ticket_lock_spinning(lock, inc.tail); - } -clear_slowpath: - __ticket_check_and_clear_slowpath(lock, inc.head); -out: - barrier(); /* make sure nothing creeps before the lock is taken */ -} - -static __always_inline int arch_spin_trylock(arch_spinlock_t *lock) -{ - arch_spinlock_t old, new; - - old.tickets = READ_ONCE(lock->tickets); - if (!__tickets_equal(old.tickets.head, old.tickets.tail)) - return 0; - - new.head_tail = old.head_tail + (TICKET_LOCK_INC << TICKET_SHIFT); - new.head_tail &= ~TICKET_SLOWPATH_FLAG; - - /* cmpxchg is a full barrier, so nothing can move before it */ - return cmpxchg(&lock->head_tail, old.head_tail, new.head_tail) == old.head_tail; -} - -static __always_inline void arch_spin_unlock(arch_spinlock_t *lock) -{ - if (TICKET_SLOWPATH_FLAG && - static_key_false(¶virt_ticketlocks_enabled)) { - __ticket_t head; - - BUILD_BUG_ON(((__ticket_t)NR_CPUS) != NR_CPUS); - - head = xadd(&lock->tickets.head, TICKET_LOCK_INC); - - if (unlikely(head & TICKET_SLOWPATH_FLAG)) { - head &= ~TICKET_SLOWPATH_FLAG; - __ticket_unlock_kick(lock, (head + TICKET_LOCK_INC)); - } - } else - __add(&lock->tickets.head, TICKET_LOCK_INC, UNLOCK_LOCK_PREFIX); -} - -static inline int arch_spin_is_locked(arch_spinlock_t *lock) -{ - struct __raw_tickets tmp = READ_ONCE(lock->tickets); - - return !__tickets_equal(tmp.tail, tmp.head); -} - -static inline int arch_spin_is_contended(arch_spinlock_t *lock) -{ - struct __raw_tickets tmp = READ_ONCE(lock->tickets); - - tmp.head &= ~TICKET_SLOWPATH_FLAG; - return (__ticket_t)(tmp.tail - tmp.head) > TICKET_LOCK_INC; -} -#define arch_spin_is_contended arch_spin_is_contended - -static __always_inline void arch_spin_lock_flags(arch_spinlock_t *lock, - unsigned long flags) -{ - arch_spin_lock(lock); -} - -static inline void arch_spin_unlock_wait(arch_spinlock_t *lock) -{ - __ticket_t head = READ_ONCE(lock->tickets.head); - - for (;;) { - struct __raw_tickets tmp = READ_ONCE(lock->tickets); - /* - * We need to check "unlocked" in a loop, tmp.head == head - * can be false positive because of overflow. - */ - if (__tickets_equal(tmp.head, tmp.tail) || - !__tickets_equal(tmp.head, head)) - break; - - cpu_relax(); - } -} -#endif /* CONFIG_QUEUED_SPINLOCKS */ /* * Read-write spinlocks, allowing multiple readers |