linux-kernel - Re: [PATCH 07/10] xhci: Use command structures when queuing commands on the command ring

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Date:	Thu, 5 Jun 2014 15:16:35 -0700
From:	Dan Williams <dan.j.williams@...il.com>
To:	Mathias Nyman <mathias.nyman@...ux.intel.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	USB list <linux-usb@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>
Subject: Re: [PATCH 07/10] xhci: Use command structures when queuing commands
 on the command ring

Hi Mathias, hit a small issue playing with -next:

On Thu, May 8, 2014 at 9:26 AM, Mathias Nyman
<mathias.nyman@...ux.intel.com> wrote:
> To create a global command queue we require that each command put on the
> command ring is submitted with a command structure.
>
> Functions that queue commands and wait for completion need to allocate a command
> before submitting it, and free it once completed. The following command queuing
> functions need to be modified.
>
> xhci_configure_endpoint()
> xhci_address_device()
> xhci_queue_slot_control()
> xhci_queue_stop_endpoint()
> xhci_queue_new_dequeue_state()
> xhci_queue_reset_ep()
> xhci_configure_endpoint()
>
> xhci_configure_endpoint() could already be called with a command structure,
> and only xhci_check_maxpacket and xhci_check_bandwidth did not do so. These
> are changed and a command structure is now required. This change also simplifies
> the configure endpoint command completion handling and the "goto bandwidth_change"
> handling code can be removed.
>
> In some cases the command queuing function is called in interrupt context.
> These commands needs to be allocated atomically, and they can't wait for
> completion. These commands will in this patch be freed directly after queuing,
> but freeing will be moved to the command completion event handler in a later
> patch once we get the global command queue up.(Just so that we won't leak
> memory in the middle of the patch set)
>
> Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
> ---
>  drivers/usb/host/xhci-hub.c  |  21 +++--
>  drivers/usb/host/xhci-ring.c | 107 +++++++++++++-----------
>  drivers/usb/host/xhci.c      | 194 ++++++++++++++++++++++++++++---------------
>  drivers/usb/host/xhci.h      |  31 +++----
>  4 files changed, 216 insertions(+), 137 deletions(-)
>
> diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
> index 1ad6bc1..3ce9c0a 100644
> --- a/drivers/usb/host/xhci-hub.c
> +++ b/drivers/usb/host/xhci-hub.c
> @@ -20,7 +20,8 @@
>   * Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
>   */
>
> -#include <linux/gfp.h>
> +
> +#include <linux/slab.h>
>  #include <asm/unaligned.h>
>
>  #include "xhci.h"
> @@ -284,12 +285,22 @@ static int xhci_stop_device(struct xhci_hcd *xhci, int slot_id, int suspend)
>
>         spin_lock_irqsave(&xhci->lock, flags);
>         for (i = LAST_EP_INDEX; i > 0; i--) {
> -               if (virt_dev->eps[i].ring && virt_dev->eps[i].ring->dequeue)
> -                       xhci_queue_stop_endpoint(xhci, slot_id, i, suspend);
> +               if (virt_dev->eps[i].ring && virt_dev->eps[i].ring->dequeue) {
> +                       struct xhci_command *command;
> +                       command = xhci_alloc_command(xhci, false, false,
> +                                                    GFP_NOIO);

...this needs to be GFP_NOWAIT, or move it outside the lock.
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