Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750981AbeAPRXZ (ORCPT + 1 other); Tue, 16 Jan 2018 12:23:25 -0500 Received: from galahad.ideasonboard.com ([185.26.127.97]:40163 "EHLO galahad.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750747AbeAPRXY (ORCPT ); Tue, 16 Jan 2018 12:23:24 -0500 From: Laurent Pinchart To: Kieran Bingham Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Guennadi Liakhovetski , Olivier BRAUN , Troy Kisky Subject: Re: [RFT PATCH v3 4/6] uvcvideo: queue: Simplify spin-lock usage Date: Tue, 16 Jan 2018 19:23:27 +0200 Message-ID: <1566744.FFqUaHsn7F@avalon> Organization: Ideas on Board Oy In-Reply-To: <9f83cda1d54615e068c20fcadf69a1f09ae50ec1.1515748369.git-series.kieran.bingham@ideasonboard.com> References: <9f83cda1d54615e068c20fcadf69a1f09ae50ec1.1515748369.git-series.kieran.bingham@ideasonboard.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: Hi Kieran, Thank you for the patch. On Friday, 12 January 2018 11:19:26 EET Kieran Bingham wrote: > Both uvc_start_streaming(), and uvc_stop_streaming() are called from > userspace context. As such, they do not need to save the IRQ state, and > can use spin_lock_irq() and spin_unlock_irq() respectively. Note that userspace context isn't enough, the key part is that they're called with interrupts enabled. If they were called from userspace context but under a spin_lock_irq() you couldn't use spin_unlock_irq() in those functions. > Signed-off-by: Kieran Bingham > --- > drivers/media/usb/uvc/uvc_queue.c | 10 ++++------ > 1 file changed, 4 insertions(+), 6 deletions(-) > > diff --git a/drivers/media/usb/uvc/uvc_queue.c > b/drivers/media/usb/uvc/uvc_queue.c index 4a581d631525..ddac4d89a291 100644 > --- a/drivers/media/usb/uvc/uvc_queue.c > +++ b/drivers/media/usb/uvc/uvc_queue.c > @@ -158,7 +158,6 @@ static int uvc_start_streaming(struct vb2_queue *vq, > unsigned int count) { > struct uvc_video_queue *queue = vb2_get_drv_priv(vq); > struct uvc_streaming *stream = uvc_queue_to_stream(queue); > - unsigned long flags; > int ret; > > queue->buf_used = 0; > @@ -167,9 +166,9 @@ static int uvc_start_streaming(struct vb2_queue *vq, > unsigned int count) if (ret == 0) > return 0; > > - spin_lock_irqsave(&queue->irqlock, flags); > + spin_lock_irq(&queue->irqlock); > uvc_queue_return_buffers(queue, UVC_BUF_STATE_QUEUED); > - spin_unlock_irqrestore(&queue->irqlock, flags); > + spin_unlock_irq(&queue->irqlock); > > return ret; > } > @@ -178,13 +177,12 @@ static void uvc_stop_streaming(struct vb2_queue *vq) > { > struct uvc_video_queue *queue = vb2_get_drv_priv(vq); > struct uvc_streaming *stream = uvc_queue_to_stream(queue); > - unsigned long flags; > > uvc_video_enable(stream, 0); > > - spin_lock_irqsave(&queue->irqlock, flags); > + spin_lock_irq(&queue->irqlock); > uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR); > - spin_unlock_irqrestore(&queue->irqlock, flags); > + spin_unlock_irq(&queue->irqlock); > } Please add a one-line comment above both functions to state /* Must be called with interrupts enabled. */ With this and the commit message updated, Reviewed-by: Laurent Pinchart > static const struct vb2_ops uvc_queue_qops = { -- Regards, Laurent Pinchart