include/linux/bit_spinlock.h

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