arch/loongarch/include/asm/qspinlock.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_LOONGARCH_QSPINLOCK_H
   3 #define _ASM_LOONGARCH_QSPINLOCK_H
   4
   5 #include <linux/jump_label.h>
   6
   7 #ifdef CONFIG_PARAVIRT
   8
   9 DECLARE_STATIC_KEY_FALSE(virt_spin_lock_key);
  10
  11 #define virt_spin_lock virt_spin_lock
  12
  13 static inline bool virt_spin_lock(struct qspinlock *lock)
  14 {
  15         int val;
  16
  17         if (!static_branch_unlikely(&virt_spin_lock_key))
  18                 return false;
  19
  20         /*
  21          * On hypervisors without PARAVIRT_SPINLOCKS support we fall
  22          * back to a Test-and-Set spinlock, because fair locks have
  23          * horrible lock 'holder' preemption issues.
  24          */
  25
  26 __retry:
  27         val = atomic_read(&lock->val);
  28
  29         if (val || !atomic_try_cmpxchg(&lock->val, &val, _Q_LOCKED_VAL)) {
  30                 cpu_relax();
  31                 goto __retry;
  32         }
  33
  34         return true;
  35 }
  36
  37 #endif /* CONFIG_PARAVIRT */
  38
  39 #include <asm-generic/qspinlock.h>
  40
  41 #endif // _ASM_LOONGARCH_QSPINLOCK_H