[PATCH] drm/dp/mst: make sure mst_primary mstb is valid in work function

[Dave Airlie]

From: Daniel Vetter 

This validates the mst_primary under the lock, and then calls
into the check and send function. This makes the code a lot
easier to understand the locking rules in.

Signed-off-by: Dave Airlie 
---
 drivers/gpu/drm/drm_dp_mst_topology.c | 24 +++-
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
b/drivers/gpu/drm/drm_dp_mst_topology.c
index a9c437e..8a3bfcd 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -1204,7 +1204,7 @@ static void drm_dp_check_and_send_link_address(struct 
drm_dp_mst_topology_mgr *m
   struct drm_dp_mst_branch *mstb)
 {
struct drm_dp_mst_port *port;
-
+   struct drm_dp_mst_branch *mstb_child;
if (!mstb->link_address_sent) {
drm_dp_send_link_address(mgr, mstb);
mstb->link_address_sent = true;
@@ -1219,17 +1219,31 @@ static void drm_dp_check_and_send_link_address(struct 
drm_dp_mst_topology_mgr *m
if (!port->available_pbn)
drm_dp_send_enum_path_resources(mgr, mstb, port);

-   if (port->mstb)
-   drm_dp_check_and_send_link_address(mgr, port->mstb);
+   if (port->mstb) {
+   mstb_child = drm_dp_get_validated_mstb_ref(mgr, 
port->mstb);
+   if (mstb_child) {
+   drm_dp_check_and_send_link_address(mgr, 
mstb_child);
+   drm_dp_put_mst_branch_device(mstb_child);
+   }
+   }
}
 }

 static void drm_dp_mst_link_probe_work(struct work_struct *work)
 {
struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct 
drm_dp_mst_topology_mgr, work);
+   struct drm_dp_mst_branch *mstb;

-   drm_dp_check_and_send_link_address(mgr, mgr->mst_primary);
-
+   mutex_lock(>lock);
+   mstb = mgr->mst_primary;
+   if (mstb) {
+   kref_get(>kref);
+   }
+   mutex_unlock(>lock);
+   if (mstb) {
+   drm_dp_check_and_send_link_address(mgr, mstb);
+   drm_dp_put_mst_branch_device(mstb);
+   }
 }

 static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
-- 
2.4.1

[PATCH] drm/dp/mst: make sure mst_primary mstb is valid in work function

[Daniel Vetter]

On Mon, Jun 22, 2015 at 05:31:59PM +1000, Dave Airlie wrote:
> From: Daniel Vetter 
> 
> This validates the mst_primary under the lock, and then calls
> into the check and send function. This makes the code a lot
> easier to understand the locking rules in.
> 
> Signed-off-by: Dave Airlie 

Signed-off-by: Daniel Vetter 
Reviewed-by: Daniel Vetter 

Pick what you like ;-)

> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 24 +++-
>  1 file changed, 19 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c 
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index a9c437e..8a3bfcd 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -1204,7 +1204,7 @@ static void drm_dp_check_and_send_link_address(struct 
> drm_dp_mst_topology_mgr *m
>  struct drm_dp_mst_branch *mstb)
>  {
>   struct drm_dp_mst_port *port;
> -
> + struct drm_dp_mst_branch *mstb_child;
>   if (!mstb->link_address_sent) {
>   drm_dp_send_link_address(mgr, mstb);
>   mstb->link_address_sent = true;
> @@ -1219,17 +1219,31 @@ static void drm_dp_check_and_send_link_address(struct 
> drm_dp_mst_topology_mgr *m
>   if (!port->available_pbn)
>   drm_dp_send_enum_path_resources(mgr, mstb, port);
>  
> - if (port->mstb)
> - drm_dp_check_and_send_link_address(mgr, port->mstb);
> + if (port->mstb) {
> + mstb_child = drm_dp_get_validated_mstb_ref(mgr, 
> port->mstb);
> + if (mstb_child) {
> + drm_dp_check_and_send_link_address(mgr, 
> mstb_child);
> + drm_dp_put_mst_branch_device(mstb_child);
> + }
> + }
>   }
>  }
>  
>  static void drm_dp_mst_link_probe_work(struct work_struct *work)
>  {
>   struct drm_dp_mst_topology_mgr *mgr = container_of(work, struct 
> drm_dp_mst_topology_mgr, work);
> + struct drm_dp_mst_branch *mstb;
>  
> - drm_dp_check_and_send_link_address(mgr, mgr->mst_primary);
> -
> + mutex_lock(>lock);
> + mstb = mgr->mst_primary;
> + if (mstb) {
> + kref_get(>kref);
> + }
> + mutex_unlock(>lock);
> + if (mstb) {
> + drm_dp_check_and_send_link_address(mgr, mstb);
> + drm_dp_put_mst_branch_device(mstb);
> + }
>  }
>  
>  static bool drm_dp_validate_guid(struct drm_dp_mst_topology_mgr *mgr,
> -- 
> 2.4.1
> 
> ___
> dri-devel mailing list
> dri-devel at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch