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
  36 #define vcpu_is_preempted vcpu_is_preempted
  37 static inline bool vcpu_is_preempted(long cpu)
  38 {
  39         return pv_vcpu_is_preempted(cpu);
  40 }
  41 #else
  42 static inline void queued_spin_unlock(struct qspinlock *lock)
  43 {
  44         native_queued_spin_unlock(lock);
  45 }
  46 #endif
  47
  48 #ifdef CONFIG_PARAVIRT
  49 #define virt_spin_lock virt_spin_lock
  50 static inline bool virt_spin_lock(struct qspinlock *lock)
  51 {
  52         if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
  53                 return false;
  54
  55         /*
  56          * On hypervisors without PARAVIRT_SPINLOCKS support we fall
  57          * back to a Test-and-Set spinlock, because fair locks have
  58          * horrible lock 'holder' preemption issues.
  59          */
  60
  61         do {
  62                 while (atomic_read(&lock->val) != 0)
  63                         cpu_relax();
  64         } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
  65
  66         return true;
  67 }
  68 #endif /* CONFIG_PARAVIRT */
  69
  70 #include <asm-generic/qspinlock.h>
  71
  72 #endif /* _ASM_X86_QSPINLOCK_H */