Hi Laurent, On 10/10/2024 20:23, Laurent Pinchart wrote: > Hi Hans, > > On Mon, Oct 07, 2024 at 04:53:30PM +0200, Hans Verkuil wrote: >> On 07/10/2024 16:44, Laurent Pinchart wrote: >>> On Mon, Oct 07, 2024 at 09:46:47AM +0200, Hans Verkuil wrote: >>>> Hi Laurent, >>>> >>>> Just a reminder: I have extensively reviewed this patch here: >>>> >>>> https://lore.kernel.org/linux-media/f4c49ccf-9dc9-475a-8fc9-4ef4c85a729a@xxxxxxxxx/ >>>> >>>> and here (specifically checking for mmap() races): >>>> >>>> https://lore.kernel.org/linux-media/1a10530f-b4bb-4244-84ff-1f2365ae9b23@xxxxxxxxx/ >>>> >>>> To the best of my ability I believe this patch is correct. >>>> >>>> Unless you have any additional concerns I plan to take this patch as a fix for >>>> v6.12 on Monday next week. >>> >>> I thought we had an agreement that I could submit an alternative fix for >>> v6.12. Can you therefore delay merging this patch until v6.12-rc6 ? >> >> Correct, if there is indeed something wrong with this patch and an alternative >> fix is needed (or at least should be considered). >> >> But I see nothing wrong with this patch after careful analysis. If you disagree >> with my analysis, and you think I missed a possible race condition, then that's >> a reason to wait for a better fix. Otherwise there is no point in waiting any longer. > > I'm in Montréal this week for the GStreamer conference and XDC. I'll > reply to your last e-mail early next week, let's make a decision then. > Surely this can wait until -rc4 before being merged ? Sure, no problem. Enjoy Montréal! Hans > >>>> Alternatively, you can make a PR for 6.12 with this patch that I can pull from. >>>> >>>> Regards, >>>> >>>> Hans >>>> >>>> On 26/09/2024 07:59, Ricardo Ribalda wrote: >>>>> uvc_unregister_video() can be called asynchronously from >>>>> uvc_disconnect(). If the device is still streaming when that happens, a >>>>> plethora of race conditions can occur. >>>>> >>>>> Make sure that the device has stopped streaming before exiting this >>>>> function. >>>>> >>>>> If the user still holds handles to the driver's file descriptors, any >>>>> ioctl will return -ENODEV from the v4l2 core. >>>>> >>>>> This change makes uvc more consistent with the rest of the v4l2 drivers >>>>> using the vb2_fop_* and vb2_ioctl_* helpers. >>>>> >>>>> Reviewed-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx> >>>>> Suggested-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx> >>>>> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx> >>>>> --- >>>>> This patch was part of the series: >>>>> https://patchwork.linuxtv.org/project/linux-media/list/?series=13064 >>>>> >>>>> Moved out from it to ease the review. >>>>> --- >>>>> drivers/media/usb/uvc/uvc_driver.c | 32 +++++++++++++++++++++++++++++++- >>>>> 1 file changed, 31 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c >>>>> index f0febdc08c2d..bee150b852e4 100644 >>>>> --- a/drivers/media/usb/uvc/uvc_driver.c >>>>> +++ b/drivers/media/usb/uvc/uvc_driver.c >>>>> @@ -1919,11 +1919,41 @@ static void uvc_unregister_video(struct uvc_device *dev) >>>>> struct uvc_streaming *stream; >>>>> >>>>> list_for_each_entry(stream, &dev->streams, list) { >>>>> + /* Nothing to do here, continue. */ >>>>> if (!video_is_registered(&stream->vdev)) >>>>> continue; >>>>> >>>>> + /* >>>>> + * For stream->vdev we follow the same logic as: >>>>> + * vb2_video_unregister_device(). >>>>> + */ >>>>> + >>>>> + /* 1. Take a reference to vdev */ >>>>> + get_device(&stream->vdev.dev); >>>>> + >>>>> + /* 2. Ensure that no new ioctls can be called. */ >>>>> video_unregister_device(&stream->vdev); >>>>> - video_unregister_device(&stream->meta.vdev); >>>>> + >>>>> + /* 3. Wait for old ioctls to finish. */ >>>>> + mutex_lock(&stream->mutex); >>>>> + >>>>> + /* 4. Stop streaming. */ >>>>> + uvc_queue_release(&stream->queue); >>>>> + >>>>> + mutex_unlock(&stream->mutex); >>>>> + >>>>> + put_device(&stream->vdev.dev); >>>>> + >>>>> + /* >>>>> + * For stream->meta.vdev we can directly call: >>>>> + * vb2_video_unregister_device(). >>>>> + */ >>>>> + vb2_video_unregister_device(&stream->meta.vdev); >>>>> + >>>>> + /* >>>>> + * Now both vdevs are not streaming and all the ioctls will >>>>> + * return -ENODEV. >>>>> + */ >>>>> >>>>> uvc_debugfs_cleanup_stream(stream); >>>>> } >>>>> >>>>> --- >>>>> base-commit: 81ee62e8d09ee3c7107d11c8bbfd64073ab601ad >>>>> change-id: 20240926-uvc_stop_streaming-6e9fd20e97bc >
