Module Name: src
Committed By: riastradh
Date: Sat May 14 19:44:26 UTC 2022
Modified Files:
src/sys/dev/usb: xhci.c
Log Message:
xhci(4): Fix edge case in simultaneous xfer abort and failure.
On successful usbd_xfer_trycomplete, caller must set ux_status and
call usb_transfer_complete before releasing the pipe (bus) lock.
Failing to call usb_transfer_complete is a mistake. Presumably this
was intended to claim the xfer to complete it only on the last
packet.
I previously introduced the violation of this rule when the code
looked like
xfer->ux_status = err;
if (trb stuff)
usb_transfer_complete(xfer);
I mostly mechanically changed all the assignments of xfer->ux_status
to do usbd_xfer_trycomplete first and then usb_transfer_complete.
In the original, the extra assignment of xfer->ux_status in the event
we _don't_ immediately call usb_transfer_complete was likely
redundant and (except insofar as the abort protocol was broken)
harmless. But now it is a problem because of the contract between
usbd_xfer_trycomplete and usb_transfer_complete under the pipe (bus)
lock. In retrospect, the original probably should have been
if (trb stuff) {
xfer->ux_status = err;
usb_transfer_complete(xfer);
}
and my mechanical transformation should have worked, but also in
retrospect I should have put more thought into the change and done it
a little less mechanically.
To generate a diff of this commit:
cvs rdiff -u -r1.164 -r1.165 src/sys/dev/usb/xhci.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/dev/usb/xhci.c
diff -u src/sys/dev/usb/xhci.c:1.164 src/sys/dev/usb/xhci.c:1.165
--- src/sys/dev/usb/xhci.c:1.164 Wed Apr 6 22:01:45 2022
+++ src/sys/dev/usb/xhci.c Sat May 14 19:44:26 2022
@@ -1,4 +1,4 @@
-/* $NetBSD: xhci.c,v 1.164 2022/04/06 22:01:45 mlelstv Exp $ */
+/* $NetBSD: xhci.c,v 1.165 2022/05/14 19:44:26 riastradh Exp $ */
/*
* Copyright (c) 2013 Jonathan A. Kollasch
@@ -34,7 +34,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xhci.c,v 1.164 2022/04/06 22:01:45 mlelstv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xhci.c,v 1.165 2022/05/14 19:44:26 riastradh Exp $");
#ifdef _KERNEL_OPT
#include "opt_usb.h"
@@ -2473,18 +2473,18 @@ xhci_event_transfer(struct xhci_softc *
break;
}
- /*
- * Try to claim this xfer for completion. If it has already
- * completed or aborted, drop it on the floor.
- */
- if (!usbd_xfer_trycomplete(xfer))
- return;
-
- /* Set the status. */
- xfer->ux_status = err;
-
if ((trb_3 & XHCI_TRB_3_ED_BIT) == 0 ||
(trb_0 & 0x3) == 0x0) {
+ /*
+ * Try to claim this xfer for completion. If it has
+ * already completed or aborted, drop it on the floor.
+ */
+ if (!usbd_xfer_trycomplete(xfer))
+ return;
+
+ /* Set the status. */
+ xfer->ux_status = err;
+
usb_transfer_complete(xfer);
}
}
