linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] usb: host: xhci: Handle the right timeout command
@ 2016-12-02 11:21 Baolin Wang
  2016-12-05  2:59 ` Baolin Wang
  0 siblings, 1 reply; 2+ messages in thread
From: Baolin Wang @ 2016-12-02 11:21 UTC (permalink / raw)
  To: mathias.nyman, gregkh; +Cc: linux-usb, linux-kernel, broonie, baolin.wang

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 introduce a counter (xhci->current_cmd_pending) for the number
of pending commands. If we need to cancel the command timer and del_timer()
succeeds, we decrement the number of pending commands. If del_timer() fails,
we leave the number of pending commands alone.

For handling timeout command, in xhci_handle_command_timeout() we will check
the counter after decrementing it, if the counter (xhci->current_cmd_pending)
is 0, which means xhci->current_cmd is the right timeout command. If the
counter (xhci->current_cmd_pending) is greater than 0, which means current
timeout command has been handled by host and host has fetched new command
as xhci->current_cmd, then just return and wait for new current command.

Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
---
This patch is based on Lu Baolu's new fix patch:
usb: xhci: fix possible wild pointer
---
 drivers/usb/host/xhci-ring.c |   26 +++++++++++++++++++++++++-
 drivers/usb/host/xhci.h      |    1 +
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 62dd1c7..a62904e 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1253,6 +1253,7 @@ static void xhci_handle_stopped_cmd_ring(struct xhci_hcd *xhci,
 	if ((xhci->cmd_ring->dequeue != xhci->cmd_ring->enqueue) &&
 	    !(xhci->xhc_state & XHCI_STATE_DYING)) {
 		xhci->current_cmd = cur_cmd;
+		xhci->current_cmd_pending++;
 		mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);
 		xhci_ring_cmd_db(xhci);
 	}
@@ -1274,6 +1275,21 @@ void xhci_handle_command_timeout(unsigned long data)
 		return;
 	}
 
+	xhci->current_cmd_pending--;
+	/*
+	 * If the current_cmd_pending is 0, which means current command is
+	 * timeout.
+	 *
+	 * If the current_cmd_pending is greater than 0, which means current
+	 * timeout command has been handled by host and host has fetched new
+	 * command as xhci->current_cmd, then just return and wait for new
+	 * current command.
+	 */
+	if (xhci->current_cmd_pending > 0) {
+		spin_unlock_irqrestore(&xhci->lock, flags);
+		return;
+	}
+
 	if (xhci->current_cmd->status == COMP_CMD_ABORT)
 		second_timeout = true;
 	xhci->current_cmd->status = COMP_CMD_ABORT;
@@ -1336,7 +1352,13 @@ static void handle_cmd_completion(struct xhci_hcd *xhci,
 
 	cmd = list_entry(xhci->cmd_list.next, struct xhci_command, cmd_list);
 
-	del_timer(&xhci->cmd_timer);
+	/*
+	 * If the command timer is running on another CPU, we don't decrement
+	 * current_cmd_pending, since we didn't successfully stop the command
+	 * timer.
+	 */
+	if (del_timer(&xhci->cmd_timer))
+		xhci->current_cmd_pending--;
 
 	trace_xhci_cmd_completion(cmd_trb, (struct xhci_generic_trb *) event);
 
@@ -1424,6 +1446,7 @@ static void handle_cmd_completion(struct xhci_hcd *xhci,
 	if (cmd->cmd_list.next != &xhci->cmd_list) {
 		xhci->current_cmd = list_entry(cmd->cmd_list.next,
 					       struct xhci_command, cmd_list);
+		xhci->current_cmd_pending++;
 		mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);
 	} else if (xhci->current_cmd == cmd) {
 		xhci->current_cmd = NULL;
@@ -3924,6 +3947,7 @@ static int queue_command(struct xhci_hcd *xhci, struct xhci_command *cmd,
 	if (xhci->cmd_list.next == &cmd->cmd_list &&
 	    !timer_pending(&xhci->cmd_timer)) {
 		xhci->current_cmd = cmd;
+		xhci->current_cmd_pending++;
 		mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);
 	}
 
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 9dbaacf..5d81257 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1567,6 +1567,7 @@ struct xhci_hcd {
 	unsigned int		cmd_ring_reserved_trbs;
 	struct timer_list	cmd_timer;
 	struct xhci_command	*current_cmd;
+	u32			current_cmd_pending;
 	struct xhci_ring	*event_ring;
 	struct xhci_erst	erst;
 	/* Scratchpad */
-- 
1.7.9.5

^ permalink raw reply related	[flat|nested] 2+ messages in thread
* Re: [PATCH] usb: host: xhci: Handle the right timeout command
  2016-12-02 11:21 [PATCH] usb: host: xhci: Handle the right timeout command Baolin Wang
@ 2016-12-05  2:59 ` Baolin Wang
  0 siblings, 0 replies; 2+ messages in thread
From: Baolin Wang @ 2016-12-05  2:59 UTC (permalink / raw)
  To: mathias.nyman, Greg KH; +Cc: USB, LKML, Mark Brown, Baolin Wang

On 2 December 2016 at 19:21, Baolin Wang <baolin.wang@linaro.org> wrote:
> 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 introduce a counter (xhci->current_cmd_pending) for the number
> of pending commands. If we need to cancel the command timer and del_timer()
> succeeds, we decrement the number of pending commands. If del_timer() fails,
> we leave the number of pending commands alone.
>
> For handling timeout command, in xhci_handle_command_timeout() we will check
> the counter after decrementing it, if the counter (xhci->current_cmd_pending)
> is 0, which means xhci->current_cmd is the right timeout command. If the
> counter (xhci->current_cmd_pending) is greater than 0, which means current
> timeout command has been handled by host and host has fetched new command
> as xhci->current_cmd, then just return and wait for new current command.
>
> Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
> ---
> This patch is based on Lu Baolu's new fix patch:
> usb: xhci: fix possible wild pointer
> ---
>  drivers/usb/host/xhci-ring.c |   26 +++++++++++++++++++++++++-
>  drivers/usb/host/xhci.h      |    1 +
>  2 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
> index 62dd1c7..a62904e 100644
> --- a/drivers/usb/host/xhci-ring.c
> +++ b/drivers/usb/host/xhci-ring.c
> @@ -1253,6 +1253,7 @@ static void xhci_handle_stopped_cmd_ring(struct xhci_hcd *xhci,
>         if ((xhci->cmd_ring->dequeue != xhci->cmd_ring->enqueue) &&
>             !(xhci->xhc_state & XHCI_STATE_DYING)) {
>                 xhci->current_cmd = cur_cmd;
> +               xhci->current_cmd_pending++;
>                 mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);
>                 xhci_ring_cmd_db(xhci);
>         }
> @@ -1274,6 +1275,21 @@ void xhci_handle_command_timeout(unsigned long data)
>                 return;
>         }
>
> +       xhci->current_cmd_pending--;

I realized I should move the decrement before 'xhci->current_cmd'
checking, and I will wait for a while for new comments before sending
out v2 patch.

> +       /*
> +        * If the current_cmd_pending is 0, which means current command is
> +        * timeout.
> +        *
> +        * If the current_cmd_pending is greater than 0, which means current
> +        * timeout command has been handled by host and host has fetched new
> +        * command as xhci->current_cmd, then just return and wait for new
> +        * current command.
> +        */
> +       if (xhci->current_cmd_pending > 0) {
> +               spin_unlock_irqrestore(&xhci->lock, flags);
> +               return;
> +       }
> +
>         if (xhci->current_cmd->status == COMP_CMD_ABORT)
>                 second_timeout = true;
>         xhci->current_cmd->status = COMP_CMD_ABORT;
> @@ -1336,7 +1352,13 @@ static void handle_cmd_completion(struct xhci_hcd *xhci,
>
>         cmd = list_entry(xhci->cmd_list.next, struct xhci_command, cmd_list);
>
> -       del_timer(&xhci->cmd_timer);
> +       /*
> +        * If the command timer is running on another CPU, we don't decrement
> +        * current_cmd_pending, since we didn't successfully stop the command
> +        * timer.
> +        */
> +       if (del_timer(&xhci->cmd_timer))
> +               xhci->current_cmd_pending--;
>
>         trace_xhci_cmd_completion(cmd_trb, (struct xhci_generic_trb *) event);
>
> @@ -1424,6 +1446,7 @@ static void handle_cmd_completion(struct xhci_hcd *xhci,
>         if (cmd->cmd_list.next != &xhci->cmd_list) {
>                 xhci->current_cmd = list_entry(cmd->cmd_list.next,
>                                                struct xhci_command, cmd_list);
> +               xhci->current_cmd_pending++;
>                 mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);
>         } else if (xhci->current_cmd == cmd) {
>                 xhci->current_cmd = NULL;
> @@ -3924,6 +3947,7 @@ static int queue_command(struct xhci_hcd *xhci, struct xhci_command *cmd,
>         if (xhci->cmd_list.next == &cmd->cmd_list &&
>             !timer_pending(&xhci->cmd_timer)) {
>                 xhci->current_cmd = cmd;
> +               xhci->current_cmd_pending++;
>                 mod_timer(&xhci->cmd_timer, jiffies + XHCI_CMD_DEFAULT_TIMEOUT);
>         }
>
> diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
> index 9dbaacf..5d81257 100644
> --- a/drivers/usb/host/xhci.h
> +++ b/drivers/usb/host/xhci.h
> @@ -1567,6 +1567,7 @@ struct xhci_hcd {
>         unsigned int            cmd_ring_reserved_trbs;
>         struct timer_list       cmd_timer;
>         struct xhci_command     *current_cmd;
> +       u32                     current_cmd_pending;
>         struct xhci_ring        *event_ring;
>         struct xhci_erst        erst;
>         /* Scratchpad */
> --
> 1.7.9.5
>



-- 
Baolin.wang
Best Regards

^ permalink raw reply	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2016-12-05  3:00 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-12-02 11:21 [PATCH] usb: host: xhci: Handle the right timeout command Baolin Wang
2016-12-05  2:59 ` Baolin Wang

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).