[PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[Bhupesh Sharma]

This patch removes the non-required spinlock acquire/release calls on
'queue_irqlock' from 'uvc_queue_next_buffer' routine.

This routine is called from 'video->encode' function (which translates to either
'uvc_video_encode_bulk' or 'uvc_video_encode_isoc') in 'uvc_video.c'.
As, the 'video->encode' routines are called with 'queue_irqlock' already held,
so acquiring a 'queue_irqlock' again in 'uvc_queue_next_buffer' routine causes
a spin lock recursion.

Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
---
 drivers/usb/gadget/uvc_queue.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/gadget/uvc_queue.c b/drivers/usb/gadget/uvc_queue.c
index d776adb..104ae9c 100644
--- a/drivers/usb/gadget/uvc_queue.c
+++ b/drivers/usb/gadget/uvc_queue.c
@@ -543,11 +543,11 @@ done:
 	return ret;
 }
 
+/* called with &queue_irqlock held.. */
 static struct uvc_buffer *
 uvc_queue_next_buffer(struct uvc_video_queue *queue, struct uvc_buffer *buf)
 {
 	struct uvc_buffer *nextbuf;
-	unsigned long flags;
 
 	if ((queue->flags & UVC_QUEUE_DROP_INCOMPLETE) &&
 	    buf->buf.length != buf->buf.bytesused) {
@@ -556,14 +556,12 @@ uvc_queue_next_buffer(struct uvc_video_queue *queue, struct uvc_buffer *buf)
 		return buf;
 	}
 
-	spin_lock_irqsave(&queue->irqlock, flags);
 	list_del(&buf->queue);
 	if (!list_empty(&queue->irqqueue))
 		nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
 					   queue);
 	else
 		nextbuf = NULL;
-	spin_unlock_irqrestore(&queue->irqlock, flags);
 
 	buf->buf.sequence = queue->sequence++;
 	do_gettimeofday(&buf->buf.timestamp);
-- 
1.7.2.2

Re: [PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[Sergei Shtylyov]

Hello.

On 22-03-2012 8:50, Bhupesh Sharma wrote:

> This patch removes the non-required spinlock acquire/release calls on
> 'queue_irqlock' from 'uvc_queue_next_buffer' routine.

    'queue->irqlock' maybe?

> This routine is called from 'video->encode' function (which translates to either
> 'uvc_video_encode_bulk' or 'uvc_video_encode_isoc') in 'uvc_video.c'.
> As, the 'video->encode' routines are called with 'queue_irqlock' already held,
> so acquiring a 'queue_irqlock' again in 'uvc_queue_next_buffer' routine causes
> a spin lock recursion.

> Signed-off-by: Bhupesh Sharma<bhupesh.sharma@st.com>
> Acked-by: Laurent Pinchart<laurent.pinchart@ideasonboard.com>
> ---
>   drivers/usb/gadget/uvc_queue.c |    4 +---
>   1 files changed, 1 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/gadget/uvc_queue.c b/drivers/usb/gadget/uvc_queue.c
> index d776adb..104ae9c 100644
> --- a/drivers/usb/gadget/uvc_queue.c
> +++ b/drivers/usb/gadget/uvc_queue.c
> @@ -543,11 +543,11 @@ done:
>   	return ret;
>   }
>
> +/* called with &queue_irqlock held.. */

    'queue->irqlock' maybe?

> @@ -556,14 +556,12 @@ uvc_queue_next_buffer(struct uvc_video_queue *queue, struct uvc_buffer *buf)
>   		return buf;
>   	}
>
> -	spin_lock_irqsave(&queue->irqlock, flags);
>   	list_del(&buf->queue);
>   	if (!list_empty(&queue->irqqueue))
>   		nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
>   					   queue);
>   	else
>   		nextbuf = NULL;
> -	spin_unlock_irqrestore(&queue->irqlock, flags);
>
>   	buf->buf.sequence = queue->sequence++;
>   	do_gettimeofday(&buf->buf.timestamp);

WBR, Sergei

Re: [PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[Greg KH]

On Thu, Mar 22, 2012 at 10:20:37AM +0530, Bhupesh Sharma wrote:
> This patch removes the non-required spinlock acquire/release calls on
> 'queue_irqlock' from 'uvc_queue_next_buffer' routine.
> 
> This routine is called from 'video->encode' function (which translates to either
> 'uvc_video_encode_bulk' or 'uvc_video_encode_isoc') in 'uvc_video.c'.
> As, the 'video->encode' routines are called with 'queue_irqlock' already held,
> so acquiring a 'queue_irqlock' again in 'uvc_queue_next_buffer' routine causes
> a spin lock recursion.
> 
> Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
> Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> ---
>  drivers/usb/gadget/uvc_queue.c |    4 +---
>  1 files changed, 1 insertions(+), 3 deletions(-)

Please use scripts/get_maintainer.pl to determine who to send this to
(hint, it's not me...)

greg k-h

RE: [PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[Bhupesh SHARMA]

Hi Felipe,

> -----Original Message-----
> From: Greg KH [mailto:gregkh@linuxfoundation.org]
> Sent: Thursday, March 22, 2012 8:11 PM
> To: Bhupesh SHARMA
> Cc: linux-usb@vger.kernel.org; laurent.pinchart@ideasonboard.com;
> spear-devel; linux-media@vger.kernel.org
> Subject: Re: [PATCH] usb: gadget/uvc: Remove non-required locking from
> 'uvc_queue_next_buffer' routine
> 
> On Thu, Mar 22, 2012 at 10:20:37AM +0530, Bhupesh Sharma wrote:
> > This patch removes the non-required spinlock acquire/release calls on
> > 'queue_irqlock' from 'uvc_queue_next_buffer' routine.
> >
> > This routine is called from 'video->encode' function (which
> translates to either
> > 'uvc_video_encode_bulk' or 'uvc_video_encode_isoc') in 'uvc_video.c'.
> > As, the 'video->encode' routines are called with 'queue_irqlock'
> already held,
> > so acquiring a 'queue_irqlock' again in 'uvc_queue_next_buffer'
> routine causes
> > a spin lock recursion.
> >
> > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
> > Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > ---
> >  drivers/usb/gadget/uvc_queue.c |    4 +---
> >  1 files changed, 1 insertions(+), 3 deletions(-)
> 
> Please use scripts/get_maintainer.pl to determine who to send this to
> (hint, it's not me...)
> 

Can you please pick this USB webcam gadget/peripheral specific patch
in your tree?

Regards,
Bhupesh

Re: [PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[Laurent Pinchart]

Hi Bhupesh,

On Friday 23 March 2012 17:31:19 Bhupesh SHARMA wrote:
> On Thursday, March 22, 2012 8:11 PM Gregg KH wrote:
> > On Thu, Mar 22, 2012 at 10:20:37AM +0530, Bhupesh Sharma wrote:
> > > This patch removes the non-required spinlock acquire/release calls on
> > > 'queue_irqlock' from 'uvc_queue_next_buffer' routine.
> > > 
> > > This routine is called from 'video->encode' function (which translates
> > > to either 'uvc_video_encode_bulk' or 'uvc_video_encode_isoc') in
> > > 'uvc_video.c'. As, the 'video->encode' routines are called with
> > > 'queue_irqlock' already held, so acquiring a 'queue_irqlock' again in
> > > 'uvc_queue_next_buffer' routine causes a spin lock recursion.
> > > 
> > > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
> > > Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > ---
> > > 
> > >  drivers/usb/gadget/uvc_queue.c |    4 +---
> > >  1 files changed, 1 insertions(+), 3 deletions(-)
> > 
> > Please use scripts/get_maintainer.pl to determine who to send this to
> > (hint, it's not me...)
> 
> Can you please pick this USB webcam gadget/peripheral specific patch
> in your tree?

Could you please first resubmit with the comments fix as asked by Sergei 
Shtylyov ? (s/queue_irqlock/queue->irqlock/)

-- 
Regards,

Laurent Pinchart

RE: [PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[Bhupesh SHARMA]

Hi Laurent,

> -----Original Message-----
> From: Laurent Pinchart [mailto:laurent.pinchart@ideasonboard.com]
> Sent: Friday, March 23, 2012 3:30 PM
> To: Bhupesh SHARMA
> Cc: balbi@ti.com; linux-usb@vger.kernel.org; spear-devel; linux-
> media@vger.kernel.org; Greg KH
> Subject: Re: [PATCH] usb: gadget/uvc: Remove non-required locking from
> 'uvc_queue_next_buffer' routine
> 
> Hi Bhupesh,
> 
> On Friday 23 March 2012 17:31:19 Bhupesh SHARMA wrote:
> > On Thursday, March 22, 2012 8:11 PM Gregg KH wrote:
> > > On Thu, Mar 22, 2012 at 10:20:37AM +0530, Bhupesh Sharma wrote:
> > > > This patch removes the non-required spinlock acquire/release
> calls on
> > > > 'queue_irqlock' from 'uvc_queue_next_buffer' routine.
> > > >
> > > > This routine is called from 'video->encode' function (which
> translates
> > > > to either 'uvc_video_encode_bulk' or 'uvc_video_encode_isoc') in
> > > > 'uvc_video.c'. As, the 'video->encode' routines are called with
> > > > 'queue_irqlock' already held, so acquiring a 'queue_irqlock'
> again in
> > > > 'uvc_queue_next_buffer' routine causes a spin lock recursion.
> > > >
> > > > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
> > > > Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > > ---
> > > >
> > > >  drivers/usb/gadget/uvc_queue.c |    4 +---
> > > >  1 files changed, 1 insertions(+), 3 deletions(-)
> > >
> > > Please use scripts/get_maintainer.pl to determine who to send this
> to
> > > (hint, it's not me...)
> >
> > Can you please pick this USB webcam gadget/peripheral specific patch
> > in your tree?
> 
> Could you please first resubmit with the comments fix as asked by
> Sergei
> Shtylyov ? (s/queue_irqlock/queue->irqlock/)
> 

Ok. I will make the changes as suggested by Sergei and then resubmit
the patch..

Regards,
Bhupesh

Re: [PATCH] usb: gadget/uvc: Remove non-required locking from 'uvc_queue_next_buffer' routine

[Greg KH]

On Fri, Mar 23, 2012 at 05:31:19PM +0800, Bhupesh SHARMA wrote:
> Hi Felipe,
> 
> > -----Original Message-----
> > From: Greg KH [mailto:gregkh@linuxfoundation.org]
> > Sent: Thursday, March 22, 2012 8:11 PM
> > To: Bhupesh SHARMA
> > Cc: linux-usb@vger.kernel.org; laurent.pinchart@ideasonboard.com;
> > spear-devel; linux-media@vger.kernel.org
> > Subject: Re: [PATCH] usb: gadget/uvc: Remove non-required locking from
> > 'uvc_queue_next_buffer' routine
> > 
> > On Thu, Mar 22, 2012 at 10:20:37AM +0530, Bhupesh Sharma wrote:
> > > This patch removes the non-required spinlock acquire/release calls on
> > > 'queue_irqlock' from 'uvc_queue_next_buffer' routine.
> > >
> > > This routine is called from 'video->encode' function (which
> > translates to either
> > > 'uvc_video_encode_bulk' or 'uvc_video_encode_isoc') in 'uvc_video.c'.
> > > As, the 'video->encode' routines are called with 'queue_irqlock'
> > already held,
> > > so acquiring a 'queue_irqlock' again in 'uvc_queue_next_buffer'
> > routine causes
> > > a spin lock recursion.
> > >
> > > Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
> > > Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > > ---
> > >  drivers/usb/gadget/uvc_queue.c |    4 +---
> > >  1 files changed, 1 insertions(+), 3 deletions(-)
> > 
> > Please use scripts/get_maintainer.pl to determine who to send this to
> > (hint, it's not me...)
> > 
> 
> Can you please pick this USB webcam gadget/peripheral specific patch
> in your tree?

You didn't put the patch in your request.  Hint, just resend it with the
proper information, digging patches out of old email threads is a major
pain when you are dealing with the patch load kernel maintainers do.

thanks,

greg k-h