This lock is only intended to prevent racing with closing an event
channel - evtchn_set_pending() doesn't require external serialization.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -147,7 +147,7 @@ struct vcpu *alloc_vcpu(
v->domain = d;
v->vcpu_id = vcpu_id;
- spin_lock_init(&v->virq_lock);
+ rwlock_init(&v->virq_lock);
tasklet_init(&v->continue_hypercall_tasklet, NULL, 0);
--- a/xen/common/event_channel.c
+++ b/xen/common/event_channel.c
@@ -417,7 +417,7 @@ static long __evtchn_close(struct domain
if ( v->virq_to_evtchn[chn1->u.virq] != port1 )
continue;
v->virq_to_evtchn[chn1->u.virq] = 0;
- spin_barrier_irq(&v->virq_lock);
+ write_barrier_irq(&v->virq_lock);
}
break;
@@ -613,12 +613,11 @@ int guest_enabled_event(struct vcpu *v,
void send_guest_vcpu_virq(struct vcpu *v, int virq)
{
- unsigned long flags;
int port;
ASSERT(!virq_is_global(virq));
- spin_lock_irqsave(&v->virq_lock, flags);
+ read_lock(&v->virq_lock);
port = v->virq_to_evtchn[virq];
if ( unlikely(port == 0) )
@@ -627,12 +626,11 @@ void send_guest_vcpu_virq(struct vcpu *v
evtchn_set_pending(v, port);
out:
- spin_unlock_irqrestore(&v->virq_lock, flags);
+ read_unlock(&v->virq_lock);
}
void send_guest_global_virq(struct domain *d, int virq)
{
- unsigned long flags;
int port;
struct vcpu *v;
struct evtchn *chn;
@@ -646,7 +644,7 @@ void send_guest_global_virq(struct domai
if ( unlikely(v == NULL) )
return;
- spin_lock_irqsave(&v->virq_lock, flags);
+ read_lock(&v->virq_lock);
port = v->virq_to_evtchn[virq];
if ( unlikely(port == 0) )
@@ -656,7 +654,7 @@ void send_guest_global_virq(struct domai
evtchn_set_pending(d->vcpu[chn->notify_vcpu_id], port);
out:
- spin_unlock_irqrestore(&v->virq_lock, flags);
+ read_unlock(&v->virq_lock);
}
int send_guest_pirq(struct domain *d, int pirq)
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -344,6 +344,20 @@ int _rw_is_write_locked(rwlock_t *lock)
return _raw_rw_is_write_locked(&lock->raw);
}
+void _write_barrier(rwlock_t *lock)
+{
+ check_lock(&lock->debug);
+ do { mb(); } while ( _raw_rw_is_locked(&lock->raw) );
+}
+
+void _write_barrier_irq(rwlock_t *lock)
+{
+ unsigned long flags;
+ local_irq_save(flags);
+ _write_barrier(lock);
+ local_irq_restore(flags);
+}
+
#ifdef LOCK_PROFILE
struct lock_profile_anc {
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -157,9 +157,12 @@ struct vcpu
unsigned long pause_flags;
atomic_t pause_count;
- /* IRQ-safe virq_lock protects against delivering VIRQ to stale evtchn. */
+ /*
+ * Writer-side-IRQ-safe virq_lock protects against delivering VIRQ
+ * to stale evtchn.
+ */
u16 virq_to_evtchn[NR_VIRQS];
- spinlock_t virq_lock;
+ rwlock_t virq_lock;
/* Bitmask of CPUs on which this VCPU may run. */
cpumask_t cpu_affinity;
--- a/xen/include/xen/spinlock.h
+++ b/xen/include/xen/spinlock.h
@@ -170,6 +170,9 @@ void _write_unlock_irqrestore(rwlock_t *
int _rw_is_locked(rwlock_t *lock);
int _rw_is_write_locked(rwlock_t *lock);
+void _write_barrier(rwlock_t *lock);
+void _write_barrier_irq(rwlock_t *lock);
+
#define spin_lock(l) _spin_lock(l)
#define spin_lock_irq(l) _spin_lock_irq(l)
#define spin_lock_irqsave(l, f) ((f) = _spin_lock_irqsave(l))
@@ -223,4 +226,7 @@ int _rw_is_write_locked(rwlock_t *lock);
#define rw_is_locked(l) _rw_is_locked(l)
#define rw_is_write_locked(l) _rw_is_write_locked(l)
+#define write_barrier(l) _write_barrier(l)
+#define write_barrier_irq(l) _write_barrier_irq(l)
+
#endif /* __SPINLOCK_H__ */
virq-rwlock.patch
Description: Text document
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