arch/x86/include/asm/qspinlock.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_X86_QSPINLOCK_H
   3 #define _ASM_X86_QSPINLOCK_H
   4
   5 #include <linux/jump_label.h>
   6 #include <asm/cpufeature.h>
   7 #include <asm-generic/qspinlock_types.h>
   8 #include <asm/paravirt.h>
   9 #include <asm/rmwcc.h>
  10
  11 #define _Q_PENDING_LOOPS        (1 << 9)
  12
  13 #define queued_fetch_set_pending_acquire queued_fetch_set_pending_acquire
  14 static __always_inline u32 queued_fetch_set_pending_acquire(struct qspinlock *lock)
  15 {
  16         u32 val;
  17
  18         /*
  19          * We can't use GEN_BINARY_RMWcc() inside an if() stmt because asm goto
  20          * and CONFIG_PROFILE_ALL_BRANCHES=y results in a label inside a
  21          * statement expression, which GCC doesn't like.
  22          */
  23         val = GEN_BINARY_RMWcc(LOCK_PREFIX "btsl", lock->val.counter, c,
  24                                "I", _Q_PENDING_OFFSET) * _Q_PENDING_VAL;
  25         val |= atomic_read(&lock->val) & ~_Q_PENDING_MASK;
  26
  27         return val;
  28 }
  29
  30 #ifdef CONFIG_PARAVIRT_SPINLOCKS
  31 extern void native_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
  32 extern void __pv_init_lock_hash(void);
  33 extern void __pv_queued_spin_lock_slowpath(struct qspinlock *lock, u32 val);
  34 extern void __raw_callee_save___pv_queued_spin_unlock(struct qspinlock *lock);
  35
  36 #define queued_spin_unlock queued_spin_unlock
  37 /**
  38  * queued_spin_unlock - release a queued spinlock
  39  * @lock : Pointer to queued spinlock structure
  40  *
  41  * A smp_store_release() on the least-significant byte.
  42  */
  43 static inline void native_queued_spin_unlock(struct qspinlock *lock)
  44 {
  45         smp_store_release(&lock->locked, 0);
  46 }
  47
  48 static inline void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
  49 {
  50         pv_queued_spin_lock_slowpath(lock, val);
  51 }
  52
  53 static inline void queued_spin_unlock(struct qspinlock *lock)
  54 {
  55         pv_queued_spin_unlock(lock);
  56 }
  57
  58 #define vcpu_is_preempted vcpu_is_preempted
  59 static inline bool vcpu_is_preempted(long cpu)
  60 {
  61         return pv_vcpu_is_preempted(cpu);
  62 }
  63 #endif
  64
  65 #ifdef CONFIG_PARAVIRT
  66 DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key);
  67
  68 void native_pv_lock_init(void) __init;
  69
  70 #define virt_spin_lock virt_spin_lock
  71 static inline bool virt_spin_lock(struct qspinlock *lock)
  72 {
  73         if (!static_branch_likely(&virt_spin_lock_key))
  74                 return false;
  75
  76         /*
  77          * On hypervisors without PARAVIRT_SPINLOCKS support we fall
  78          * back to a Test-and-Set spinlock, because fair locks have
  79          * horrible lock 'holder' preemption issues.
  80          */
  81
  82         do {
  83                 while (atomic_read(&lock->val) != 0)
  84                         cpu_relax();
  85         } while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0);
  86
  87         return true;
  88 }
  89 #else
  90 static inline void native_pv_lock_init(void)
  91 {
  92 }
  93 #endif /* CONFIG_PARAVIRT */
  94
  95 #include <asm-generic/qspinlock.h>
  96
  97 #endif /* _ASM_X86_QSPINLOCK_H */