USB: introduce usb_anchor

- introduction of usb_anchor and its methods

Signed-off-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

3 files changed, 123 insertions, 3 deletions

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index c5a2f83991dc..87d6edf11f92 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1410,6 +1410,8 @@ void usb_hcd_giveback_urb (struct usb_hcd *hcd, struct urb *urb)
         }
 
         usbmon_urb_complete (&hcd->self, urb);
+        usb_unanchor_urb(urb);
+
         /* pass ownership to the completion handler */
         urb->complete (urb);
         atomic_dec (&urb->use_count);
diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 94ea9727ff55..ac4273dddf34 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -4,6 +4,7 @@
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/usb.h>
+#include <linux/wait.h>
 #include "hcd.h"
 
 #define to_urb(d) container_of(d, struct urb, kref)
@@ -11,6 +12,7 @@
 static void urb_destroy(struct kref *kref)
 {
         struct urb *urb = to_urb(kref);
+
         kfree(urb);
 }
 
@@ -34,6 +36,7 @@ void usb_init_urb(struct urb *urb)
                 memset(urb, 0, sizeof(*urb));
                 kref_init(&urb->kref);
                 spin_lock_init(&urb->lock);
+                INIT_LIST_HEAD(&urb->anchor_list);
         }
 }
 
@@ -100,8 +103,60 @@ struct urb * usb_get_urb(struct urb *urb)
                 kref_get(&urb->kref);
         return urb;
 }
-                
-                
+
+/**
+ * usb_anchor_urb - anchors an URB while it is processed
+ * @urb: pointer to the urb to anchor
+ * @anchor: pointer to the anchor
+ *
+ * This can be called to have access to URBs which are to be executed
+ * without bothering to track them
+ */
+void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&anchor->lock, flags);
+        usb_get_urb(urb);
+        list_add_tail(&urb->anchor_list, &anchor->urb_list);
+        urb->anchor = anchor;
+        spin_unlock_irqrestore(&anchor->lock, flags);
+}
+EXPORT_SYMBOL_GPL(usb_anchor_urb);
+
+/**
+ * usb_unanchor_urb - unanchors an URB
+ * @urb: pointer to the urb to anchor
+ *
+ * Call this to stop the system keeping track of this URB
+ */
+void usb_unanchor_urb(struct urb *urb)
+{
+        unsigned long flags;
+        struct usb_anchor *anchor;
+
+        if (!urb)
+                return;
+
+        anchor = urb->anchor;
+        if (!anchor)
+                return;
+
+        spin_lock_irqsave(&anchor->lock, flags);
+        if (unlikely(anchor != urb->anchor)) {
+                /* we've lost the race to another thread */
+                spin_unlock_irqrestore(&anchor->lock, flags);
+                return;
+        }
+        urb->anchor = NULL;
+        list_del(&urb->anchor_list);
+        spin_unlock_irqrestore(&anchor->lock, flags);
+        usb_put_urb(urb);
+        if (list_empty(&anchor->urb_list))
+                wake_up(&anchor->wait);
+}
+EXPORT_SYMBOL_GPL(usb_unanchor_urb);
+
 /*-------------------------------------------------------------------*/
 
 /**
@@ -478,6 +533,48 @@ void usb_kill_urb(struct urb *urb)
         spin_unlock_irq(&urb->lock);
 }
 
+/**
+ * usb_kill_anchored_urbs - cancel transfer requests en masse
+ * @anchor: anchor the requests are bound to
+ *
+ * this allows all outstanding URBs to be killed starting
+ * from the back of the queue
+ */
+void usb_kill_anchored_urbs(struct usb_anchor *anchor)
+{
+        struct urb *victim;
+
+        spin_lock_irq(&anchor->lock);
+        while (!list_empty(&anchor->urb_list)) {
+                victim = list_entry(anchor->urb_list.prev, struct urb, anchor_list);
+                /* we must make sure the URB isn't freed before we kill it*/
+                usb_get_urb(victim);
+                spin_unlock_irq(&anchor->lock);
+                /* this will unanchor the URB */
+                usb_kill_urb(victim);
+                usb_put_urb(victim);
+                spin_lock_irq(&anchor->lock);
+        }
+        spin_unlock_irq(&anchor->lock);
+}
+EXPORT_SYMBOL_GPL(usb_kill_anchored_urbs);
+
+/**
+ * usb_wait_anchor_empty_timeout - wait for an anchor to be unused
+ * @anchor: the anchor you want to become unused
+ * @timeout: how long you are willing to wait in milliseconds
+ *
+ * Call this is you want to be sure all an anchor's
+ * URBs have finished
+ */
+int usb_wait_anchor_empty_timeout(struct usb_anchor *anchor,
+                                  unsigned int timeout)
+{
+        return wait_event_timeout(anchor->wait, list_empty(&anchor->urb_list),
+                                  msecs_to_jiffies(timeout));
+}
+EXPORT_SYMBOL_GPL(usb_wait_anchor_empty_timeout);
+
 EXPORT_SYMBOL(usb_init_urb);
 EXPORT_SYMBOL(usb_alloc_urb);
 EXPORT_SYMBOL(usb_free_urb);
@@ -485,4 +582,3 @@ EXPORT_SYMBOL(usb_get_urb);
 EXPORT_SYMBOL(usb_submit_urb);
 EXPORT_SYMBOL(usb_unlink_urb);
 EXPORT_SYMBOL(usb_kill_urb);
-
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 98e0338664fb..0873c6219efc 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1000,11 +1000,26 @@ struct usb_iso_packet_descriptor {
 
 struct urb;
 
+struct usb_anchor {
+        struct list_head urb_list;
+        wait_queue_head_t wait;
+        spinlock_t lock;
+};
+
+static inline void init_usb_anchor(struct usb_anchor *anchor)
+{
+        INIT_LIST_HEAD(&anchor->urb_list);
+        init_waitqueue_head(&anchor->wait);
+        spin_lock_init(&anchor->lock);
+}
+
 typedef void (*usb_complete_t)(struct urb *);
 
 /**
  * struct urb - USB Request Block
  * @urb_list: For use by current owner of the URB.
+ * @anchor_list: membership in the list of an anchor
+ * @anchor: to anchor URBs to a common mooring
  * @pipe: Holds endpoint number, direction, type, and more.
  *      Create these values with the eight macros available;
  *      usb_{snd,rcv}TYPEpipe(dev,endpoint), where the TYPE is "ctrl"
@@ -1177,6 +1192,8 @@ struct urb
         /* public: documented fields in the urb that can be used by drivers */
         struct list_head urb_list;      /* list head for use by the urb's
                                          * current owner */
+        struct list_head anchor_list;   /* the URB may be anchored by the driver */
+        struct usb_anchor *anchor;
         struct usb_device *dev;         /* (in) pointer to associated device */
         unsigned int pipe;              /* (in) pipe information */
         int status;                     /* (return) non-ISO status */
@@ -1312,6 +1329,11 @@ extern struct urb *usb_get_urb(struct urb *urb);
 extern int usb_submit_urb(struct urb *urb, gfp_t mem_flags);
 extern int usb_unlink_urb(struct urb *urb);
 extern void usb_kill_urb(struct urb *urb);
+extern void usb_kill_anchored_urbs(struct usb_anchor *anchor);
+extern void usb_anchor_urb(struct urb *urb, struct usb_anchor *anchor);
+extern void usb_unanchor_urb(struct urb *urb);
+extern int usb_wait_anchor_empty_timeout(struct usb_anchor *anchor,
+                                         unsigned int timeout);
 
 void *usb_buffer_alloc (struct usb_device *dev, size_t size,
         gfp_t mem_flags, dma_addr_t *dma);