| Message ID | 1454508245-1757-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/drivers/hid/usbhid/hid-core.c b/drivers/hid/usbhid/hid-core.c index b22e5c4e5448..421187ba053a 100644 --- a/drivers/hid/usbhid/hid-core.c +++ b/drivers/hid/usbhid/hid-core.c @@ -492,8 +492,6 @@ 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) @@ -513,6 +511,8 @@ 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 {
This is a note to let you know that I have just added a patch titled HID: usbhid: fix recursive deadlock to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue This patch is scheduled to be released in version 3.16.7-ckt24. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.16.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Luis ---8<------------------------------------------------------------ From 9e9d8b71d01a0a69a6f281b33b79be95d0ea4601 Mon Sep 17 00:00:00 2001 From: Ioan-Adrian Ratiu <adi@adirat.com> Date: Fri, 20 Nov 2015 22:19:02 +0200 Subject: HID: usbhid: fix recursive deadlock commit e470127e9606b1fa151c4184243e61296d1e0c0f upstream. 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> Cc: Jason Gerecke <killertofu@gmail.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- drivers/hid/usbhid/hid-core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)