USB: xhci: Respect critical sections.

Narrow down time spent holding the xHCI spinlock so that it's only used to
protect the xHCI rings, not as mutual exclusion.  Stop allocating memory
while holding the spinlock and calling xhci_alloc_virt_device() and
xhci_endpoint_init().

The USB core should have locking in it to prevent device state to be
manipulated by more than one kernel thread.  E.g. you can't free a device
while you're in the middle of setting a new configuration.  So removing
the locks from the sections where xhci_alloc_dev() and
xhci_reset_bandwidth() touch xHCI's representation of the device should be
OK.

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 37 insertions, 35 deletions

diff --git a/drivers/usb/host/xhci-hcd.c b/drivers/usb/host/xhci-hcd.c
index 489657c853e..dba3e07ccd0 100644
--- a/drivers/usb/host/xhci-hcd.c
+++ b/drivers/usb/host/xhci-hcd.c
@@ -687,11 +687,14 @@ done:
  * different endpoint descriptor in usb_host_endpoint.
  * A call to xhci_add_endpoint() followed by a call to xhci_drop_endpoint() is
  * not allowed.
+ *
+ * The USB core will not allow URBs to be queued to an endpoint that is being
+ * disabled, so there's no need for mutual exclusion to protect
+ * the xhci->devs[slot_id] structure.
  */
 int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
                 struct usb_host_endpoint *ep)
 {
-        unsigned long flags;
         struct xhci_hcd *xhci;
         struct xhci_device_control *in_ctx;
         unsigned int last_ctx;
@@ -714,11 +717,9 @@ int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
                 return 0;
         }
 
-        spin_lock_irqsave(&xhci->lock, flags);
         if (!xhci->devs || !xhci->devs[udev->slot_id]) {
                 xhci_warn(xhci, "xHCI %s called with unaddressed device\n",
                                 __func__);
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return -EINVAL;
         }
 
@@ -732,7 +733,6 @@ int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
                         in_ctx->drop_flags & xhci_get_endpoint_flag(&ep->desc)) {
                 xhci_warn(xhci, "xHCI %s called with disabled ep %p\n",
                                 __func__, ep);
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return 0;
         }
 
@@ -752,8 +752,6 @@ int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
 
         xhci_endpoint_zero(xhci, xhci->devs[udev->slot_id], ep);
 
-        spin_unlock_irqrestore(&xhci->lock, flags);
-
         xhci_dbg(xhci, "drop ep 0x%x, slot id %d, new drop flags = %#x, new add flags = %#x, new slot info = %#x\n",
                         (unsigned int) ep->desc.bEndpointAddress,
                         udev->slot_id,
@@ -771,11 +769,14 @@ int xhci_drop_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
  * different endpoint descriptor in usb_host_endpoint.
  * A call to xhci_add_endpoint() followed by a call to xhci_drop_endpoint() is
  * not allowed.
+ *
+ * The USB core will not allow URBs to be queued to an endpoint until the
+ * configuration or alt setting is installed in the device, so there's no need
+ * for mutual exclusion to protect the xhci->devs[slot_id] structure.
  */
 int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
                 struct usb_host_endpoint *ep)
 {
-        unsigned long flags;
         struct xhci_hcd *xhci;
         struct xhci_device_control *in_ctx;
         unsigned int ep_index;
@@ -802,11 +803,9 @@ int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
                 return 0;
         }
 
-        spin_lock_irqsave(&xhci->lock, flags);
         if (!xhci->devs || !xhci->devs[udev->slot_id]) {
                 xhci_warn(xhci, "xHCI %s called with unaddressed device\n",
                                 __func__);
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return -EINVAL;
         }
 
@@ -819,14 +818,18 @@ int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
         if (in_ctx->add_flags & xhci_get_endpoint_flag(&ep->desc)) {
                 xhci_warn(xhci, "xHCI %s called with enabled ep %p\n",
                                 __func__, ep);
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return 0;
         }
 
-        if (xhci_endpoint_init(xhci, xhci->devs[udev->slot_id], udev, ep) < 0) {
+        /*
+         * Configuration and alternate setting changes must be done in
+         * process context, not interrupt context (or so documenation
+         * for usb_set_interface() and usb_set_configuration() claim).
+         */
+        if (xhci_endpoint_init(xhci, xhci->devs[udev->slot_id],
+                                udev, ep, GFP_KERNEL) < 0) {
                 dev_dbg(&udev->dev, "%s - could not initialize ep %#x\n",
                                 __func__, ep->desc.bEndpointAddress);
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return -ENOMEM;
         }
 
@@ -847,7 +850,6 @@ int xhci_add_endpoint(struct usb_hcd *hcd, struct usb_device *udev,
                 in_ctx->slot.dev_info |= LAST_CTX(last_ctx);
         }
         new_slot_info = in_ctx->slot.dev_info;
-        spin_unlock_irqrestore(&xhci->lock, flags);
 
         xhci_dbg(xhci, "add ep 0x%x, slot id %d, new drop flags = %#x, new add flags = %#x, new slot info = %#x\n",
                         (unsigned int) ep->desc.bEndpointAddress,
@@ -883,6 +885,16 @@ static void xhci_zero_in_ctx(struct xhci_virt_device *virt_dev)
         }
 }
 
+/* Called after one or more calls to xhci_add_endpoint() or
+ * xhci_drop_endpoint().  If this call fails, the USB core is expected
+ * to call xhci_reset_bandwidth().
+ *
+ * Since we are in the middle of changing either configuration or
+ * installing a new alt setting, the USB core won't allow URBs to be
+ * enqueued for any endpoint on the old config or interface.  Nothing
+ * else should be touching the xhci->devs[slot_id] structure, so we
+ * don't need to take the xhci->lock for manipulating that.
+ */
 int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
 {
         int i;
@@ -897,11 +909,9 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
                 return ret;
         xhci = hcd_to_xhci(hcd);
 
-        spin_lock_irqsave(&xhci->lock, flags);
         if (!udev->slot_id || !xhci->devs || !xhci->devs[udev->slot_id]) {
                 xhci_warn(xhci, "xHCI %s called with unaddressed device\n",
                                 __func__);
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return -EINVAL;
         }
         xhci_dbg(xhci, "%s called for udev %p\n", __func__, udev);
@@ -916,11 +926,12 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
         xhci_dbg_ctx(xhci, virt_dev->in_ctx, virt_dev->in_ctx_dma,
                         LAST_CTX_TO_EP_NUM(virt_dev->in_ctx->slot.dev_info));
 
+        spin_lock_irqsave(&xhci->lock, flags);
         ret = xhci_queue_configure_endpoint(xhci, virt_dev->in_ctx_dma,
                         udev->slot_id);
         if (ret < 0) {
-                xhci_dbg(xhci, "FIXME allocate a new ring segment\n");
                 spin_unlock_irqrestore(&xhci->lock, flags);
+                xhci_dbg(xhci, "FIXME allocate a new ring segment\n");
                 return -ENOMEM;
         }
         xhci_ring_cmd_db(xhci);
@@ -937,7 +948,6 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
                 return -ETIME;
         }
 
-        spin_lock_irqsave(&xhci->lock, flags);
         switch (virt_dev->cmd_status) {
         case COMP_ENOMEM:
                 dev_warn(&udev->dev, "Not enough host controller resources "
@@ -968,7 +978,6 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
         }
         if (ret) {
                 /* Callee should call reset_bandwidth() */
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return ret;
         }
 
@@ -986,14 +995,11 @@ int xhci_check_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
                 }
         }
 
-        spin_unlock_irqrestore(&xhci->lock, flags);
-
         return ret;
 }
 
 void xhci_reset_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
 {
-        unsigned long flags;
         struct xhci_hcd *xhci;
         struct xhci_virt_device *virt_dev;
         int i, ret;
@@ -1003,11 +1009,9 @@ void xhci_reset_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
                 return;
         xhci = hcd_to_xhci(hcd);
 
-        spin_lock_irqsave(&xhci->lock, flags);
         if (!xhci->devs || !xhci->devs[udev->slot_id]) {
                 xhci_warn(xhci, "xHCI %s called with unaddressed device\n",
                                 __func__);
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return;
         }
         xhci_dbg(xhci, "%s called for udev %p\n", __func__, udev);
@@ -1020,7 +1024,6 @@ void xhci_reset_bandwidth(struct usb_hcd *hcd, struct usb_device *udev)
                 }
         }
         xhci_zero_in_ctx(virt_dev);
-        spin_unlock_irqrestore(&xhci->lock, flags);
 }
 
 /*
@@ -1046,7 +1049,7 @@ void xhci_free_dev(struct usb_hcd *hcd, struct usb_device *udev)
         spin_unlock_irqrestore(&xhci->lock, flags);
         /*
          * Event command completion handler will free any data structures
-         * associated with the slot
+         * associated with the slot.  XXX Can free sleep?
          */
 }
 
@@ -1081,15 +1084,15 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
                 return 0;
         }
 
-        spin_lock_irqsave(&xhci->lock, flags);
         if (!xhci->slot_id) {
                 xhci_err(xhci, "Error while assigning device slot ID\n");
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return 0;
         }
+        /* xhci_alloc_virt_device() does not touch rings; no need to lock */
         if (!xhci_alloc_virt_device(xhci, xhci->slot_id, udev, GFP_KERNEL)) {
                 /* Disable slot, if we can do it without mem alloc */
                 xhci_warn(xhci, "Could not allocate xHCI USB device data structures\n");
+                spin_lock_irqsave(&xhci->lock, flags);
                 if (!xhci_queue_slot_control(xhci, TRB_DISABLE_SLOT, udev->slot_id))
                         xhci_ring_cmd_db(xhci);
                 spin_unlock_irqrestore(&xhci->lock, flags);
@@ -1098,7 +1101,6 @@ int xhci_alloc_dev(struct usb_hcd *hcd, struct usb_device *udev)
         udev->slot_id = xhci->slot_id;
         /* Is this a LS or FS device under a HS hub? */
         /* Hub or peripherial? */
-        spin_unlock_irqrestore(&xhci->lock, flags);
         return 1;
 }
 
@@ -1125,7 +1127,6 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
                 return -EINVAL;
         }
 
-        spin_lock_irqsave(&xhci->lock, flags);
         virt_dev = xhci->devs[udev->slot_id];
 
         /* If this is a Set Address to an unconfigured device, setup ep 0 */
@@ -1133,6 +1134,7 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
                 xhci_setup_addressable_virt_dev(xhci, udev);
         /* Otherwise, assume the core has the device configured how it wants */
 
+        spin_lock_irqsave(&xhci->lock, flags);
         ret = xhci_queue_address_device(xhci, virt_dev->in_ctx_dma,
                         udev->slot_id);
         if (ret) {
@@ -1157,7 +1159,6 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
                 return -ETIME;
         }
 
-        spin_lock_irqsave(&xhci->lock, flags);
         switch (virt_dev->cmd_status) {
         case COMP_CTX_STATE:
         case COMP_EBADSLT:
@@ -1179,7 +1180,6 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
                 break;
         }
         if (ret) {
-                spin_unlock_irqrestore(&xhci->lock, flags);
                 return ret;
         }
         temp = xhci_readl(xhci, &xhci->op_regs->dcbaa_ptr[0]);
@@ -1211,7 +1211,6 @@ int xhci_address_device(struct usb_hcd *hcd, struct usb_device *udev)
         /* Mirror flags in the output context for future ep enable/disable */
         virt_dev->out_ctx->add_flags = SLOT_FLAG | EP0_FLAG;
         virt_dev->out_ctx->drop_flags = 0;
-        spin_unlock_irqrestore(&xhci->lock, flags);
 
         xhci_dbg(xhci, "Device address = %d\n", udev->devnum);
         /* XXX Meh, not sure if anyone else but choose_address uses this. */
diff --git a/drivers/usb/host/xhci-mem.c b/drivers/usb/host/xhci-mem.c
index 37a83878a06..c8a72de1c50 100644
--- a/drivers/usb/host/xhci-mem.c
+++ b/drivers/usb/host/xhci-mem.c
@@ -460,7 +460,8 @@ static inline u32 xhci_get_endpoint_type(struct usb_device *udev,
 int xhci_endpoint_init(struct xhci_hcd *xhci,
                 struct xhci_virt_device *virt_dev,
                 struct usb_device *udev,
-                struct usb_host_endpoint *ep)
+                struct usb_host_endpoint *ep,
+                gfp_t mem_flags)
 {
         unsigned int ep_index;
         struct xhci_ep_ctx *ep_ctx;
@@ -472,7 +473,7 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
         ep_ctx = &virt_dev->in_ctx->ep[ep_index];
 
         /* Set up the endpoint ring */
-        virt_dev->new_ep_rings[ep_index] = xhci_ring_alloc(xhci, 1, true, GFP_KERNEL);
+        virt_dev->new_ep_rings[ep_index] = xhci_ring_alloc(xhci, 1, true, mem_flags);
         if (!virt_dev->new_ep_rings[ep_index])
                 return -ENOMEM;
         ep_ring = virt_dev->new_ep_rings[ep_index];
diff --git a/drivers/usb/host/xhci.h b/drivers/usb/host/xhci.h
index 3e8e09c4c2b..8936eeb5588 100644
--- a/drivers/usb/host/xhci.h
+++ b/drivers/usb/host/xhci.h
@@ -1101,7 +1101,9 @@ int xhci_setup_addressable_virt_dev(struct xhci_hcd *xhci, struct usb_device *ud
 unsigned int xhci_get_endpoint_index(struct usb_endpoint_descriptor *desc);
 unsigned int xhci_get_endpoint_flag(struct usb_endpoint_descriptor *desc);
 void xhci_endpoint_zero(struct xhci_hcd *xhci, struct xhci_virt_device *virt_dev, struct usb_host_endpoint *ep);
-int xhci_endpoint_init(struct xhci_hcd *xhci, struct xhci_virt_device *virt_dev, struct usb_device *udev, struct usb_host_endpoint *ep);
+int xhci_endpoint_init(struct xhci_hcd *xhci, struct xhci_virt_device *virt_dev,
+                struct usb_device *udev, struct usb_host_endpoint *ep,
+                gfp_t mem_flags);
 void xhci_ring_free(struct xhci_hcd *xhci, struct xhci_ring *ring);
 
 #ifdef CONFIG_PCI