diff -r 1020c52c58c1 -r ba12bfbe2f5c linux-2.6-xen-sparse/drivers/xen/pciback/pciback.h
--- a/linux-2.6-xen-sparse/drivers/xen/pciback/pciback.h	Sat Apr 22 09:41:53 2006
+++ b/linux-2.6-xen-sparse/drivers/xen/pciback/pciback.h	Mon Apr 24 13:34:23 2006
@@ -11,6 +11,8 @@
 #include <xen/xenbus.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
+#include <linux/workqueue.h>
+#include <asm/atomic.h>
 #include <xen/interface/io/pciif.h>
 
 struct pci_dev_entry {
@@ -30,6 +32,12 @@
 	int evtchn_irq;
 
 	struct xen_pci_sharedinfo *sh_info;
+
+	/* op_in_progress == 0 when a request from the frontend is being
+	 * processed. op_in_progress == 1 when it is available. */
+	atomic_t op_in_progress;
+
+	struct work_struct op_work;
 };
 
 struct pciback_dev_data {
@@ -70,6 +78,7 @@
 
 /* Handles events from front-end */
 irqreturn_t pciback_handle_event(int irq, void *dev_id, struct pt_regs *regs);
+void pciback_do_op(void *data);
 
 int pciback_xenbus_register(void);
 void pciback_xenbus_unregister(void);
diff -r 1020c52c58c1 -r ba12bfbe2f5c linux-2.6-xen-sparse/drivers/xen/pciback/pciback_ops.c
--- a/linux-2.6-xen-sparse/drivers/xen/pciback/pciback_ops.c	Sat Apr 22 09:41:53 2006
+++ b/linux-2.6-xen-sparse/drivers/xen/pciback/pciback_ops.c	Mon Apr 24 13:34:23 2006
@@ -40,17 +40,11 @@
 	pciback_config_reset(dev);
 }
 
-irqreturn_t pciback_handle_event(int irq, void *dev_id, struct pt_regs *regs)
+void pciback_do_op(void *data)
 {
-	struct pciback_device *pdev = dev_id;
+	struct pciback_device *pdev = data;
 	struct pci_dev *dev;
 	struct xen_pci_op *op = &pdev->sh_info->op;
-
-	if (unlikely(!test_bit(_XEN_PCIF_active,
-			       (unsigned long *)&pdev->sh_info->flags))) {
-		pr_debug("pciback: interrupt, but no active operation\n");
-		goto out;
-	}
 
 	dev = pciback_get_pci_dev(pdev, op->domain, op->bus, op->devfn);
 
@@ -65,9 +59,31 @@
 	else
 		op->err = XEN_PCI_ERR_not_implemented;
 
+	/* Mark that we're done */
+	atomic_inc(&pdev->op_in_progress);
+
+	/* Tell the driver domain that we're done */
 	wmb();
 	clear_bit(_XEN_PCIF_active, (unsigned long *)&pdev->sh_info->flags);
 	notify_remote_via_irq(pdev->evtchn_irq);
+}
+
+irqreturn_t pciback_handle_event(int irq, void *dev_id, struct pt_regs *regs)
+{
+	struct pciback_device *pdev = dev_id;
+
+	if (unlikely(!test_bit(_XEN_PCIF_active,
+			       (unsigned long *)&pdev->sh_info->flags))) {
+		pr_debug("pciback: interrupt, but no active operation\n");
+		goto out;
+	}
+
+	/* Make sure driver domain doesn't trigger another interrupt while
+	 * we're still processing the last one */
+	if (atomic_dec_and_test(&pdev->op_in_progress))
+		schedule_work(&pdev->op_work);
+	else
+		atomic_inc(&pdev->op_in_progress);
 
       out:
 	return IRQ_HANDLED;
diff -r 1020c52c58c1 -r ba12bfbe2f5c linux-2.6-xen-sparse/drivers/xen/pciback/xenbus.c
--- a/linux-2.6-xen-sparse/drivers/xen/pciback/xenbus.c	Sat Apr 22 09:41:53 2006
+++ b/linux-2.6-xen-sparse/drivers/xen/pciback/xenbus.c	Mon Apr 24 13:34:23 2006
@@ -30,6 +30,9 @@
 	pdev->evtchn_irq = INVALID_EVTCHN_IRQ;
 	pdev->be_watching = 0;
 
+	atomic_set(&pdev->op_in_progress, 1);
+	INIT_WORK(&pdev->op_work, pciback_do_op, pdev);
+
 	if (pciback_init_devices(pdev)) {
 		kfree(pdev);
 		pdev = NULL;
@@ -46,6 +49,11 @@
 	/* Ensure the guest can't trigger our handler before removing devices */
 	if (pdev->evtchn_irq != INVALID_EVTCHN_IRQ)
 		unbind_from_irqhandler(pdev->evtchn_irq, pdev);
+
+	/* If the driver domain started an op, make sure we complete it or
+	 * delete it before releasing the shared memory */
+	cancel_delayed_work(&pdev->op_work);
+	flush_scheduled_work();
 
 	if (pdev->sh_info)
 		xenbus_unmap_ring_vfree(pdev->xdev, pdev->sh_info);