projects / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| fb1c8f93 IM |
1 | #ifndef __LINUX_BIT_SPINLOCK_H |
| 2 | #define __LINUX_BIT_SPINLOCK_H | |
| 3 | ||
| 626d6074 NP |
4 | #include <linux/kernel.h> |
| 5 | #include <linux/preempt.h> | |
| 6 | #include <asm/atomic.h> | |
| 7 | ||
| fb1c8f93 IM |
8 | /* |
| 9 | * bit-based spin_lock() | |
| 10 | * | |
| 11 | * Don't use this unless you really need to: spin_lock() and spin_unlock() | |
| 12 | * are significantly faster. | |
| 13 | */ | |
| 14 | static inline void bit_spin_lock(int bitnum, unsigned long *addr) | |
| 15 | { | |
| 16 | /* | |
| 17 | * Assuming the lock is uncontended, this never enters | |
| 18 | * the body of the outer loop. If it is contended, then | |
| 19 | * within the inner loop a non-atomic test is used to | |
| 20 | * busywait with less bus contention for a good time to | |
| 21 | * attempt to acquire the lock bit. | |
| 22 | */ | |
| 23 | preempt_disable(); | |
| 24 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) | |
| b8dc93cb | 25 | while (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
| fb1c8f93 IM |
26 | while (test_bit(bitnum, addr)) { |
| 27 | preempt_enable(); | |
| 28 | cpu_relax(); | |
| 29 | preempt_disable(); | |
| 30 | } | |
| 31 | } | |
| 32 | #endif | |
| 33 | __acquire(bitlock); | |
| 34 | } | |
| 35 | ||
| 36 | /* | |
| 37 | * Return true if it was acquired | |
| 38 | */ | |
| 39 | static inline int bit_spin_trylock(int bitnum, unsigned long *addr) | |
| 40 | { | |
| 41 | preempt_disable(); | |
| 42 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) | |
| b8dc93cb | 43 | if (unlikely(test_and_set_bit_lock(bitnum, addr))) { |
| fb1c8f93 IM |
44 | preempt_enable(); |
| 45 | return 0; | |
| 46 | } | |
| 47 | #endif | |
| 48 | __acquire(bitlock); | |
| 49 | return 1; | |
| 50 | } | |
| 51 | ||
| 52 | /* | |
| 53 | * bit-based spin_unlock() | |
| 54 | */ | |
| 55 | static inline void bit_spin_unlock(int bitnum, unsigned long *addr) | |
| 56 | { | |
| b8dc93cb NP |
57 | #ifdef CONFIG_DEBUG_SPINLOCK |
| 58 | BUG_ON(!test_bit(bitnum, addr)); | |
| 59 | #endif | |
| fb1c8f93 | 60 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) |
| b8dc93cb NP |
61 | clear_bit_unlock(bitnum, addr); |
| 62 | #endif | |
| 63 | preempt_enable(); | |
| 64 | __release(bitlock); | |
| 65 | } | |
| 66 | ||
| 67 | /* | |
| 68 | * bit-based spin_unlock() | |
| 69 | * non-atomic version, which can be used eg. if the bit lock itself is | |
| 70 | * protecting the rest of the flags in the word. | |
| 71 | */ | |
| 72 | static inline void __bit_spin_unlock(int bitnum, unsigned long *addr) | |
| 73 | { | |
| 74 | #ifdef CONFIG_DEBUG_SPINLOCK | |
| fb1c8f93 | 75 | BUG_ON(!test_bit(bitnum, addr)); |
| b8dc93cb NP |
76 | #endif |
| 77 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) | |
| 78 | __clear_bit_unlock(bitnum, addr); | |
| fb1c8f93 IM |
79 | #endif |
| 80 | preempt_enable(); | |
| 81 | __release(bitlock); | |
| 82 | } | |
| 83 | ||
| 84 | /* | |
| 85 | * Return true if the lock is held. | |
| 86 | */ | |
| 87 | static inline int bit_spin_is_locked(int bitnum, unsigned long *addr) | |
| 88 | { | |
| 89 | #if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) | |
| 90 | return test_bit(bitnum, addr); | |
| 91 | #elif defined CONFIG_PREEMPT | |
| 92 | return preempt_count(); | |
| 93 | #else | |
| 94 | return 1; | |
| 95 | #endif | |
| 96 | } | |
| 97 | ||
| 98 | #endif /* __LINUX_BIT_SPINLOCK_H */ | |
| 99 |