diff options
| -rw-r--r-- | kernel/locking/qspinlock_paravirt.h | 24 |
1 files changed, 17 insertions, 7 deletions
diff --git a/kernel/locking/qspinlock_paravirt.h b/kernel/locking/qspinlock_paravirt.h index 4ccfcaae5b89..43555681c40b 100644 --- a/kernel/locking/qspinlock_paravirt.h +++ b/kernel/locking/qspinlock_paravirt.h @@ -72,7 +72,7 @@ static inline bool pv_queued_spin_steal_lock(struct qspinlock *lock) struct __qspinlock *l = (void *)lock; if (!(atomic_read(&lock->val) & _Q_LOCKED_PENDING_MASK) && - (cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0)) { + (cmpxchg_acquire(&l->locked, 0, _Q_LOCKED_VAL) == 0)) { qstat_inc(qstat_pv_lock_stealing, true); return true; } @@ -101,16 +101,16 @@ static __always_inline void clear_pending(struct qspinlock *lock) /* * The pending bit check in pv_queued_spin_steal_lock() isn't a memory - * barrier. Therefore, an atomic cmpxchg() is used to acquire the lock - * just to be sure that it will get it. + * barrier. Therefore, an atomic cmpxchg_acquire() is used to acquire the + * lock just to be sure that it will get it. */ static __always_inline int trylock_clear_pending(struct qspinlock *lock) { struct __qspinlock *l = (void *)lock; return !READ_ONCE(l->locked) && - (cmpxchg(&l->locked_pending, _Q_PENDING_VAL, _Q_LOCKED_VAL) - == _Q_PENDING_VAL); + (cmpxchg_acquire(&l->locked_pending, _Q_PENDING_VAL, + _Q_LOCKED_VAL) == _Q_PENDING_VAL); } #else /* _Q_PENDING_BITS == 8 */ static __always_inline void set_pending(struct qspinlock *lock) @@ -138,7 +138,7 @@ static __always_inline int trylock_clear_pending(struct qspinlock *lock) */ old = val; new = (val & ~_Q_PENDING_MASK) | _Q_LOCKED_VAL; - val = atomic_cmpxchg(&lock->val, old, new); + val = atomic_cmpxchg_acquire(&lock->val, old, new); if (val == old) return 1; @@ -362,8 +362,18 @@ static void pv_kick_node(struct qspinlock *lock, struct mcs_spinlock *node) * observe its next->locked value and advance itself. * * Matches with smp_store_mb() and cmpxchg() in pv_wait_node() + * + * The write to next->locked in arch_mcs_spin_unlock_contended() + * must be ordered before the read of pn->state in the cmpxchg() + * below for the code to work correctly. To guarantee full ordering + * irrespective of the success or failure of the cmpxchg(), + * a relaxed version with explicit barrier is used. The control + * dependency will order the reading of pn->state before any + * subsequent writes. */ - if (cmpxchg(&pn->state, vcpu_halted, vcpu_hashed) != vcpu_halted) + smp_mb__before_atomic(); + if (cmpxchg_relaxed(&pn->state, vcpu_halted, vcpu_hashed) + != vcpu_halted) return; /* |