diff options
| author | Ioan-Adrian Ratiu | 2015-11-20 22:19:02 +0200 |
|---|---|---|
| committer | Jiri Kosina | 2015-12-01 17:35:10 +0100 |
| commit | e470127e9606b1fa151c4184243e61296d1e0c0f (patch) | |
| tree | ab160824865a4badf17f7257924e7d0d9b622c55 /drivers/hid | |
| parent | 92529623d242cea4440958d7bcebdf291f4ab15e (diff) | |
HID: usbhid: fix recursive deadlock
The critical section protected by usbhid->lock in hid_ctrl() is too
big and because of this it causes a recursive deadlock. "Too big" means
the case statement and the call to hid_input_report() do not need to be
protected by the spinlock (no URB operations are done inside them).
The deadlock happens because in certain rare cases drivers try to grab
the lock while handling the ctrl irq which grabs the lock before them
as described above. For example newer wacom tablets like 056a:033c try
to reschedule proximity reads from wacom_intuos_schedule_prox_event()
calling hid_hw_request() -> usbhid_request() -> usbhid_submit_report()
which tries to grab the usbhid lock already held by hid_ctrl().
There are two ways to get out of this deadlock:
1. Make the drivers work "around" the ctrl critical region, in the
wacom case for ex. by delaying the scheduling of the proximity read
request itself to a workqueue.
2. Shrink the critical region so the usbhid lock protects only the
instructions which modify usbhid state, calling hid_input_report()
with the spinlock unlocked, allowing the device driver to grab the
lock first, finish and then grab the lock afterwards in hid_ctrl().
This patch implements the 2nd solution.
Signed-off-by: Ioan-Adrian Ratiu <adi@adirat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'drivers/hid')
| -rw-r--r-- | drivers/hid/usbhid/hid-core.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c index 19a4364c9085..ad71160b9ea4 100644 --- a/drivers/hid/usbhid/hid-core.c +++ b/drivers/hid/usbhid/hid-core.c @@ -477,8 +477,6 @@ static void hid_ctrl(struct urb *urb) struct usbhid_device *usbhid = hid->driver_data; int unplug = 0, status = urb->status; - spin_lock(&usbhid->lock); - switch (status) { case 0: /* success */ if (usbhid->ctrl[usbhid->ctrltail].dir == USB_DIR_IN) @@ -498,6 +496,8 @@ static void hid_ctrl(struct urb *urb) hid_warn(urb->dev, "ctrl urb status %d received\n", status); } + spin_lock(&usbhid->lock); + if (unplug) { usbhid->ctrltail = usbhid->ctrlhead; } else { |