Re: [PATCH v2 06/22] media: Media Controller non-locking __media_entity_pipeline_start/stop()
From: Mauro Carvalho Chehab <hidden>
Date: 2016-02-04 09:18:28
Also in:
alsa-devel, linux-media, lkml
Em Wed, 03 Feb 2016 21:03:38 -0700 Shuah Khan [off-list ref] escreveu:
Add non-locking __media_entity_pipeline_start/stop() interfaces to be called from code paths that hold the graph_mutex. For this change, the media_entity_pipeline_start() routine is renamed to __media_entity_pipeline_start() minus the graph_mutex lock and unlock. media_entity_pipeline_start() now calls the non-locking __media_entity_pipeline_start() holding the graph_lock. The stop interface, media_entity_pipeline_stop() routine is renamed to __media_entity_pipeline_stop() minus the graph_mutex lock and unlock. media_entity_pipeline_stop() now calls the non-locking __media_entity_pipeline_stop() holding the graph_lock.
Please write a better patch descriptions. The above could easily
be split into 3 or 4 paragraphs, with would make it easier to
read.
Also, too much details, written on a spaghetti style;)
It is obvious by anyone that looked at the patch that
"media_entity_pipeline_start() routine is renamed to
__media_entity_pipeline_start() minus the graph_mutex lock and
unlock."
I read exactly the same thing at the C code, *and* at the
subject of the e-mail. Patch subject/description should tell
what, why and how (but you should not repeat what can easily
be inferred from looking at the diff).
I would describe it as:
Currently, media pipeline graph traversal routines take
the graph_mutex lock.
While this works for the current code, we'll need
unlocked versions of them because
(some explanation *why* you need it, with is the main
thing that should be at the description).
So, add non-locking media_entity_pipeline_start/stop()
variations.
quoted hunk ↗ jump to hunk
Signed-off-by: Shuah Khan <redacted> --- drivers/media/media-entity.c | 34 ++++++++++++++++++++++++---------- include/media/media-entity.h | 12 ++++++++++++ 2 files changed, 36 insertions(+), 10 deletions(-)diff --git a/drivers/media/media-entity.c b/drivers/media/media-entity.c index 9b4d712..b78e4c2 100644 --- a/drivers/media/media-entity.c +++ b/drivers/media/media-entity.c@@ -365,8 +365,8 @@ EXPORT_SYMBOL_GPL(media_entity_graph_walk_next); * Pipeline management */ -__must_check int media_entity_pipeline_start(struct media_entity *entity, - struct media_pipeline *pipe) +__must_check int __media_entity_pipeline_start(struct media_entity *entity, + struct media_pipeline *pipe) { struct media_device *mdev = entity->graph_obj.mdev; struct media_entity_graph *graph = &pipe->graph;@@ -374,8 +374,6 @@ __must_check int media_entity_pipeline_start(struct media_entity *entity, struct media_link *link; int ret; - mutex_lock(&mdev->graph_mutex); - if (!pipe->streaming_count++) { ret = media_entity_graph_walk_init(&pipe->graph, mdev); if (ret)@@ -456,8 +454,6 @@ __must_check int media_entity_pipeline_start(struct media_entity *entity, } } - mutex_unlock(&mdev->graph_mutex); - return 0; error:@@ -487,19 +483,28 @@ error_graph_walk_start: if (!--pipe->streaming_count) media_entity_graph_walk_cleanup(graph); - mutex_unlock(&mdev->graph_mutex); + return ret; +} +EXPORT_SYMBOL_GPL(__media_entity_pipeline_start); +__must_check int media_entity_pipeline_start(struct media_entity *entity, + struct media_pipeline *pipe) +{ + struct media_device *mdev = entity->graph_obj.mdev; + int ret; + + mutex_lock(&mdev->graph_mutex); + ret = __media_entity_pipeline_start(entity, pipe); + mutex_unlock(&mdev->graph_mutex); return ret; } EXPORT_SYMBOL_GPL(media_entity_pipeline_start); -void media_entity_pipeline_stop(struct media_entity *entity) +void __media_entity_pipeline_stop(struct media_entity *entity) { - struct media_device *mdev = entity->graph_obj.mdev; struct media_entity_graph *graph = &entity->pipe->graph; struct media_pipeline *pipe = entity->pipe; - mutex_lock(&mdev->graph_mutex); WARN_ON(!pipe->streaming_count); media_entity_graph_walk_start(graph, entity);@@ -516,6 +521,15 @@ void media_entity_pipeline_stop(struct media_entity *entity) if (!--pipe->streaming_count) media_entity_graph_walk_cleanup(graph); +} +EXPORT_SYMBOL_GPL(__media_entity_pipeline_stop); + +void media_entity_pipeline_stop(struct media_entity *entity) +{ + struct media_device *mdev = entity->graph_obj.mdev; + + mutex_lock(&mdev->graph_mutex); + __media_entity_pipeline_stop(entity); mutex_unlock(&mdev->graph_mutex); } EXPORT_SYMBOL_GPL(media_entity_pipeline_stop);diff --git a/include/media/media-entity.h b/include/media/media-entity.h index fe485d3..c7583db 100644 --- a/include/media/media-entity.h +++ b/include/media/media-entity.h@@ -832,6 +832,12 @@ media_entity_graph_walk_next(struct media_entity_graph *graph); */ __must_check int media_entity_pipeline_start(struct media_entity *entity, struct media_pipeline *pipe); +/** + * non-locking __media_entity_pipeline_start() can be called from + * code paths that hold the graph_mutex + */ +__must_check int __media_entity_pipeline_start(struct media_entity *entity, + struct media_pipeline *pipe); /** * media_entity_pipeline_stop - Mark a pipeline as not streaming@@ -848,6 +854,12 @@ __must_check int media_entity_pipeline_start(struct media_entity *entity, void media_entity_pipeline_stop(struct media_entity *entity); /** + * non-locking __media_entity_pipeline_stop() can be called from + * code paths that hold the graph_mutex + */ +void __media_entity_pipeline_stop(struct media_entity *entity); + +/** * media_devnode_create() - creates and initializes a device node interface * * @mdev: pointer to struct &media_device