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Re: [Xen-devel] [PATCH 10/11] qspinlock: Paravirt support
- To: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>, Waiman.Long@xxxxxx, tglx@xxxxxxxxxxxxx, mingo@xxxxxxxxxx
- From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
- Date: Wed, 18 Jun 2014 14:04:28 +0200
- Cc: linux-arch@xxxxxxxxxxxxxxx, gleb@xxxxxxxxxx, kvm@xxxxxxxxxxxxxxx, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, scott.norton@xxxxxx, raghavendra.kt@xxxxxxxxxxxxxxxxxx, paolo.bonzini@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, chegu_vinod@xxxxxx, david.vrabel@xxxxxxxxxx, oleg@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, boris.ostrovsky@xxxxxxxxxx, paulmck@xxxxxxxxxxxxxxxxxx, torvalds@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 18 Jun 2014 12:05:21 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
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)
{
barrier();
ACCESS_ONCE(*(u8 *)lock) = 0;
}
+#else
+
+static inline void native_queue_unlock(struct qspinlock *lock)
+{
+ atomic_dec(&lock->val);
+}
+
#endif /* !CONFIG_X86_OOSTORE && !CONFIG_X86_PPRO_FENCE */
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.
Paolo
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