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SubjectRe: [Intel-gfx] [PATCH] drm/i915: Fix lock dropping in intel_tv_detect()
On Mon, Sep 01, 2014 at 11:09:46AM +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> When intel_tv_detect() fails to do load detection it would forget to
> drop the locks and clean up the acquire context. Fix it up.
>
> This is a regression from:
> commit 208bf9fdcd3575aa4a5d48b3e0295f7cdaf6fc44
> Author: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Date: Mon Aug 11 13:15:35 2014 +0300
>
> drm/i915: Fix locking for intel_enable_pipe_a()
>
> Cc: Tibor Billes <tbilles@gmx.com>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_tv.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
> index 32186a6..abbf0ea 100644
> --- a/drivers/gpu/drm/i915/intel_tv.c
> +++ b/drivers/gpu/drm/i915/intel_tv.c
> @@ -1311,7 +1311,8 @@ intel_tv_detect(struct drm_connector *connector, bool force)
> {
> struct drm_display_mode mode;
> struct intel_tv *intel_tv = intel_attached_tv(connector);
> - int type;
> + enum drm_connector_status status = connector->status;
> + int type = -1;
>
> DRM_DEBUG_KMS("[CONNECTOR:%d:%s] force=%d\n",
> connector->base.id, connector->name,
> @@ -1328,21 +1329,23 @@ intel_tv_detect(struct drm_connector *connector, bool force)
> if (intel_get_load_detect_pipe(connector, &mode, &tmp, &ctx)) {
> type = intel_tv_detect_type(intel_tv, connector);
> intel_release_load_detect_pipe(connector, &tmp);
> + status = type < 0 ?
> + connector_status_disconnected :
> + connector_status_connected;
> } else
> - return connector_status_unknown;
> + status = connector_status_unknown;
>
> drm_modeset_drop_locks(&ctx);
> drm_modeset_acquire_fini(&ctx);
> - } else
> - return connector->status;
> + }
>
> if (type < 0)
> - return connector_status_disconnected;
> + return status;
>
> intel_tv->type = type;
> intel_tv_find_better_format(connector);
>
> - return connector_status_connected;
> + return status;

Hmm, this makes the code unclear. if type != -1, status should always be
connected.

I think:

if (status != connector_status_connected)
return status;

if (WARN_ON(type < 0))
return connector_status_disconnected;

intel_tv->type = type;
find_better_format();
return connector_status_connected;

And leave type unset to encourage gcc.



diff --git a/drivers/gpu/drm/i915/intel_tv.c b/drivers/gpu/drm/i915/intel_tv.c
index 32186a6..a109b7b 100644
--- a/drivers/gpu/drm/i915/intel_tv.c
+++ b/drivers/gpu/drm/i915/intel_tv.c
@@ -1311,6 +1311,7 @@ intel_tv_detect(struct drm_connector *connector, bool force)
{
struct drm_display_mode mode;
struct intel_tv *intel_tv = intel_attached_tv(connector);
+ enum drm_connector_status status = connector->status;
int type;

DRM_DEBUG_KMS("[CONNECTOR:%d:%s] force=%d\n",
@@ -1327,17 +1328,20 @@ intel_tv_detect(struct drm_connector *connector, bool force)

if (intel_get_load_detect_pipe(connector, &mode, &tmp, &ctx)) {
type = intel_tv_detect_type(intel_tv, connector);
+ status = type < 0 ?
+ connector_status_disconnected :
+ connector_status_connected;
+
intel_release_load_detect_pipe(connector, &tmp);
} else
- return connector_status_unknown;
+ status = connector_status_unknown;

drm_modeset_drop_locks(&ctx);
drm_modeset_acquire_fini(&ctx);
- } else
- return connector->status;
+ }

- if (type < 0)
- return connector_status_disconnected;
+ if (status != connector_status_connected)
+ return status;

intel_tv->type = type;
intel_tv_find_better_format(connector);
--
Chris Wilson, Intel Open Source Technology Centre
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