2021-08-02 22:57:53

by Salah Triki

Subject: [PATCH] sound: usb: get lock before calling usb_enable_autosuspend()

Based on the documentation of usb_enable_autosuspend(), the
caller must hold udev's device lock.

Signed-off-by: Salah Triki <[email protected]>
---
sound/usb/card.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 2f6a62416c05..9290ba0acd5f 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -907,8 +907,13 @@ static void usb_audio_disconnect(struct usb_interface *intf)
}
}

- if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND)
- usb_enable_autosuspend(interface_to_usbdev(intf));
+ if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND) {
+ struct usb_device *udev = interface_to_usbdev(intf);
+
+ usb_lock_device(udev);
+ usb_enable_autosuspend(udev);
+ usb_unlock_device(udev);
+ }

chip->num_interfaces--;
if (chip->num_interfaces <= 0) {
--
2.25.1

2021-08-03 07:42:33

by Takashi Iwai

Subject: Re: [PATCH] sound: usb: get lock before calling usb_enable_autosuspend()

On Tue, 03 Aug 2021 00:53:39 +0200,
Salah Triki wrote:
>
> Based on the documentation of usb_enable_autosuspend(), the
> caller must hold udev's device lock.

The device lock is already held in the caller side (in the driver
core), hence this change will lead to a deadlock.


thanks,

Takashi

>
> Signed-off-by: Salah Triki <[email protected]>
> ---
> sound/usb/card.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/sound/usb/card.c b/sound/usb/card.c
> index 2f6a62416c05..9290ba0acd5f 100644
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -907,8 +907,13 @@ static void usb_audio_disconnect(struct usb_interface *intf)
> }
> }
>
> - if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND)
> - usb_enable_autosuspend(interface_to_usbdev(intf));
> + if (chip->quirk_type & QUIRK_SETUP_DISABLE_AUTOSUSPEND) {
> + struct usb_device *udev = interface_to_usbdev(intf);
> +
> + usb_lock_device(udev);
> + usb_enable_autosuspend(udev);
> + usb_unlock_device(udev);
> + }
>
> chip->num_interfaces--;
> if (chip->num_interfaces <= 0) {
> --
> 2.25.1
>