Commit 9ad3d6cc authored by Alan Stern's avatar Alan Stern Committed by Greg Kroah-Hartman
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[PATCH] USB: Remove USB private semaphore



This patch (as605) removes the private udev->serialize semaphore,
relying instead on the locking provided by the embedded struct device's
semaphore.  The changes are confined to the core, except that the
usb_trylock_device routine now uses the return convention of
down_trylock rather than down_read_trylock (they return opposite values
for no good reason).

A couple of other associated changes are included as well:

	Now that we aren't concerned about HCDs that avoid using the
	hcd glue layer, usb_disconnect no longer needs to acquire the
	usb_bus_lock -- that can be done by usb_remove_hcd where it
	belongs.

	Devices aren't locked over the same scope of code in
	usb_new_device and hub_port_connect_change as they used to be.
	This shouldn't cause any trouble.

Along with the preceding driver core patch, this needs a lot of testing.
Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
parent 75318d2d
......@@ -545,10 +545,10 @@ static ssize_t usb_device_dump(char __user **buffer, size_t *nbytes, loff_t *ski
struct usb_device *childdev = usbdev->children[chix];
if (childdev) {
down(&childdev->serialize);
usb_lock_device(childdev);
ret = usb_device_dump(buffer, nbytes, skip_bytes, file_offset, childdev,
bus, level + 1, chix, ++cnt);
up(&childdev->serialize);
usb_unlock_device(childdev);
if (ret == -EFAULT)
return total_written;
total_written += ret;
......
......@@ -1349,9 +1349,7 @@ static int proc_ioctl(struct dev_state *ps, struct usbdevfs_ioctl *ctl)
/* let kernel drivers try to (re)bind to the interface */
case USBDEVFS_CONNECT:
usb_unlock_device(ps->dev);
usb_lock_all_devices();
bus_rescan_devices(intf->dev.bus);
usb_unlock_all_devices();
usb_lock_device(ps->dev);
break;
......
......@@ -432,9 +432,7 @@ int usb_register_driver(struct usb_driver *new_driver, struct module *owner)
spin_lock_init(&new_driver->dynids.lock);
INIT_LIST_HEAD(&new_driver->dynids.list);
usb_lock_all_devices();
retval = driver_register(&new_driver->driver);
usb_unlock_all_devices();
if (!retval) {
pr_info("%s: registered new driver %s\n",
......@@ -465,11 +463,9 @@ void usb_deregister(struct usb_driver *driver)
{
pr_info("%s: deregistering driver %s\n", usbcore_name, driver->name);
usb_lock_all_devices();
usb_remove_newid_file(driver);
usb_free_dynids(driver);
driver_unregister(&driver->driver);
usb_unlock_all_devices();
usbfs_update_special();
}
......
......@@ -857,9 +857,7 @@ static int register_root_hub (struct usb_device *usb_dev,
return (retval < 0) ? retval : -EMSGSIZE;
}
usb_lock_device (usb_dev);
retval = usb_new_device (usb_dev);
usb_unlock_device (usb_dev);
if (retval) {
usb_dev->bus->root_hub = NULL;
dev_err (parent_dev, "can't register root hub for %s, %d\n",
......@@ -1891,7 +1889,10 @@ void usb_remove_hcd(struct usb_hcd *hcd)
spin_lock_irq (&hcd_root_hub_lock);
hcd->rh_registered = 0;
spin_unlock_irq (&hcd_root_hub_lock);
down(&usb_bus_list_lock);
usb_disconnect(&hcd->self.root_hub);
up(&usb_bus_list_lock);
hcd->poll_rh = 0;
del_timer_sync(&hcd->rh_timer);
......
......@@ -32,7 +32,7 @@
#include "hub.h"
/* Protect struct usb_device->state and ->children members
* Note: Both are also protected by ->serialize, except that ->state can
* Note: Both are also protected by ->dev.sem, except that ->state can
* change to USB_STATE_NOTATTACHED even when the semaphore isn't held. */
static DEFINE_SPINLOCK(device_state_lock);
......@@ -975,8 +975,8 @@ static int locktree(struct usb_device *udev)
/* when everyone grabs locks top->bottom,
* non-overlapping work may be concurrent
*/
down(&udev->serialize);
up(&hdev->serialize);
usb_lock_device(udev);
usb_unlock_device(hdev);
return t + 1;
}
}
......@@ -1132,16 +1132,10 @@ void usb_disconnect(struct usb_device **pdev)
* this quiesces everyting except pending urbs.
*/
usb_set_device_state(udev, USB_STATE_NOTATTACHED);
/* lock the bus list on behalf of HCDs unregistering their root hubs */
if (!udev->parent) {
down(&usb_bus_list_lock);
usb_lock_device(udev);
} else
down(&udev->serialize);
dev_info (&udev->dev, "USB disconnect, address %d\n", udev->devnum);
usb_lock_device(udev);
/* Free up all the children before we remove this device */
for (i = 0; i < USB_MAXCHILDREN; i++) {
if (udev->children[i])
......@@ -1169,11 +1163,7 @@ void usb_disconnect(struct usb_device **pdev)
*pdev = NULL;
spin_unlock_irq(&device_state_lock);
if (!udev->parent) {
usb_unlock_device(udev);
up(&usb_bus_list_lock);
} else
up(&udev->serialize);
usb_unlock_device(udev);
device_unregister(&udev->dev);
}
......@@ -1243,8 +1233,8 @@ static inline void show_string(struct usb_device *udev, char *id, char *string)
*
* This is called with devices which have been enumerated, but not yet
* configured. The device descriptor is available, but not descriptors
* for any device configuration. The caller must have locked udev and
* either the parent hub (if udev is a normal device) or else the
* for any device configuration. The caller must have locked either
* the parent hub (if udev is a normal device) or else the
* usb_bus_list_lock (if udev is a root hub). The parent's pointer to
* udev has already been installed, but udev is not yet visible through
* sysfs or other filesystem code.
......@@ -1254,8 +1244,7 @@ static inline void show_string(struct usb_device *udev, char *id, char *string)
*
* This call is synchronous, and may not be used in an interrupt context.
*
* Only the hub driver should ever call this; root hub registration
* uses it indirectly.
* Only the hub driver or root-hub registrar should ever call this.
*/
int usb_new_device(struct usb_device *udev)
{
......@@ -1364,6 +1353,8 @@ int usb_new_device(struct usb_device *udev)
}
usb_create_sysfs_dev_files (udev);
usb_lock_device(udev);
/* choose and set the configuration. that registers the interfaces
* with the driver core, and lets usb device drivers bind to them.
*/
......@@ -1385,6 +1376,8 @@ int usb_new_device(struct usb_device *udev)
/* USB device state == configured ... usable */
usb_notify_add_device(udev);
usb_unlock_device(udev);
return 0;
fail:
......@@ -1872,11 +1865,8 @@ int usb_resume_device(struct usb_device *udev)
usb_unlock_device(udev);
/* rebind drivers that had no suspend() */
if (status == 0) {
usb_lock_all_devices();
if (status == 0)
bus_rescan_devices(&usb_bus_type);
usb_unlock_all_devices();
}
return status;
}
......@@ -1889,14 +1879,14 @@ static int remote_wakeup(struct usb_device *udev)
/* don't repeat RESUME sequence if this device
* was already woken up by some other task
*/
down(&udev->serialize);
usb_lock_device(udev);
if (udev->state == USB_STATE_SUSPENDED) {
dev_dbg(&udev->dev, "RESUME (wakeup)\n");
/* TRSMRCY = 10 msec */
msleep(10);
status = finish_device_resume(udev);
}
up(&udev->serialize);
usb_unlock_device(udev);
#endif
return status;
}
......@@ -1997,7 +1987,7 @@ static int hub_resume(struct usb_interface *intf)
if (!udev || status < 0)
continue;
down (&udev->serialize);
usb_lock_device(udev);
if (portstat & USB_PORT_STAT_SUSPEND)
status = hub_port_resume(hub, port1, udev);
else {
......@@ -2008,7 +1998,7 @@ static int hub_resume(struct usb_interface *intf)
hub_port_logical_disconnect(hub, port1);
}
}
up(&udev->serialize);
usb_unlock_device(udev);
}
}
#endif
......@@ -2573,7 +2563,6 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
* udev becomes globally accessible, although presumably
* no one will look at it until hdev is unlocked.
*/
down (&udev->serialize);
status = 0;
/* We mustn't add new devices if the parent hub has
......@@ -2597,7 +2586,6 @@ static void hub_port_connect_change(struct usb_hub *hub, int port1,
}
}
up (&udev->serialize);
if (status)
goto loop_disable;
......
......@@ -32,7 +32,6 @@
#include <linux/spinlock.h>
#include <linux/errno.h>
#include <linux/smp_lock.h>
#include <linux/rwsem.h>
#include <linux/usb.h>
#include <asm/io.h>
......@@ -49,8 +48,6 @@ const char *usbcore_name = "usbcore";
static int nousb; /* Disable USB when built into kernel image */
/* Not honored on modular build */
static DECLARE_RWSEM(usb_all_devices_rwsem);
/**
* usb_ifnum_to_if - get the interface object with a given interface number
......@@ -446,8 +443,6 @@ usb_alloc_dev(struct usb_device *parent, struct usb_bus *bus, unsigned port1)
dev->parent = parent;
INIT_LIST_HEAD(&dev->filelist);
init_MUTEX(&dev->serialize);
return dev;
}
......@@ -520,75 +515,20 @@ void usb_put_intf(struct usb_interface *intf)
/* USB device locking
*
* Although locking USB devices should be straightforward, it is
* complicated by the way the driver-model core works. When a new USB
* driver is registered or unregistered, the core will automatically
* probe or disconnect all matching interfaces on all USB devices while
* holding the USB subsystem writelock. There's no good way for us to
* tell which devices will be used or to lock them beforehand; our only
* option is to effectively lock all the USB devices.
*
* We do that by using a private rw-semaphore, usb_all_devices_rwsem.
* When locking an individual device you must first acquire the rwsem's
* readlock. When a driver is registered or unregistered the writelock
* must be held. These actions are encapsulated in the subroutines
* below, so all a driver needs to do is call usb_lock_device() and
* usb_unlock_device().
* USB devices and interfaces are locked using the semaphore in their
* embedded struct device. The hub driver guarantees that whenever a
* device is connected or disconnected, drivers are called with the
* USB device locked as well as their particular interface.
*
* Complications arise when several devices are to be locked at the same
* time. Only hub-aware drivers that are part of usbcore ever have to
* do this; nobody else needs to worry about it. The problem is that
* usb_lock_device() must not be called to lock a second device since it
* would acquire the rwsem's readlock reentrantly, leading to deadlock if
* another thread was waiting for the writelock. The solution is simple:
*
* When locking more than one device, call usb_lock_device()
* to lock the first one. Lock the others by calling
* down(&udev->serialize) directly.
*
* When unlocking multiple devices, use up(&udev->serialize)
* to unlock all but the last one. Unlock the last one by
* calling usb_unlock_device().
* do this; nobody else needs to worry about it. The rule for locking
* is simple:
*
* When locking both a device and its parent, always lock the
* the parent first.
*/
/**
* usb_lock_device - acquire the lock for a usb device structure
* @udev: device that's being locked
*
* Use this routine when you don't hold any other device locks;
* to acquire nested inner locks call down(&udev->serialize) directly.
* This is necessary for proper interaction with usb_lock_all_devices().
*/
void usb_lock_device(struct usb_device *udev)
{
down_read(&usb_all_devices_rwsem);
down(&udev->serialize);
}
/**
* usb_trylock_device - attempt to acquire the lock for a usb device structure
* @udev: device that's being locked
*
* Don't use this routine if you already hold a device lock;
* use down_trylock(&udev->serialize) instead.
* This is necessary for proper interaction with usb_lock_all_devices().
*
* Returns 1 if successful, 0 if contention.
*/
int usb_trylock_device(struct usb_device *udev)
{
if (!down_read_trylock(&usb_all_devices_rwsem))
return 0;
if (down_trylock(&udev->serialize)) {
up_read(&usb_all_devices_rwsem);
return 0;
}
return 1;
}
/**
* usb_lock_device_for_reset - cautiously acquire the lock for a
* usb device structure
......@@ -627,7 +567,7 @@ int usb_lock_device_for_reset(struct usb_device *udev,
}
}
while (!usb_trylock_device(udev)) {
while (usb_trylock_device(udev) != 0) {
/* If we can't acquire the lock after waiting one second,
* we're probably deadlocked */
......@@ -645,39 +585,6 @@ int usb_lock_device_for_reset(struct usb_device *udev,
return 1;
}
/**
* usb_unlock_device - release the lock for a usb device structure
* @udev: device that's being unlocked
*
* Use this routine when releasing the only device lock you hold;
* to release inner nested locks call up(&udev->serialize) directly.
* This is necessary for proper interaction with usb_lock_all_devices().
*/
void usb_unlock_device(struct usb_device *udev)
{
up(&udev->serialize);
up_read(&usb_all_devices_rwsem);
}
/**
* usb_lock_all_devices - acquire the lock for all usb device structures
*
* This is necessary when registering a new driver or probing a bus,
* since the driver-model core may try to use any usb_device.
*/
void usb_lock_all_devices(void)
{
down_write(&usb_all_devices_rwsem);
}
/**
* usb_unlock_all_devices - release the lock for all usb device structures
*/
void usb_unlock_all_devices(void)
{
up_write(&usb_all_devices_rwsem);
}
static struct usb_device *match_device(struct usb_device *dev,
u16 vendor_id, u16 product_id)
......@@ -700,10 +607,10 @@ static struct usb_device *match_device(struct usb_device *dev,
/* look through all of the children of this device */
for (child = 0; child < dev->maxchild; ++child) {
if (dev->children[child]) {
down(&dev->children[child]->serialize);
usb_lock_device(dev->children[child]);
ret_dev = match_device(dev->children[child],
vendor_id, product_id);
up(&dev->children[child]->serialize);
usb_unlock_device(dev->children[child]);
if (ret_dev)
goto exit;
}
......@@ -1300,10 +1207,7 @@ EXPORT_SYMBOL(usb_put_dev);
EXPORT_SYMBOL(usb_get_dev);
EXPORT_SYMBOL(usb_hub_tt_clear_buffer);
EXPORT_SYMBOL(usb_lock_device);
EXPORT_SYMBOL(usb_trylock_device);
EXPORT_SYMBOL(usb_lock_device_for_reset);
EXPORT_SYMBOL(usb_unlock_device);
EXPORT_SYMBOL(usb_driver_claim_interface);
EXPORT_SYMBOL(usb_driver_release_interface);
......
......@@ -16,9 +16,6 @@ extern int usb_get_device_descriptor(struct usb_device *dev,
extern char *usb_cache_string(struct usb_device *udev, int index);
extern int usb_set_configuration(struct usb_device *dev, int configuration);
extern void usb_lock_all_devices(void);
extern void usb_unlock_all_devices(void);
extern void usb_kick_khubd(struct usb_device *dev);
extern void usb_suspend_root_hub(struct usb_device *hdev);
extern void usb_resume_root_hub(struct usb_device *dev);
......
......@@ -372,7 +372,7 @@ done:
& ohci->hc_control)
== OHCI_USB_OPER
&& time_after (jiffies, ohci->next_statechange)
&& usb_trylock_device (hcd->self.root_hub)
&& usb_trylock_device (hcd->self.root_hub) == 0
) {
ohci_vdbg (ohci, "autosuspend\n");
(void) ohci_bus_suspend (hcd);
......
......@@ -329,8 +329,6 @@ struct usb_device {
struct usb_tt *tt; /* low/full speed dev, highspeed hub */
int ttport; /* device port on that tt hub */
struct semaphore serialize;
unsigned int toggle[2]; /* one bit for each endpoint
* ([0] = IN, [1] = OUT) */
......@@ -377,11 +375,12 @@ struct usb_device {
extern struct usb_device *usb_get_dev(struct usb_device *dev);
extern void usb_put_dev(struct usb_device *dev);
extern void usb_lock_device(struct usb_device *udev);
extern int usb_trylock_device(struct usb_device *udev);
/* USB device locking */
#define usb_lock_device(udev) down(&(udev)->dev.sem)
#define usb_unlock_device(udev) up(&(udev)->dev.sem)
#define usb_trylock_device(udev) down_trylock(&(udev)->dev.sem)
extern int usb_lock_device_for_reset(struct usb_device *udev,
struct usb_interface *iface);
extern void usb_unlock_device(struct usb_device *udev);
/* USB port reset for device reinitialization */
extern int usb_reset_device(struct usb_device *dev);
......
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