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@@ -32,7 +32,6 @@
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#include <linux/spinlock.h>
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#include <linux/errno.h>
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#include <linux/smp_lock.h>
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-#include <linux/rwsem.h>
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#include <linux/usb.h>
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#include <asm/io.h>
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@@ -49,8 +48,6 @@ const char *usbcore_name = "usbcore";
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static int nousb; /* Disable USB when built into kernel image */
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/* Not honored on modular build */
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-static DECLARE_RWSEM(usb_all_devices_rwsem);
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-
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/**
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* usb_ifnum_to_if - get the interface object with a given interface number
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@@ -446,8 +443,6 @@ usb_alloc_dev(struct usb_device *parent, struct usb_bus *bus, unsigned port1)
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dev->parent = parent;
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INIT_LIST_HEAD(&dev->filelist);
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- init_MUTEX(&dev->serialize);
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-
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return dev;
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}
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@@ -520,75 +515,20 @@ void usb_put_intf(struct usb_interface *intf)
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/* USB device locking
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*
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- * Although locking USB devices should be straightforward, it is
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- * complicated by the way the driver-model core works. When a new USB
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- * driver is registered or unregistered, the core will automatically
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- * probe or disconnect all matching interfaces on all USB devices while
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- * holding the USB subsystem writelock. There's no good way for us to
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- * tell which devices will be used or to lock them beforehand; our only
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- * option is to effectively lock all the USB devices.
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- *
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- * We do that by using a private rw-semaphore, usb_all_devices_rwsem.
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- * When locking an individual device you must first acquire the rwsem's
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- * readlock. When a driver is registered or unregistered the writelock
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- * must be held. These actions are encapsulated in the subroutines
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- * below, so all a driver needs to do is call usb_lock_device() and
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- * usb_unlock_device().
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+ * USB devices and interfaces are locked using the semaphore in their
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+ * embedded struct device. The hub driver guarantees that whenever a
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+ * device is connected or disconnected, drivers are called with the
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+ * USB device locked as well as their particular interface.
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*
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* Complications arise when several devices are to be locked at the same
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* time. Only hub-aware drivers that are part of usbcore ever have to
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- * do this; nobody else needs to worry about it. The problem is that
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- * usb_lock_device() must not be called to lock a second device since it
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- * would acquire the rwsem's readlock reentrantly, leading to deadlock if
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- * another thread was waiting for the writelock. The solution is simple:
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- *
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- * When locking more than one device, call usb_lock_device()
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- * to lock the first one. Lock the others by calling
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- * down(&udev->serialize) directly.
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- *
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- * When unlocking multiple devices, use up(&udev->serialize)
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- * to unlock all but the last one. Unlock the last one by
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- * calling usb_unlock_device().
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+ * do this; nobody else needs to worry about it. The rule for locking
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+ * is simple:
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*
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* When locking both a device and its parent, always lock the
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* the parent first.
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*/
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-/**
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- * usb_lock_device - acquire the lock for a usb device structure
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- * @udev: device that's being locked
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- *
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- * Use this routine when you don't hold any other device locks;
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- * to acquire nested inner locks call down(&udev->serialize) directly.
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- * This is necessary for proper interaction with usb_lock_all_devices().
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- */
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-void usb_lock_device(struct usb_device *udev)
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-{
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- down_read(&usb_all_devices_rwsem);
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- down(&udev->serialize);
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-}
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-
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-/**
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- * usb_trylock_device - attempt to acquire the lock for a usb device structure
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- * @udev: device that's being locked
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- *
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- * Don't use this routine if you already hold a device lock;
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- * use down_trylock(&udev->serialize) instead.
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- * This is necessary for proper interaction with usb_lock_all_devices().
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- *
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- * Returns 1 if successful, 0 if contention.
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- */
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-int usb_trylock_device(struct usb_device *udev)
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-{
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- if (!down_read_trylock(&usb_all_devices_rwsem))
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- return 0;
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- if (down_trylock(&udev->serialize)) {
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- up_read(&usb_all_devices_rwsem);
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- return 0;
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- }
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- return 1;
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-}
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-
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/**
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* usb_lock_device_for_reset - cautiously acquire the lock for a
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* usb device structure
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@@ -627,7 +567,7 @@ int usb_lock_device_for_reset(struct usb_device *udev,
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}
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}
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- while (!usb_trylock_device(udev)) {
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+ while (usb_trylock_device(udev) != 0) {
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/* If we can't acquire the lock after waiting one second,
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* we're probably deadlocked */
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@@ -645,39 +585,6 @@ int usb_lock_device_for_reset(struct usb_device *udev,
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return 1;
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}
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-/**
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- * usb_unlock_device - release the lock for a usb device structure
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- * @udev: device that's being unlocked
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- *
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- * Use this routine when releasing the only device lock you hold;
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- * to release inner nested locks call up(&udev->serialize) directly.
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- * This is necessary for proper interaction with usb_lock_all_devices().
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- */
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-void usb_unlock_device(struct usb_device *udev)
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-{
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- up(&udev->serialize);
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- up_read(&usb_all_devices_rwsem);
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-}
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-
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-/**
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- * usb_lock_all_devices - acquire the lock for all usb device structures
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- *
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- * This is necessary when registering a new driver or probing a bus,
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- * since the driver-model core may try to use any usb_device.
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- */
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-void usb_lock_all_devices(void)
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-{
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- down_write(&usb_all_devices_rwsem);
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-}
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-
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-/**
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- * usb_unlock_all_devices - release the lock for all usb device structures
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- */
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-void usb_unlock_all_devices(void)
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-{
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- up_write(&usb_all_devices_rwsem);
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-}
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-
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static struct usb_device *match_device(struct usb_device *dev,
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u16 vendor_id, u16 product_id)
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@@ -700,10 +607,10 @@ static struct usb_device *match_device(struct usb_device *dev,
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/* look through all of the children of this device */
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for (child = 0; child < dev->maxchild; ++child) {
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if (dev->children[child]) {
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- down(&dev->children[child]->serialize);
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+ usb_lock_device(dev->children[child]);
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ret_dev = match_device(dev->children[child],
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vendor_id, product_id);
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- up(&dev->children[child]->serialize);
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+ usb_unlock_device(dev->children[child]);
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if (ret_dev)
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goto exit;
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}
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@@ -1300,10 +1207,7 @@ EXPORT_SYMBOL(usb_put_dev);
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EXPORT_SYMBOL(usb_get_dev);
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EXPORT_SYMBOL(usb_hub_tt_clear_buffer);
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-EXPORT_SYMBOL(usb_lock_device);
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-EXPORT_SYMBOL(usb_trylock_device);
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EXPORT_SYMBOL(usb_lock_device_for_reset);
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-EXPORT_SYMBOL(usb_unlock_device);
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EXPORT_SYMBOL(usb_driver_claim_interface);
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EXPORT_SYMBOL(usb_driver_release_interface);
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Alan Stern