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spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388231AbeKGAge (ORCPT ); Tue, 6 Nov 2018 19:36:34 -0500 Received: from perceval.ideasonboard.com ([213.167.242.64]:51326 "EHLO perceval.ideasonboard.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387848AbeKGAge (ORCPT ); Tue, 6 Nov 2018 19:36:34 -0500 Received: from [192.168.0.21] (cpc89242-aztw30-2-0-cust488.18-1.cable.virginm.net [86.31.129.233]) by perceval.ideasonboard.com (Postfix) with ESMTPSA id 74873526; Tue, 6 Nov 2018 16:10:52 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com; s=mail; t=1541517052; bh=R/vPkzIoTDmWy/ODnbq3dMPxvSLth7xif2uc4Wyceqo=; h=Reply-To:Subject:To:Cc:References:From:Date:In-Reply-To:From; b=KVOZlOEF+pXVTFAk9tsN3AuBYy87Mln78pcJbuOC/hBmPAChFeufgGhryhAZHj4jf UZFonR0xwWo/+rAhvjmf6dcOojQCEFma5VCKLt1mIawm4vbBPIs0aws1udJyQG7Gaj vZf9W9fbpqr0GIP3z9+lBHGXQ9pICM/fQ02KqfpY= Reply-To: kieran.bingham@ideasonboard.com Subject: Re: [PATCH v4 4/6] media: uvcvideo: queue: Simplify spin-lock usage To: Laurent Pinchart Cc: linux-media@vger.kernel.org, Guennadi Liakhovetski , Olivier BRAUN , Troy Kisky , Randy Dunlap , Philipp Zabel , Mauro Carvalho Chehab , open list References: <18698388.LcrgILxgHI@avalon> From: Kieran Bingham Openpgp: preference=signencrypt Autocrypt: addr=kieran.bingham@ideasonboard.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 In-Reply-To: <18698388.LcrgILxgHI@avalon> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Laurent, On 30/07/2018 20:57, Laurent Pinchart wrote: > Hi Kieran, > > Thank you for the patch. > > On Tuesday, 27 March 2018 19:46:01 EEST Kieran Bingham wrote: >> Both uvc_start_streaming(), and uvc_stop_streaming() are called from >> userspace context, with interrupts enabled. As such, they do not need to >> save the IRQ state, and can use spin_lock_irq() and spin_unlock_irq() >> respectively. >> >> Signed-off-by: Kieran Bingham >> >> --- >> >> v4: >> - Rebase to v4.16 (linux-media/master) >> >> 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 adcc4928fae4..698d9a5a5aae 100644 >> --- a/drivers/media/usb/uvc/uvc_queue.c >> +++ b/drivers/media/usb/uvc/uvc_queue.c >> @@ -169,7 +169,6 @@ 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; >> @@ -178,9 +177,9 @@ 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; >> } >> @@ -188,14 +187,13 @@ static int uvc_start_streaming(struct vb2_queue *vq, >> unsigned int count) static void uvc_stop_streaming(struct vb2_queue *vq) >> { >> struct uvc_video_queue *queue = vb2_get_drv_priv(vq); >> - unsigned long flags; >> >> if (vq->type != V4L2_BUF_TYPE_META_CAPTURE) >> uvc_video_enable(uvc_queue_to_stream(queue), 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); >> } > > I think you missed my comment that stated > >> Please add a one-line comment above both functions to state >> >> /* Must be called with interrupts enabled. */ > > Philipp Zabel commented that you could also add lockdep_assert_irqs_enabled(), > and I think that's a good idea. I'll let you decide whether to do both, or > only add lockdep_assert_irqs_enabled(), I'm fine with either option. > > With this fixed, I think code should talk louder than comments (especially as it provides runtime verification and assertions when lockdep is enabled) - so I've gone for Philipp's suggestion here. > > Reviewed-by: Laurent Pinchart > Collected, thanks. >> static const struct vb2_ops uvc_queue_qops = { > -- Regards -- Kieran