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author | Alan Stern <stern@rowland.harvard.edu> | 2010-01-08 12:56:19 -0500 |
---|---|---|
committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-03-02 14:54:08 -0800 |
commit | 62e299e61a6ffe8131fa85a984c3058b68586f5d (patch) | |
tree | d10709c5b5e6d280e1329c7ed4f30f990246893e /drivers/usb/core/devio.c | |
parent | 0f3dda9f7ff2db8dbf4d6fbab4d4438251446002 (diff) | |
download | op-kernel-dev-62e299e61a6ffe8131fa85a984c3058b68586f5d.zip op-kernel-dev-62e299e61a6ffe8131fa85a984c3058b68586f5d.tar.gz |
USB: change locking for device-level autosuspend
This patch (as1323) changes the locking requirements for
usb_autosuspend_device(), usb_autoresume_device(), and
usb_try_autosuspend_device(). This isn't a very important change;
mainly it's meant to make the locking more uniform.
The most tricky part of the patch involves changes to usbdev_open().
To avoid an ABBA locking problem, it was necessary to reduce the
region protected by usbfs_mutex. Since that mutex now protects only
against simultaneous open and remove, this posed no difficulty -- its
scope was larger than necessary.
And it turns out that usbfs_mutex is no longer needed in
usbdev_release() at all. The list of usbfs "ps" structures is now
protected by the device lock instead of by usbfs_mutex.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'drivers/usb/core/devio.c')
-rw-r--r-- | drivers/usb/core/devio.c | 40 |
1 files changed, 24 insertions, 16 deletions
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c index 431d172..825e0ab 100644 --- a/drivers/usb/core/devio.c +++ b/drivers/usb/core/devio.c @@ -654,19 +654,21 @@ static int usbdev_open(struct inode *inode, struct file *file) int ret; lock_kernel(); - /* Protect against simultaneous removal or release */ - mutex_lock(&usbfs_mutex); ret = -ENOMEM; ps = kmalloc(sizeof(struct dev_state), GFP_KERNEL); if (!ps) - goto out; + goto out_free_ps; ret = -ENODEV; + /* Protect against simultaneous removal or release */ + mutex_lock(&usbfs_mutex); + /* usbdev device-node */ if (imajor(inode) == USB_DEVICE_MAJOR) dev = usbdev_lookup_by_devt(inode->i_rdev); + #ifdef CONFIG_USB_DEVICEFS /* procfs file */ if (!dev) { @@ -678,13 +680,19 @@ static int usbdev_open(struct inode *inode, struct file *file) dev = NULL; } #endif - if (!dev || dev->state == USB_STATE_NOTATTACHED) - goto out; + mutex_unlock(&usbfs_mutex); + + if (!dev) + goto out_free_ps; + + usb_lock_device(dev); + if (dev->state == USB_STATE_NOTATTACHED) + goto out_unlock_device; + ret = usb_autoresume_device(dev); if (ret) - goto out; + goto out_unlock_device; - ret = 0; ps->dev = dev; ps->file = file; spin_lock_init(&ps->lock); @@ -702,14 +710,17 @@ static int usbdev_open(struct inode *inode, struct file *file) smp_wmb(); list_add_tail(&ps->list, &dev->filelist); file->private_data = ps; + usb_unlock_device(dev); snoop(&dev->dev, "opened by process %d: %s\n", task_pid_nr(current), current->comm); - out: - if (ret) { - kfree(ps); - usb_put_dev(dev); - } - mutex_unlock(&usbfs_mutex); + unlock_kernel(); + return ret; + + out_unlock_device: + usb_unlock_device(dev); + usb_put_dev(dev); + out_free_ps: + kfree(ps); unlock_kernel(); return ret; } @@ -724,10 +735,7 @@ static int usbdev_release(struct inode *inode, struct file *file) usb_lock_device(dev); usb_hub_release_all_ports(dev, ps); - /* Protect against simultaneous open */ - mutex_lock(&usbfs_mutex); list_del_init(&ps->list); - mutex_unlock(&usbfs_mutex); for (ifnum = 0; ps->ifclaimed && ifnum < 8*sizeof(ps->ifclaimed); ifnum++) { |