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Re: [Xen-devel] [PATCH 10/11] qspinlock: Paravirt support

Il 15/06/2014 14:47, Peter Zijlstra ha scritto:

 #if !defined(CONFIG_X86_OOSTORE) && !defined(CONFIG_X86_PPRO_FENCE)

-#define        queue_spin_unlock queue_spin_unlock
  * queue_spin_unlock - release a queue spinlock
  * @lock : Pointer to queue spinlock structure
  * An effective smp_store_release() on the least-significant byte.
-static inline void queue_spin_unlock(struct qspinlock *lock)
+static inline void native_queue_unlock(struct qspinlock *lock)
        ACCESS_ONCE(*(u8 *)lock) = 0;

+static inline void native_queue_unlock(struct qspinlock *lock)
+       atomic_dec(&lock->val);

Should be (part of) an earlier patch? Also, does it get wrong if (CONFIG_X86_OOSTORE || CONFIG_X86_PPRO_FENCE) && paravirt patches the unlock to a single movb? Of course the paravirt spinlocks could simply depend on !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE.

+#define INVALID_HEAD   -1
+#define NO_HEAD                nr_cpu_ids

-2, like Waiman said.


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