| #ifndef __LINUX_BIT_SPINLOCK_H |
| #define __LINUX_BIT_SPINLOCK_H |
| |
| #include <linux/kernel.h> |
| #include <linux/preempt.h> |
| #include <asm/atomic.h> |
| |
| /* |
| * bit-based spin_lock() |
| * |
| * Don't use this unless you really need to: spin_lock() and spin_unlock() |
| * are significantly faster. |
| */ |
| static inline void bit_spin_lock(int bitnum, unsigned long *addr) |
| { |
| /* |
| * Assuming the lock is uncontended, this never enters |
| * the body of the outer loop. If it is contended, then |
| * within the inner loop a non-atomic test is used to |
| * busywait with less bus contention for a good time to |
| * attempt to acquire the lock bit. |
| */ |
| preempt_disable(); |
| #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
| while (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
| preempt_enable(); |
| do { |
| cpu_relax(); |
| } while (test_bit(bitnum, addr)); |
| preempt_disable(); |
| } |
| #endif |
| __acquire(bitlock); |
| } |
| |
| /* |
| * Return true if it was acquired |
| */ |
| static inline int bit_spin_trylock(int bitnum, unsigned long *addr) |
| { |
| preempt_disable(); |
| #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
| if (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
| preempt_enable(); |
| return 0; |
| } |
| #endif |
| __acquire(bitlock); |
| return 1; |
| } |
| |
| /* |
| * bit-based spin_unlock() |
| */ |
| static inline void bit_spin_unlock(int bitnum, unsigned long *addr) |
| { |
| #ifdef CONFIG_DEBUG_SPINLOCK |
| BUG_ON(!test_bit(bitnum, addr)); |
| #endif |
| #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
| clear_bit_unlock(bitnum, addr); |
| #endif |
| preempt_enable(); |
| __release(bitlock); |
| } |
| |
| /* |
| * bit-based spin_unlock() |
| * non-atomic version, which can be used eg. if the bit lock itself is |
| * protecting the rest of the flags in the word. |
| */ |
| static inline void __bit_spin_unlock(int bitnum, unsigned long *addr) |
| { |
| #ifdef CONFIG_DEBUG_SPINLOCK |
| BUG_ON(!test_bit(bitnum, addr)); |
| #endif |
| #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
| __clear_bit_unlock(bitnum, addr); |
| #endif |
| preempt_enable(); |
| __release(bitlock); |
| } |
| |
| /* |
| * Return true if the lock is held. |
| */ |
| static inline int bit_spin_is_locked(int bitnum, unsigned long *addr) |
| { |
| #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
| return test_bit(bitnum, addr); |
| #elif defined CONFIG_PREEMPT_COUNT |
| return preempt_count(); |
| #else |
| return 1; |
| #endif |
| } |
| |
| #endif /* __LINUX_BIT_SPINLOCK_H */ |
| |