From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from perceval.ideasonboard.com (perceval.ideasonboard.com [213.167.242.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4DD7B28D829; Thu, 24 Jul 2025 12:08:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=213.167.242.64 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753358927; cv=none; b=t9phCCTBx8gcw0AOxFEHIonniDbLmRKwZJbYdRpr6e3IM50KXc4G0rx5EmlvQVS6KeaDntR+u7wYHqiJy5AJWNminfajF2/46x1JpjF8AfF8BZ1CfkoEOTVPgcTCn0Um9Py03FeQAy+lkkZtK7SYRyuI7HmhBwiCNW8gB9gDtAE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753358927; c=relaxed/simple; bh=tonx440e4m3Mz4pug7QeKTvAF5+t3TwXJE9O5zha0C4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CJahs9yN58o0UugM52qE0zSNioD8FMqCwEUszBzss9HWICWZWIDtXt1VdNZ238rWZWV3KE/q1E3ctMVVyxsGJjYCH8bp1ZGsh1zrRxLc3E91zwxuXJq15f0HMl7+g+B6Coto8JpyXr41SqK/4rKaWtdPkptGk+6joomEfup6nZg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com; spf=pass smtp.mailfrom=ideasonboard.com; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b=Ox+JGQYq; arc=none smtp.client-ip=213.167.242.64 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=ideasonboard.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=ideasonboard.com header.i=@ideasonboard.com header.b="Ox+JGQYq" Received: from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi [81.175.209.231]) by perceval.ideasonboard.com (Postfix) with UTF8SMTPSA id 983C2C70; Thu, 24 Jul 2025 14:08:04 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1753358884; bh=tonx440e4m3Mz4pug7QeKTvAF5+t3TwXJE9O5zha0C4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Ox+JGQYqQJ/FELsU8O2jrVL06WQImx6W87uFMfRWglijjMPpWG4ApE4B/2S+YzJI2 oH9e6gxn6y1iU3VcsnQG1O9S4tbUU4T4Qc3dlYmqLYV9BTjM63w4xarC/alDno9IAe xZZPxbFvi4q7GtbXybCdfhuGRzamK+Xiq7I0+OF4= Date: Thu, 24 Jul 2025 15:08:40 +0300 From: Laurent Pinchart To: Ricardo Ribalda Cc: Hans de Goede , Mauro Carvalho Chehab , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] media: uvcvideo: Drop stream->mutex Message-ID: <20250724120840.GL11202@pendragon.ideasonboard.com> References: <20250717-uvc-onelocksless-v1-1-91a1b834186a@chromium.org> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20250717-uvc-onelocksless-v1-1-91a1b834186a@chromium.org> Hi Ricardo, Thank you for the patch. On Thu, Jul 17, 2025 at 07:56:45AM +0000, Ricardo Ribalda wrote: > Since commit c93d73c9c2cf ("media: uvcvideo: Use vb2 ioctl and fop > helpers"), the IOCTLs are serialized. Due to this there is no more need > to protect ctrl, cur_format or cur_frame from concurrent access. > > Drop stream->mutex after thanking it for years of good service. > > Use this opportunity to do fix some CodeStyle. Is that about the following change only: - if (format == NULL || frame == NULL) { + if (!format || !frame) or is there something else I missed ? > > Signed-off-by: Ricardo Ribalda > --- > drivers/media/usb/uvc/uvc_driver.c | 4 ---- > drivers/media/usb/uvc/uvc_metadata.c | 8 ++------ > drivers/media/usb/uvc/uvc_v4l2.c | 39 ++++++++---------------------------- > drivers/media/usb/uvc/uvcvideo.h | 6 ------ > 4 files changed, 10 insertions(+), 47 deletions(-) > > diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c > index 775bede0d93d9b3e5391914aa395326d3de6a3b1..3039e6a533b82dd917050d416c9ced8756d69170 100644 > --- a/drivers/media/usb/uvc/uvc_driver.c > +++ b/drivers/media/usb/uvc/uvc_driver.c > @@ -183,8 +183,6 @@ static void uvc_stream_delete(struct uvc_streaming *stream) > if (stream->async_wq) > destroy_workqueue(stream->async_wq); > > - mutex_destroy(&stream->mutex); > - > usb_put_intf(stream->intf); > > kfree(stream->formats); > @@ -201,8 +199,6 @@ static struct uvc_streaming *uvc_stream_new(struct uvc_device *dev, > if (stream == NULL) > return NULL; > > - mutex_init(&stream->mutex); > - > stream->dev = dev; > stream->intf = usb_get_intf(intf); > stream->intfnum = intf->cur_altsetting->desc.bInterfaceNumber; > diff --git a/drivers/media/usb/uvc/uvc_metadata.c b/drivers/media/usb/uvc/uvc_metadata.c > index 229e08ff323eed9129d835b24ea2e8085bb713b8..d1d4fade634bd3f8b12bbaa75388db42aecc25ea 100644 > --- a/drivers/media/usb/uvc/uvc_metadata.c > +++ b/drivers/media/usb/uvc/uvc_metadata.c > @@ -100,14 +100,10 @@ static int uvc_meta_v4l2_set_format(struct file *file, void *fh, > * Metadata buffers would still be perfectly parseable, but it's more > * consistent and cleaner to disallow that. > */ > - mutex_lock(&stream->mutex); > - > if (vb2_is_busy(&stream->meta.queue.queue)) > - ret = -EBUSY; > - else > - stream->meta.format = fmt->dataformat; > + return -EBUSY; > > - mutex_unlock(&stream->mutex); > + stream->meta.format = fmt->dataformat; > > return ret; return 0; > } > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c > index 160f9cf6e6dbdbf39e3eff56a5d5ea1d977fbe22..d7be4d59f0c73b983aa01321f4acc8f8bf6e83ef 100644 > --- a/drivers/media/usb/uvc/uvc_v4l2.c > +++ b/drivers/media/usb/uvc/uvc_v4l2.c > @@ -329,14 +329,12 @@ static int uvc_v4l2_try_format(struct uvc_streaming *stream, > * developers test their webcams with the Linux driver as well as with > * the Windows driver). > */ > - mutex_lock(&stream->mutex); > if (stream->dev->quirks & UVC_QUIRK_PROBE_EXTRAFIELDS) > probe->dwMaxVideoFrameSize = > stream->ctrl.dwMaxVideoFrameSize; > > /* Probe the device. */ > ret = uvc_probe_video(stream, probe); > - mutex_unlock(&stream->mutex); > if (ret < 0) > return ret; > > @@ -395,19 +393,15 @@ static int uvc_ioctl_g_fmt(struct file *file, void *fh, > struct uvc_streaming *stream = handle->stream; > const struct uvc_format *format; > const struct uvc_frame *frame; > - int ret = 0; > > if (fmt->type != stream->type) > return -EINVAL; > > - mutex_lock(&stream->mutex); > format = stream->cur_format; > frame = stream->cur_frame; > > - if (format == NULL || frame == NULL) { > - ret = -EINVAL; > - goto done; > - } > + if (!format || !frame) > + return -EINVAL; > > fmt->fmt.pix.pixelformat = format->fcc; > fmt->fmt.pix.width = frame->wWidth; > @@ -419,9 +413,7 @@ static int uvc_ioctl_g_fmt(struct file *file, void *fh, > fmt->fmt.pix.xfer_func = format->xfer_func; > fmt->fmt.pix.ycbcr_enc = format->ycbcr_enc; > > -done: > - mutex_unlock(&stream->mutex); > - return ret; > + return 0; > } > > static int uvc_ioctl_s_fmt(struct file *file, void *fh, > @@ -441,19 +433,14 @@ static int uvc_ioctl_s_fmt(struct file *file, void *fh, > if (ret < 0) > return ret; > > - mutex_lock(&stream->mutex); > - if (vb2_is_busy(&stream->queue.queue)) { > - ret = -EBUSY; > - goto done; > - } > + if (vb2_is_busy(&stream->queue.queue)) > + return -EBUSY; > > stream->ctrl = probe; > stream->cur_format = format; > stream->cur_frame = frame; > > -done: > - mutex_unlock(&stream->mutex); > - return ret; > + return 0; > } > > static int uvc_ioctl_g_parm(struct file *file, void *fh, > @@ -466,9 +453,7 @@ static int uvc_ioctl_g_parm(struct file *file, void *fh, > if (parm->type != stream->type) > return -EINVAL; > > - mutex_lock(&stream->mutex); > numerator = stream->ctrl.dwFrameInterval; > - mutex_unlock(&stream->mutex); > You can drop the blank line here. > denominator = 10000000; > v4l2_simplify_fraction(&numerator, &denominator, 8, 333); > @@ -519,12 +504,9 @@ static int uvc_ioctl_s_parm(struct file *file, void *fh, > uvc_dbg(stream->dev, FORMAT, "Setting frame interval to %u/%u (%u)\n", > timeperframe.numerator, timeperframe.denominator, interval); > > - mutex_lock(&stream->mutex); > Double blank line. > - if (uvc_queue_streaming(&stream->queue)) { > - mutex_unlock(&stream->mutex); > + if (uvc_queue_streaming(&stream->queue)) > return -EBUSY; > - } > > format = stream->cur_format; > frame = stream->cur_frame; > @@ -556,14 +538,11 @@ static int uvc_ioctl_s_parm(struct file *file, void *fh, > > /* Probe the device with the new settings. */ > ret = uvc_probe_video(stream, &probe); > - if (ret < 0) { > - mutex_unlock(&stream->mutex); > + if (ret < 0) > return ret; > - } > > stream->ctrl = probe; > stream->cur_frame = frame; > - mutex_unlock(&stream->mutex); > > /* Return the actual frame period. */ > timeperframe.numerator = probe.dwFrameInterval; > @@ -941,10 +920,8 @@ static int uvc_ioctl_g_selection(struct file *file, void *fh, > > sel->r.left = 0; > sel->r.top = 0; > - mutex_lock(&stream->mutex); > sel->r.width = stream->cur_frame->wWidth; > sel->r.height = stream->cur_frame->wHeight; > - mutex_unlock(&stream->mutex); > > return 0; > } > diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h > index 757254fc4fe930ae61c9d0425f04d4cd074a617e..86765b9d7935f0888476249c3fb826cd7f36b35c 100644 > --- a/drivers/media/usb/uvc/uvcvideo.h > +++ b/drivers/media/usb/uvc/uvcvideo.h > @@ -469,12 +469,6 @@ struct uvc_streaming { > const struct uvc_format *cur_format; > const struct uvc_frame *cur_frame; > > - /* > - * Protect access to ctrl, cur_format, cur_frame and hardware video > - * probe control. > - */ > - struct mutex mutex; > - Could you please instead keep this mutex and drop uvc_video_queue.mutex ? The rationale is that the same lock is now used to protect the queue operations and to serialize the ioctls. It's therefore a higher-level lock, which should be stored in the higher-level object, not in the queue. You can then also drop the lock assignment in uvc_queue.c that reads queue->queue.lock = &queue->mutex; as videobuf2 and the V4L2 core will use the video device lock when no queue lock is set. The comment at the top of uvc_queue.c may need to be updated. > /* Buffers queue. */ > unsigned int frozen : 1; > struct uvc_video_queue queue; > > --- > base-commit: d968e50b5c26642754492dea23cbd3592bde62d8 > change-id: 20250716-uvc-onelocksless-b66658e01f89 -- Regards, Laurent Pinchart