# We may submit more requests to the host than it is prepared to
# handle.  In this case, io_submit returns -EAGAIN.  When this
# happens, we return from submit_aio and sleep on the eagain_queue
# wait_queue.  We are woken from the interrupt handler - if some
# requests have come back from the host, presumably there's some room
# on the host to submit more requests.
#
# Interactions between this wait_queue and the sequence_queue and the
# allocation semaphore - the sequence queue and any allocations always
# happen first.  While looping on this wait_queue, we do nothing but
# try to resubmit to the host.
Index: test/arch/um/drivers/ubd_kern.c
===================================================================
--- test.orig/arch/um/drivers/ubd_kern.c	2005-09-17 17:40:53.000000000 -0400
+++ test/arch/um/drivers/ubd_kern.c	2005-09-17 17:41:03.000000000 -0400
@@ -574,6 +574,9 @@
 
 static int ubd_reply_fd = -1;
 
+DECLARE_WAIT_QUEUE_HEAD(eagain_queue);
+static int dequeued;
+
 static irqreturn_t ubd_intr(int irq, void *dev, struct pt_regs *unused)
 {
 	struct aio_thread_reply reply;
@@ -629,6 +632,9 @@
 	}
 	reactivate_fd(fd, UBD_IRQ);
 
+	dequeued = 1;
+	wake_up(&eagain_queue);
+
 	return(IRQ_HANDLED);
 }
 
@@ -1376,7 +1382,19 @@
                 if(aio->bitmap != NULL)
                         atomic_inc(&aio->bitmap->count);
 
-                err = submit_aio(&aio->aio);
+		while(1){
+			unsigned long flags;
+
+			err = submit_aio(&aio->aio);
+			if(err != -EAGAIN)
+				break;
+			dequeued = 0;
+			local_save_flags(flags);
+			local_irq_enable();
+			wait_event(eagain_queue, dequeued);
+			local_irq_restore(flags);
+		}
+
                 if(err){
                         printk("do_io - submit_aio failed, "
                                "err = %d\n", err);
Index: test/arch/um/os-Linux/aio.c
===================================================================
--- test.orig/arch/um/os-Linux/aio.c	2005-09-17 17:39:33.000000000 -0400
+++ test/arch/um/os-Linux/aio.c	2005-09-17 17:41:03.000000000 -0400
@@ -296,6 +296,9 @@
 	int err;
 
 	err = do_aio(ctx, aio);
+	if(err == -EAGAIN)
+		return err;
+
 	if(err){
 		reply = ((struct aio_thread_reply) { .data = aio,
 					             .err  = err });