Commit f6cd3783 authored Oct 04, 2010 by Dmitry Torokhov

Input: wacom - fix runtime PM related deadlock



When runtime PM is enabled by default for input devices, X hangs in
wacom open:
[<ffffffff814a00ea>] mutex_lock+0x1a/0x40
[<ffffffffa02bc94b>] wacom_resume+0x3b/0x90 [wacom]
[<ffffffff81327a32>] usb_resume_interface+0xd2/0x190
[<ffffffff81327b5d>] usb_resume_both+0x6d/0x110
[<ffffffff81327c24>] usb_runtime_resume+0x24/0x40
[<ffffffff8130a2cf>] __pm_runtime_resume+0x26f/0x450
[<ffffffff8130a23a>] __pm_runtime_resume+0x1da/0x450
[<ffffffff8130a53a>] pm_runtime_resume+0x2a/0x50
[<ffffffff81328176>] usb_autopm_get_interface+0x26/0x60
[<ffffffffa02bc626>] wacom_open+0x36/0x90 [wacom]

wacom_open() takes wacom->lock and calls usb_autopm_get_interface(),
which in turn calls wacom_resume() which tries to acquire the lock
again.

The fix is to call usb_autopm_get_interface() first, before we take
the lock.

Since we do not do usb_autopm_put_interface() until wacom_close()
is called runtime PM is effectively disabled for the driver, however
changing it now would risk regressions so the complete fix will
have to wait till the next merge window.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Oliver Neukum <oneukum@suse.de>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

parent d2520a42

drivers/input/tablet/wacom_sys.c

+12 −11

Original line number	Diff line number	Diff line
		@@ -103,27 +103,26 @@ static void wacom_sys_irq(struct urb *urb)
		static int wacom_open(struct input_dev *dev)
		{
		struct wacom *wacom = input_get_drvdata(dev);
		int retval = 0;

		mutex_lock(&wacom->lock);

		wacom->irq->dev = wacom->usbdev;

		if (usb_autopm_get_interface(wacom->intf) < 0) {
		mutex_unlock(&wacom->lock);
		if (usb_autopm_get_interface(wacom->intf) < 0)
		return -EIO;
		}

		mutex_lock(&wacom->lock);

		if (usb_submit_urb(wacom->irq, GFP_KERNEL)) {
		usb_autopm_put_interface(wacom->intf);
		mutex_unlock(&wacom->lock);
		return -EIO;
		retval = -EIO;
		goto out;
		}

		wacom->open = true;
		wacom->intf->needs_remote_wakeup = 1;

		out:
		mutex_unlock(&wacom->lock);
		return 0;
		if (retval)
		usb_autopm_put_interface(wacom->intf);
		return retval;
		}

		static void wacom_close(struct input_dev *dev)
		@@ -135,6 +134,8 @@ static void wacom_close(struct input_dev *dev)
		wacom->open = false;
		wacom->intf->needs_remote_wakeup = 0;
		mutex_unlock(&wacom->lock);

		usb_autopm_put_interface(wacom->intf);
		}

		static int wacom_parse_hid(struct usb_interface intf, struct hid_descriptor hid_desc,