Re: [PATCH v2 01/10] media: v4l2-ctrls: Add missing v4l2 ctrl unlock

[Hans Verkuil]

On 04/19/18 17:41, Paul Kocialkowski wrote:
> This adds a missing v4l2_ctrl_unlock call that is required to avoid
> deadlocks.
> 
> Signed-off-by: Paul Kocialkowski 
> ---
>  drivers/media/v4l2-core/v4l2-ctrls.c | 7 ++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c 
> b/drivers/media/v4l2-core/v4l2-ctrls.c
> index f67e9f5531fa..ba05a8b9a095 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -3614,10 +3614,12 @@ void v4l2_ctrl_request_complete(struct media_request 
> *req,
>   continue;
>  
>   v4l2_ctrl_lock(ctrl);
> +
>   if (ref->req)
>   ptr_to_ptr(ctrl, ref->req->p_req, ref->p_req);
>   else
>   ptr_to_ptr(ctrl, ctrl->p_cur, ref->p_req);
> +
>   v4l2_ctrl_unlock(ctrl);
>   }
>  
> @@ -3677,8 +3679,11 @@ void v4l2_ctrl_request_setup(struct media_request *req,
>   }
>   }
>   }
> - if (!have_new_data)
> +
> + if (!have_new_data) {
> + v4l2_ctrl_unlock(master);
>   continue;
> + }

Oops! Thanks for finding this. I'll fold this into the relevant patch in my 
tree.

>  
>   for (i = 0; i < master->ncontrols; i++) {
>   if (master->cluster[i]) {
> 

Regards,

Hans

Re: [PATCH v2 01/10] media: v4l2-ctrls: Add missing v4l2 ctrl unlock

[Maxime Ripard]

On Thu, Apr 19, 2018 at 05:41:15PM +0200, Paul Kocialkowski wrote:
> This adds a missing v4l2_ctrl_unlock call that is required to avoid
> deadlocks.

Maybe you can explain what the deadlock scenario is?

> Signed-off-by: Paul Kocialkowski 
> ---
>  drivers/media/v4l2-core/v4l2-ctrls.c | 7 ++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c 
> b/drivers/media/v4l2-core/v4l2-ctrls.c
> index f67e9f5531fa..ba05a8b9a095 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -3614,10 +3614,12 @@ void v4l2_ctrl_request_complete(struct media_request 
> *req,
>   continue;
>  
>   v4l2_ctrl_lock(ctrl);
> +
>   if (ref->req)
>   ptr_to_ptr(ctrl, ref->req->p_req, ref->p_req);
>   else
>   ptr_to_ptr(ctrl, ctrl->p_cur, ref->p_req);
> +

I'm not sure that this is relevant in this patch.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com


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[PATCH v2 01/10] media: v4l2-ctrls: Add missing v4l2 ctrl unlock

[Paul Kocialkowski]

This adds a missing v4l2_ctrl_unlock call that is required to avoid
deadlocks.

Signed-off-by: Paul Kocialkowski 
---
 drivers/media/v4l2-core/v4l2-ctrls.c | 7 ++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c 
b/drivers/media/v4l2-core/v4l2-ctrls.c
index f67e9f5531fa..ba05a8b9a095 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -3614,10 +3614,12 @@ void v4l2_ctrl_request_complete(struct media_request 
*req,
continue;
 
v4l2_ctrl_lock(ctrl);
+
if (ref->req)
ptr_to_ptr(ctrl, ref->req->p_req, ref->p_req);
else
ptr_to_ptr(ctrl, ctrl->p_cur, ref->p_req);
+
v4l2_ctrl_unlock(ctrl);
}
 
@@ -3677,8 +3679,11 @@ void v4l2_ctrl_request_setup(struct media_request *req,
}
}
}
-   if (!have_new_data)
+
+   if (!have_new_data) {
+   v4l2_ctrl_unlock(master);
continue;
+   }
 
for (i = 0; i < master->ncontrols; i++) {
if (master->cluster[i]) {
-- 
2.16.3