From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
To: Benjamin Gaignard <benjamin.gaignard@collabora.com>,
mchehab@kernel.org, tfiga@chromium.org
Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel@collabora.com
Subject: Re: [PATCH] media: usbtv: Remove useless locks in usbtv_video_free()
Date: Wed, 28 Feb 2024 12:33:16 +0100 [thread overview]
Message-ID: <19cdefd3-163b-41a1-b603-764aab4b5b90@xs4all.nl> (raw)
In-Reply-To: <b8400b7b-0716-4e8c-9ae5-f594778066c5@xs4all.nl>
On 28/02/2024 09:45, Hans Verkuil wrote:
> On 20/02/2024 09:06, Benjamin Gaignard wrote:
>> Remove locks calls in usbtv_video_free() because
>> are useless and may led to a deadlock as reported here:
>> https://syzkaller.appspot.com/x/bisect.txt?x=166dc872180000
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
>> Fixes: c838530d230b ("media: media videobuf2: Be more flexible on the number of queue stored buffers")
>
> Hmm, the code was really always wrong, it is just that before this commit
> it would only fail if you did a disconnect while streaming, and now it also
> fails if you disconnect when you are not streaming, so it is much more
> noticeable now.
>
> That should probably be explained better in the commit log. You could add a
> second Fixes line:
>
> Fixes: f3d27f34fdd7 ("[media] usbtv: Add driver for Fushicai USBTV007 video frame grabber")
>
> but I am not sure how useful that is.
>
>> ---
>> drivers/media/usb/usbtv/usbtv-video.c | 6 ------
>> 1 file changed, 6 deletions(-)
>>
>> diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c
>> index 62a583040cd4..96276358d116 100644
>> --- a/drivers/media/usb/usbtv/usbtv-video.c
>> +++ b/drivers/media/usb/usbtv/usbtv-video.c
>> @@ -963,15 +963,9 @@ int usbtv_video_init(struct usbtv *usbtv)
>>
>> void usbtv_video_free(struct usbtv *usbtv)
>> {
>> - mutex_lock(&usbtv->vb2q_lock);
>> - mutex_lock(&usbtv->v4l2_lock);
>> -
>> usbtv_stop(usbtv);
>
> This call should also be dropped...
>
>> vb2_video_unregister_device(&usbtv->vdev);
>
> ...since this function will call stop_streaming if streaming is in progress,
> which will call usbtv_stop with all the correct locks held.
With that change you can add my:
Tested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Regards,
Hans
>
> Regards,
>
> Hans
>
>> v4l2_device_disconnect(&usbtv->v4l2_dev);
>>
>> - mutex_unlock(&usbtv->v4l2_lock);
>> - mutex_unlock(&usbtv->vb2q_lock);
>> -
>> v4l2_device_put(&usbtv->v4l2_dev);
>> }
>
>
prev parent reply other threads:[~2024-02-28 11:33 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-20 8:06 [PATCH] media: usbtv: Remove useless locks in usbtv_video_free() Benjamin Gaignard
2024-02-20 10:42 ` Tomasz Figa
2024-02-28 8:45 ` Hans Verkuil
2024-02-28 11:33 ` Hans Verkuil [this message]
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