arch/x86/include/asm/qspinlock.h

   1 #ifndef _ASM_X86_QSPINLOCK_H
   2 #define _ASM_X86_QSPINLOCK_H
   3
   4 #include <asm/cpufeature.h>
   5 #include <asm-generic/qspinlock_types.h>
   6 #include <asm/paravirt.h>
   7
   8 #define queued_spin_unlock queued_spin_unlock
   9 /**
  10  * queued_spin_unlock - release a queued spinlock
  11  * @lock : Pointer to queued spinlock structure
  12  *
  13  * A smp_store_release() on the least-significant byte.
  14  */
  15 static inline void native_queued_spin_unlock(struct qspinlock *lock)
  16 {
  17         smp_store_release((u8 *)lock, 0);
  18 }
  19
  20 #ifdef CONFIG_PARAVIRT_SPINLOCKS
  21 extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
  22 extern void __pv_init_lock_hash(void);
  23 extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
  24 extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
  25
  26 static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
  27 {
  28         pv_queued_spin_lock_slowpath(lock, val);
  29 }
  30
  31 static inline void queued_spin_unlock(struct qspinlock *lock)
  32 {
  33         pv_queued_spin_unlock(lock);
  34 }
  35 #else
  36 static inline void queued_spin_unlock(struct qspinlock *lock)
  37 {
  38         native_queued_spin_unlock(lock);
  39 }
  40 #endif
  41
  42 #ifdef CONFIG_PARAVIRT
  43 #define virt_spin_lock virt_spin_lock
  44 static inline bool virt_spin_lock(struct qspinlock *lock)
  45 {
  46         if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
  47                 return false;
  48
  49         /*
  50          * On hypervisors without PARAVIRT_SPINLOCKS support we fall
  51          * back to a Test-and-Set spinlock, because fair locks have
  52          * horrible lock 'holder' preemption issues.
  53          */
  54
  55         do {
  56                 while (atomic_read(&lock->val) != 0)
  57                         cpu_relax();
  58         } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
  59
  60         return true;
  61 }
  62 #endif /* CONFIG_PARAVIRT */
  63
  64 #include <asm-generic/qspinlock.h>
  65
  66 #endif /* _ASM_X86_QSPINLOCK_H */