xen/irq: Alter the locking to use a mutex instead of a spinlock.

When we allocate/change the IRQ informations, we do not
need to use spinlocks. We can use a mutex (which is
what the generic IRQ code does for allocations/changes).
Fixes a slew of:

BUG: sleeping function called from invalid context at /linux/kernel/mutex.c:271
in_atomic(): 1, irqs_disabled(): 0, pid: 3216, name: xenstored
2 locks held by xenstored/3216:
 #0:  (&u->bind_mutex){......}, at: [<ffffffffa02e0920>] evtchn_ioctl+0x30/0x3a0 [xen_evtchn]
 #1:  (irq_mapping_update_lock){......}, at: [<ffffffff8138b274>] bind_evtchn_to_irq+0x24/0x90
Pid: 3216, comm: xenstored Not tainted 3.1.0-rc6-00021-g437a3d1 #2
Call Trace:
 [<ffffffff81088d10>] __might_sleep+0x100/0x130
 [<ffffffff81645c2f>] mutex_lock_nested+0x2f/0x50
 [<ffffffff81627529>] __irq_alloc_descs+0x49/0x200
 [<ffffffffa02e0920>] ? evtchn_ioctl+0x30/0x3a0 [xen_evtchn]
 [<ffffffff8138b214>] xen_allocate_irq_dynamic+0x34/0x70
 [<ffffffff8138b2ad>] bind_evtchn_to_irq+0x5d/0x90
 [<ffffffffa02e03c0>] ? evtchn_bind_to_user+0x60/0x60 [xen_evtchn]
 [<ffffffff8138c282>] bind_evtchn_to_irqhandler+0x32/0x80
 [<ffffffffa02e03a9>] evtchn_bind_to_user+0x49/0x60 [xen_evtchn]
 [<ffffffffa02e0a34>] evtchn_ioctl+0x144/0x3a0 [xen_evtchn]
 [<ffffffff811b4070>] ? vfsmount_lock_local_unlock+0x50/0x80
 [<ffffffff811a6a1a>] do_vfs_ioctl+0x9a/0x5e0
 [<ffffffff811b476f>] ? mntput+0x1f/0x30
 [<ffffffff81196259>] ? fput+0x199/0x240
 [<ffffffff811a7001>] sys_ioctl+0xa1/0xb0
 [<ffffffff8164ea82>] system_call_fastpath+0x16/0x1b
Reported-by: Jim Burns <jim_burn@bellsouth.net>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/xen/events.c

@@ -54,7 +54,7 @@
  * This lock protects updates to the following mapping and reference-count
  * arrays. The lock does not need to be acquired to read the mapping tables.
  */
-static DEFINE_SPINLOCK(irq_mapping_update_lock);
+static DEFINE_MUTEX(irq_mapping_update_lock);
 
 static LIST_HEAD(xen_irq_list_head);
 
@@ -631,7 +631,7 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
 	int irq = -1;
 	struct physdev_irq irq_op;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = find_irq_by_gsi(gsi);
 	if (irq != -1) {
@@ -684,7 +684,7 @@ int xen_bind_pirq_gsi_to_irq(unsigned gsi,
 				handle_edge_irq, name);
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -710,7 +710,7 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
 {
 	int irq, ret;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = xen_allocate_irq_dynamic();
 	if (irq == -1)
@@ -724,10 +724,10 @@ int xen_bind_pirq_msi_to_irq(struct pci_dev *dev, struct msi_desc *msidesc,
 	if (ret < 0)
 		goto error_irq;
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	return irq;
 error_irq:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	xen_free_irq(irq);
 	return -1;
 }
@@ -740,7 +740,7 @@ int xen_destroy_irq(int irq)
 	struct irq_info *info = info_for_irq(irq);
 	int rc = -ENOENT;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	desc = irq_to_desc(irq);
 	if (!desc)
@@ -766,7 +766,7 @@ int xen_destroy_irq(int irq)
 	xen_free_irq(irq);
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	return rc;
 }
 
@@ -776,7 +776,7 @@ int xen_irq_from_pirq(unsigned pirq)
 
 	struct irq_info *info;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	list_for_each_entry(info, &xen_irq_list_head, list) {
 		if (info == NULL || info->type != IRQT_PIRQ)
@@ -787,7 +787,7 @@ int xen_irq_from_pirq(unsigned pirq)
 	}
 	irq = -1;
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -802,7 +802,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
 {
 	int irq;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = evtchn_to_irq[evtchn];
 
@@ -818,7 +818,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
 	}
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -829,7 +829,7 @@ static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
 	struct evtchn_bind_ipi bind_ipi;
 	int evtchn, irq;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = per_cpu(ipi_to_irq, cpu)[ipi];
 
@@ -853,7 +853,7 @@ static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
 	}
 
  out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 	return irq;
 }
 
@@ -878,7 +878,7 @@ int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
 	struct evtchn_bind_virq bind_virq;
 	int evtchn, irq;
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	irq = per_cpu(virq_to_irq, cpu)[virq];
 
@@ -903,7 +903,7 @@ int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
 	}
 
 out:
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	return irq;
 }
@@ -913,7 +913,7 @@ static void unbind_from_irq(unsigned int irq)
 	struct evtchn_close close;
 	int evtchn = evtchn_from_irq(irq);
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	if (VALID_EVTCHN(evtchn)) {
 		close.port = evtchn;
@@ -943,7 +943,7 @@ static void unbind_from_irq(unsigned int irq)
 
 	xen_free_irq(irq);
 
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 }
 
 int bind_evtchn_to_irqhandler(unsigned int evtchn,
@@ -1279,7 +1279,7 @@ void rebind_evtchn_irq(int evtchn, int irq)
 	   will also be masked. */
 	disable_irq(irq);
 
-	spin_lock(&irq_mapping_update_lock);
+	mutex_lock(&irq_mapping_update_lock);
 
 	/* After resume the irq<->evtchn mappings are all cleared out */
 	BUG_ON(evtchn_to_irq[evtchn] != -1);
@@ -1289,7 +1289,7 @@ void rebind_evtchn_irq(int evtchn, int irq)
 
 	xen_irq_info_evtchn_init(irq, evtchn);
 
-	spin_unlock(&irq_mapping_update_lock);
+	mutex_unlock(&irq_mapping_update_lock);
 
 	/* new event channels are always bound to cpu 0 */
 	irq_set_affinity(irq, cpumask_of(0));