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HID: wiimote: fix FF deadlock 

The input core has an internal spinlock that is acquired during event
injection via input_event() and friends but also held during FF callbacks.
That means, there is no way to share a lock between event-injection and FF
handling. Unfortunately, this is what is required for wiimote state
tracking and what we do with state.lock and input->lock.

This deadlock can be triggered when using continuous data reporting and FF
on a wiimote device at the same time. I takes me at least 30m of
stress-testing to trigger it but users reported considerably shorter
times (http://bpaste.net/show/132504/) when using some gaming-console
emulators.

The real problem is that we have two copies of internal state, one in the
wiimote objects and the other in the input device. As the input-lock is
not supposed to be accessed from outside of input-core, we have no other
chance than offloading FF handling into a worker. This actually works
pretty nice and also allows to implictly merge fast rumble changes into a
single request.

Due to the 3-layered workers (rumble+queue+l2cap) this might reduce FF
responsiveness. Initial tests were fine so lets fix the race first and if
it turns out to be too slow we can always handle FF out-of-band and skip
the queue-worker.

Cc: <stable@vger.kernel.org> # 3.11+
Reported-by: Thomas Schneider
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
David Herrmann 2013-10-02 13:47:28 +02:00 committed by Jiri Kosina
parent 7da7cbbbeb
commit f50f9aabf3
2 changed files with 32 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
drivers/hid/hid-wiimote-modules.c
View File

@ -119,12 +119,22 @@ static const struct wiimod_ops wiimod_keys = {
* the rumble motor, this flag shouldn't be set.
*/
/* used by wiimod_rumble and wiipro_rumble */
static void wiimod_rumble_worker(struct work_struct *work)
{
struct wiimote_data *wdata = container_of(work, struct wiimote_data,
rumble_worker);
spin_lock_irq(&wdata->state.lock);
wiiproto_req_rumble(wdata, wdata->state.cache_rumble);
spin_unlock_irq(&wdata->state.lock);
}
static int wiimod_rumble_play(struct input_dev *dev, void *data,
struct ff_effect *eff)
{
struct wiimote_data *wdata = input_get_drvdata(dev);
__u8 value;
unsigned long flags;
/*
* The wiimote supports only a single rumble motor so if any magnitude
@ -137,9 +147,10 @@ static int wiimod_rumble_play(struct input_dev *dev, void *data,
else
value = 0;
spin_lock_irqsave(&wdata->state.lock, flags);
wiiproto_req_rumble(wdata, value);
spin_unlock_irqrestore(&wdata->state.lock, flags);
/* Locking state.lock here might deadlock with input_event() calls.
* schedule_work acts as barrier. Merging multiple changes is fine. */
wdata->state.cache_rumble = value;
schedule_work(&wdata->rumble_worker);
return 0;
}
@ -147,6 +158,8 @@ static int wiimod_rumble_play(struct input_dev *dev, void *data,
static int wiimod_rumble_probe(const struct wiimod_ops *ops,
struct wiimote_data *wdata)
{
INIT_WORK(&wdata->rumble_worker, wiimod_rumble_worker);
set_bit(FF_RUMBLE, wdata->input->ffbit);
if (input_ff_create_memless(wdata->input, NULL, wiimod_rumble_play))
return -ENOMEM;
@ -159,6 +172,8 @@ static void wiimod_rumble_remove(const struct wiimod_ops *ops,
{
unsigned long flags;
cancel_work_sync(&wdata->rumble_worker);
spin_lock_irqsave(&wdata->state.lock, flags);
wiiproto_req_rumble(wdata, 0);
spin_unlock_irqrestore(&wdata->state.lock, flags);
@ -1731,7 +1746,6 @@ static int wiimod_pro_play(struct input_dev *dev, void *data,
{
struct wiimote_data *wdata = input_get_drvdata(dev);
__u8 value;
unsigned long flags;
/*
* The wiimote supports only a single rumble motor so if any magnitude
@ -1744,9 +1758,10 @@ static int wiimod_pro_play(struct input_dev *dev, void *data,
else
value = 0;
spin_lock_irqsave(&wdata->state.lock, flags);
wiiproto_req_rumble(wdata, value);
spin_unlock_irqrestore(&wdata->state.lock, flags);
/* Locking state.lock here might deadlock with input_event() calls.
* schedule_work acts as barrier. Merging multiple changes is fine. */
wdata->state.cache_rumble = value;
schedule_work(&wdata->rumble_worker);
return 0;
}
@ -1756,6 +1771,8 @@ static int wiimod_pro_probe(const struct wiimod_ops *ops,
{
int ret, i;
INIT_WORK(&wdata->rumble_worker, wiimod_rumble_worker);
wdata->extension.input = input_allocate_device();
if (!wdata->extension.input)
return -ENOMEM;
@ -1817,12 +1834,13 @@ static void wiimod_pro_remove(const struct wiimod_ops *ops,
if (!wdata->extension.input)
return;
input_unregister_device(wdata->extension.input);
wdata->extension.input = NULL;
cancel_work_sync(&wdata->rumble_worker);
spin_lock_irqsave(&wdata->state.lock, flags);
wiiproto_req_rumble(wdata, 0);
spin_unlock_irqrestore(&wdata->state.lock, flags);
input_unregister_device(wdata->extension.input);
wdata->extension.input = NULL;
}
static const struct wiimod_ops wiimod_pro = {

4
drivers/hid/hid-wiimote.h
View File

@ -133,13 +133,15 @@ struct wiimote_state {
__u8 *cmd_read_buf;
__u8 cmd_read_size;
/* calibration data */
/* calibration/cache data */
__u16 calib_bboard[4][3];
__u8 cache_rumble;
};
struct wiimote_data {
struct hid_device *hdev;
struct input_dev *input;
struct work_struct rumble_worker;
struct led_classdev *leds[4];
struct input_dev *accel;
struct input_dev *ir;