From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <4D901429.5010807@ozlabs.org> Date: Mon, 28 Mar 2011 15:52:57 +1100 From: Matt Evans MIME-Version: 1.0 To: sarah.a.sharp@linux.intel.com Subject: [PATCH v2 3/5] xhci: Add rmb() between reading event validity & event data access. References: <4D8C47CD.3020108@ozlabs.org> <61164.94.211.195.167.1301094709.squirrel@gate.crashing.org> In-Reply-To: <61164.94.211.195.167.1301094709.squirrel@gate.crashing.org> Content-Type: text/plain; charset=ISO-8859-1 Cc: linuxppc-dev@ozlabs.org, linux-usb@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On weakly-ordered systems, the reading of an event's content must occur after reading the event's validity. Signed-off-by: Matt Evans --- Segher, thanks for the comment; explanation added. drivers/usb/host/xhci-ring.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c index 45f3b77..d6aa880 100644 --- a/drivers/usb/host/xhci-ring.c +++ b/drivers/usb/host/xhci-ring.c @@ -2152,6 +2152,11 @@ static void xhci_handle_event(struct xhci_hcd *xhci) } xhci_dbg(xhci, "%s - OS owns TRB\n", __func__); + /* + * Barrier between reading the TRB_CYCLE (valid) flag above and any + * speculative reads of the event's flags/data below. + */ + rmb(); /* FIXME: Handle more event types. */ switch ((le32_to_cpu(event->event_cmd.flags) & TRB_TYPE_BITMASK)) { case TRB_TYPE(TRB_COMPLETION): -- 1.7.0.4