[PATCH 3.18 053/150] HID: wacom: fix freeze on open when autosuspend is on

Greg Kroah-Hartman
2015-01-14T07:28:40Z

From: Benjamin Tissoires <benjamin.tissoires@redhat.com>

commit dff674168878fe7b6d8b9ad60d62295ec517de79 upstream.

Since the conversion from USB to HID (in v3.17), some people reported a
freeze on boot with the wacom driver. Hans managed to get a stacktrace:

[ 240.272331] Call Trace:
[ 240.272338] [<ffffffff813de7b9>] ? usb_hcd_submit_urb+0xa9/0xb10
[ 240.272347] [<ffffffff81555579>] schedule+0x29/0x70
[ 240.272355] [<ffffffff815559e6>] schedule_preempt_disabled+0x16/0x20
[ 240.272363] [<ffffffff81557365>] __mutex_lock_slowpath+0xe5/0x230
[ 240.272372] [<ffffffff815574c7>] mutex_lock+0x17/0x30
[ 240.272380] [<ffffffffa063c1d2>] wacom_resume+0x22/0x50 [wacom]
[ 240.272396] [<ffffffffa01aea8a>] hid_resume_common+0xba/0x110 [usbhid]
[ 240.272404] [<ffffffff813e5890>] ? usb_runtime_suspend+0x80/0x80
[ 240.272417] [<ffffffffa01aeb1d>] hid_resume+0x3d/0x70 [usbhid]
[ 240.272425] [<ffffffff813e44a6>] usb_resume_interface.isra.6+0xb6/0x120
[ 240.272432] [<ffffffff813e4774>] usb_resume_both+0x74/0x140
[ 240.272439] [<ffffffff813e58aa>] usb_runtime_resume+0x1a/0x20
[ 240.272446] [<ffffffff813b1912>] __rpm_callback+0x32/0x70
[ 240.272453] [<ffffffff813b1976>] rpm_callback+0x26/0xa0
[ 240.272460] [<ffffffff813b2d71>] rpm_resume+0x4b1/0x690
[ 240.272468] [<ffffffff812ab992>] ? radix_tree_lookup_slot+0x22/0x50
[ 240.272475] [<ffffffff813b2c1a>] rpm_resume+0x35a/0x690
[ 240.272482] [<ffffffff8116e9c9>] ? zone_statistics+0x89/0xa0
[ 240.272489] [<ffffffff813b2f90>] __pm_runtime_resume+0x40/0x60
[ 240.272497] [<ffffffff813e4272>] usb_autopm_get_interface+0x22/0x60
[ 240.272509] [<ffffffffa01ae8d9>] usbhid_open+0x59/0xe0 [usbhid]
[ 240.272517] [<ffffffffa063ac85>] wacom_open+0x35/0x50 [wacom]
[ 240.272525] [<ffffffff813f37b9>] input_open_device+0x79/0xa0
[ 240.272534] [<ffffffffa048d1c1>] evdev_open+0x1b1/0x200 [evdev]
[ 240.272543] [<ffffffff811c899e>] chrdev_open+0xae/0x1f0
[ 240.272549] [<ffffffff811c88f0>] ? cdev_put+0x30/0x30
[ 240.272556] [<ffffffff811c17e2>] do_dentry_open+0x1d2/0x320
[ 240.272562] [<ffffffff811c1cd1>] finish_open+0x31/0x50
[ 240.272571] [<ffffffff811d2202>] do_last.isra.36+0x652/0xe50
[ 240.272579] [<ffffffff811d2ac7>] path_openat+0xc7/0x6f0
[ 240.272586] [<ffffffff811cf012>] ? final_putname+0x22/0x50
[ 240.272594] [<ffffffff811d42d2>] ? user_path_at_empty+0x72/0xd0
[ 240.272602] [<ffffffff811d43fd>] do_filp_open+0x4d/0xc0
[...]

So here, wacom_open is called, and then wacom_resume is called by the
PM system. However, wacom_open already took the lock when wacom_resume
tries to get it. Freeze.

A little bit of history shows that this already happened in the past
- commit f6cd378372bf ("Input: wacom - fix runtime PM related deadlock"),
and the solution was to call first the PM function before taking the lock.

The lock was introduced in commit commit e722409445fb ("Input: wacom -
implement suspend and autosuspend") when the autosuspend feature has
been added. Given that usbhid already takes care of this very same
locking between suspend/resume, I think we can simply kill the lock
in open/close.

The lock is now used also with LEDs, so we can not remove it completely.

Reported-by: Hans Spath <inbox-546@hans-spath.de>
Tested-by: Hans Spath <inbox-546@hans-spath.de>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/hid/wacom_sys.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)

--- a/drivers/hid/wacom_sys.c
+++ b/drivers/hid/wacom_sys.c
@@ -70,22 +70,15 @@ static int wacom_raw_event(struct hid_de
static int wacom_open(struct input_dev *dev)
{
struct wacom *wacom = input_get_drvdata(dev);
- int retval;

- mutex_lock(&wacom->lock);
- retval = hid_hw_open(wacom->hdev);
- mutex_unlock(&wacom->lock);
-
- return retval;
+ return hid_hw_open(wacom->hdev);
}

static void wacom_close(struct input_dev *dev)
{
struct wacom *wacom = input_get_drvdata(dev);

- mutex_lock(&wacom->lock);
hid_hw_close(wacom->hdev);
- mutex_unlock(&wacom->lock);
}

/*