svn commit: r188982 - head/sys/dev/usb

[Andrew Thompson]

Author: thompsa
Date: Tue Feb 24 03:38:24 2009
New Revision: 188982
URL: http://svn.freebsd.org/changeset/base/188982

Log:
  MFp4 //depot/projects/usb at 157847
  
  Improvements to "usb2_transfer_setup()" and "usb2_transfer_unsetup()". Set
  "ppxfer[n]" when the transfer setup is complete to prevent races.  Remove
  redundant NULL-checks from "usb2_transfer_unsetup()".
  
  Submitted by:	Hans Petter Selasky

Modified:
  head/sys/dev/usb/usb_transfer.c

Modified: head/sys/dev/usb/usb_transfer.c
==============================================================================
--- head/sys/dev/usb/usb_transfer.c	Tue Feb 24 03:34:05 2009	(r188981)
+++ head/sys/dev/usb/usb_transfer.c	Tue Feb 24 03:38:24 2009	(r188982)
@@ -887,18 +887,14 @@ usb2_transfer_setup(struct usb2_device *
 			parm.size[0] += ((-parm.size[0]) & (USB_HOST_ALIGN - 1));
 
 			if (buf) {
-
 				/*
 				 * Common initialization of the
 				 * "usb2_xfer" structure.
 				 */
 				xfer = USB_ADD_BYTES(buf, parm.size[0]);
-
-				ppxfer[n] = xfer;
 				xfer->address = udev->address;
 				xfer->priv_sc = priv_sc;
 				xfer->xroot = info;
-				info->setup_refcount++;
 
 				usb2_callout_init_mtx(&xfer->timeout_handle,
 				    &udev->bus->bus_mtx, 0);
@@ -915,9 +911,22 @@ usb2_transfer_setup(struct usb2_device *
 				refcount++;
 			}
 
+			/* set transfer pipe pointer */
+			xfer->pipe = pipe;
+
 			parm.size[0] += sizeof(xfer[0]);
+			parm.methods = xfer->pipe->methods;
+			parm.curr_xfer = xfer;
 
-			xfer->pipe = pipe;
+			/*
+			 * Call the Host or Device controller transfer
+			 * setup routine:
+			 */
+			(udev->bus->methods->xfer_setup) (&parm);
+
+			/* check for error */
+			if (parm.err)
+				goto done;
 
 			if (buf) {
 				/*
@@ -930,18 +939,19 @@ usb2_transfer_setup(struct usb2_device *
 				 * want more information.
 				 */
 				xfer->pipe->refcount++;
-			}
-			parm.methods = xfer->pipe->methods;
-			parm.curr_xfer = xfer;
 
-			/*
-			 * Call the Host or Device controller transfer setup
-			 * routine:
-			 */
-			(udev->bus->methods->xfer_setup) (&parm);
+				/*
+				 * Whenever we set ppxfer[] then we
+				 * also need to increment the
+				 * "setup_refcount":
+				 */
+				info->setup_refcount++;
 
-			if (parm.err) {
-				goto done;
+				/*
+				 * Transfer is successfully setup and
+				 * can be used:
+				 */
+				ppxfer[n] = xfer;
 			}
 		}
 
@@ -1121,72 +1131,60 @@ usb2_transfer_unsetup(struct usb2_xfer *
 	while (n_setup--) {
 		xfer = pxfer[n_setup];
 
-		if (xfer) {
-			if (xfer->pipe) {
-				USB_XFER_LOCK(xfer);
-				USB_BUS_LOCK(xfer->xroot->bus);
+		if (xfer == NULL)
+			continue;
 
-				/*
-				 * HINT: when you start/stop a transfer, it
-				 * might be a good idea to directly use the
-				 * "pxfer[]" structure:
-				 *
-				 * usb2_transfer_start(sc->pxfer[0]);
-				 * usb2_transfer_stop(sc->pxfer[0]);
-				 *
-				 * That way, if your code has many parts that
-				 * will not stop running under the same
-				 * lock, in other words "xfer_mtx", the
-				 * usb2_transfer_start and
-				 * usb2_transfer_stop functions will simply
-				 * return when they detect a NULL pointer
-				 * argument.
-				 *
-				 * To avoid any races we clear the "pxfer[]"
-				 * pointer while holding the private mutex
-				 * of the driver:
-				 */
-				pxfer[n_setup] = NULL;
+		info = xfer->xroot;
 
-				USB_BUS_UNLOCK(xfer->xroot->bus);
-				USB_XFER_UNLOCK(xfer);
+		USB_XFER_LOCK(xfer);
+		USB_BUS_LOCK(info->bus);
 
-				usb2_transfer_drain(xfer);
+		/*
+		 * HINT: when you start/stop a transfer, it might be a
+		 * good idea to directly use the "pxfer[]" structure:
+		 *
+		 * usb2_transfer_start(sc->pxfer[0]);
+		 * usb2_transfer_stop(sc->pxfer[0]);
+		 *
+		 * That way, if your code has many parts that will not
+		 * stop running under the same lock, in other words
+		 * "xfer_mtx", the usb2_transfer_start and
+		 * usb2_transfer_stop functions will simply return
+		 * when they detect a NULL pointer argument.
+		 *
+		 * To avoid any races we clear the "pxfer[]" pointer
+		 * while holding the private mutex of the driver:
+		 */
+		pxfer[n_setup] = NULL;
 
-				if (xfer->flags_int.bdma_enable) {
-					needs_delay = 1;
-				}
-				/*
-				 * NOTE: default pipe does not have an
-				 * interface, even if pipe->iface_index == 0
-				 */
-				xfer->pipe->refcount--;
+		USB_BUS_UNLOCK(info->bus);
+		USB_XFER_UNLOCK(xfer);
 
-			} else {
-				/* clear the transfer pointer */
-				pxfer[n_setup] = NULL;
-			}
+		usb2_transfer_drain(xfer);
 
-			usb2_callout_drain(&xfer->timeout_handle);
+		if (xfer->flags_int.bdma_enable)
+			needs_delay = 1;
 
-			if (xfer->xroot) {
-				info = xfer->xroot;
+		/*
+		 * NOTE: default pipe does not have an
+		 * interface, even if pipe->iface_index == 0
+		 */
+		xfer->pipe->refcount--;
 
-				USB_BUS_LOCK(info->bus);
+		usb2_callout_drain(&xfer->timeout_handle);
 
-				USB_ASSERT(info->setup_refcount != 0,
-				    ("Invalid setup "
-				    "reference count!\n"));
+		USB_BUS_LOCK(info->bus);
 
-				info->setup_refcount--;
+		USB_ASSERT(info->setup_refcount != 0, ("Invalid setup "
+		    "reference count!\n"));
 
-				if (info->setup_refcount == 0) {
-					usb2_transfer_unsetup_sub(info,
-					    needs_delay);
-				} else {
-					USB_BUS_UNLOCK(info->bus);
-				}
-			}
+		info->setup_refcount--;
+
+		if (info->setup_refcount == 0) {
+			usb2_transfer_unsetup_sub(info,
+			    needs_delay);
+		} else {
+			USB_BUS_UNLOCK(info->bus);
 		}
 	}
 }