linux-kernel - [PATCH v2 2/2] usb: host: xhci: Handle the right timeout command

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Message-Id: <99414f74354db54aa4637ef82b0f491762219b98.1482212656.git.baolin.wang@linaro.org>
Date:   Tue, 20 Dec 2016 13:59:51 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     mathias.nyman@...el.com, gregkh@...uxfoundation.org
Cc:     baolu.lu@...ux.intel.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, broonie@...nel.org,
        baolin.wang@...aro.org, linaro-kernel@...ts.linaro.org
Subject: [PATCH v2 2/2] usb: host: xhci: Handle the right timeout command

If a command event is found on the event ring during an interrupt,
we need to stop the command timer with del_timer(). Since del_timer()
can fail if the timer is running and waiting on the xHCI lock, then
it maybe get the wrong timeout command in xhci_handle_command_timeout()
if host fetched a new command and updated the xhci->current_cmd in
handle_cmd_completion(). For this situation, we need a way to signal
to the command timer that everything is fine and it should exit.

We should check if the command timer is pending in xhci_handle_command_timeout()
function, if the command timer is pending, which means current timeout
command has been handled by host and host has fetched new command and
re-added the command timer, then just return and wait for new current
command. If not, it means current command is timeout and need to be
handled.

Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
---
Changes since v1:
 - Remove the counter and just check if the command timer is pending.
---
 drivers/usb/host/xhci-ring.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9965a4c..3947344 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1269,7 +1269,7 @@ void xhci_handle_command_timeout(unsigned long data)
 	xhci = (struct xhci_hcd *) data;

 	spin_lock_irqsave(&xhci->lock, flags);
-	if (!xhci->current_cmd) {
+	if (!xhci->current_cmd || timer_pending(&xhci->cmd_timer)) {
 		spin_unlock_irqrestore(&xhci->lock, flags);
 		return;
 	}
-- 
1.7.9.5