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SubjectRe: [PATCH] usb: gadget: composite: split spinlock to avoid recursion
Date
On 19-11-12 10:33:18, Michael Olbrich wrote:
> 'delayed_status' and 'deactivations' are used completely independent but
> they share the same spinlock. This can result in spinlock recursion:
>
> BUG: spinlock recursion on CPU#1, uvc-gadget/322
> lock: 0xffffffc0570364e0, .magic: dead4ead, .owner: uvc-gadget/322, .owner_cpu: 1
> CPU: 1 PID: 322 Comm: uvc-gadget Tainted: G C O 5.3.0-20190916-1+ #55
> Hardware name: XXXXX (DT)
> Call trace:
> dump_backtrace+0x0/0x178
> show_stack+0x24/0x30
> dump_stack+0xc0/0x104
> spin_dump+0x90/0xa0
> do_raw_spin_lock+0xd8/0x108
> _raw_spin_lock_irqsave+0x40/0x50
> composite_disconnect+0x2c/0x80
> usb_gadget_disconnect+0x84/0x150
> usb_gadget_deactivate+0x64/0x120
> usb_function_deactivate+0x70/0x80
> uvc_function_disconnect+0x20/0x58
> uvc_v4l2_release+0x34/0x90
> v4l2_release+0xbc/0xf0
> __fput+0xb0/0x218
> ____fput+0x20/0x30
> task_work_run+0xa0/0xd0
> do_notify_resume+0x2f4/0x340
> work_pending+0x8/0x14
>
> Fix this by using separate spinlocks.

This issue may be introduced by 0a55187a1ec8c ("USB: gadget core: Issue
->disconnect() callback from usb_gadget_disconnect()"), which adds
gadget's disconnect at usb_gadget_disconnect. Add Alan, if he is Ok
with your patch, you may cc to stable tree.

>
> Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>
> ---
> drivers/usb/gadget/composite.c | 9 +++++----
> drivers/usb/gadget/configfs.c | 1 +
> include/linux/usb/composite.h | 4 +++-
> 3 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/usb/gadget/composite.c b/drivers/usb/gadget/composite.c
> index 76883ff4f5bb..35c792e5b408 100644
> --- a/drivers/usb/gadget/composite.c
> +++ b/drivers/usb/gadget/composite.c
> @@ -346,14 +346,14 @@ int usb_function_deactivate(struct usb_function *function)
> unsigned long flags;
> int status = 0;
>
> - spin_lock_irqsave(&cdev->lock, flags);
> + spin_lock_irqsave(&cdev->deactivations_lock, flags);
>
> if (cdev->deactivations == 0)
> status = usb_gadget_deactivate(cdev->gadget);
> if (status == 0)
> cdev->deactivations++;
>
> - spin_unlock_irqrestore(&cdev->lock, flags);
> + spin_unlock_irqrestore(&cdev->deactivations_lock, flags);
> return status;
> }
> EXPORT_SYMBOL_GPL(usb_function_deactivate);
> @@ -374,7 +374,7 @@ int usb_function_activate(struct usb_function *function)
> unsigned long flags;
> int status = 0;
>
> - spin_lock_irqsave(&cdev->lock, flags);
> + spin_lock_irqsave(&cdev->deactivations_lock, flags);
>
> if (WARN_ON(cdev->deactivations == 0))
> status = -EINVAL;
> @@ -384,7 +384,7 @@ int usb_function_activate(struct usb_function *function)
> status = usb_gadget_activate(cdev->gadget);
> }
>
> - spin_unlock_irqrestore(&cdev->lock, flags);
> + spin_unlock_irqrestore(&cdev->deactivations_lock, flags);
> return status;
> }
> EXPORT_SYMBOL_GPL(usb_function_activate);
> @@ -2196,6 +2196,7 @@ static int composite_bind(struct usb_gadget *gadget,
> return status;
>
> spin_lock_init(&cdev->lock);
> + spin_lock_init(&cdev->deactivations_lock);
> cdev->gadget = gadget;
> set_gadget_data(gadget, cdev);
> INIT_LIST_HEAD(&cdev->configs);
> diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
> index 025129942894..45f717fcdb89 100644
> --- a/drivers/usb/gadget/configfs.c
> +++ b/drivers/usb/gadget/configfs.c
> @@ -521,6 +521,7 @@ static const struct config_item_type gadget_root_type = {
> static void composite_init_dev(struct usb_composite_dev *cdev)
> {
> spin_lock_init(&cdev->lock);
> + spin_lock_init(&cdev->deactivations_lock);
> INIT_LIST_HEAD(&cdev->configs);
> INIT_LIST_HEAD(&cdev->gstrings);
> }
> diff --git a/include/linux/usb/composite.h b/include/linux/usb/composite.h
> index 8675e145ea8b..86eb6f2c03ac 100644
> --- a/include/linux/usb/composite.h
> +++ b/include/linux/usb/composite.h
> @@ -505,8 +505,10 @@ struct usb_composite_dev {
> */
> int delayed_status;
>
> - /* protects deactivations and delayed_status counts*/
> + /* protects delayed_status counts*/
> spinlock_t lock;

In fact, this lock is used many places, not only at setup delayed cases.
You may change comments or delete the comments.

> + /* protects deactivations counts*/

Add one space after 'counts'.

> + spinlock_t deactivations_lock;
>

--

Thanks,
Peter Chen
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