[PATCH v3 0/2] drm: rework flip-work framework

[PATCH v3 0/2] drm: rework flip-work framework

[Boris BREZILLON]

Hello,

This patch series reworks the flip-work framework to make it safe when
calling drm_flip_work_queue from atomic contexts.

The 2nd patch of this series is optional, as it only reworks
drm_flip_work_init prototype to remove unneeded size argument and
return code (this function cannot fail anymore).

Best Regards,

Boris

Changes since v2:
- add missing spin_lock_init
- fix flip utils description

Changes since v1:
- add gfp flags argument to drm_flip_work_allocate_task function
- make drm_flip_work_queue safe when called from atomic context

Boris BREZILLON (2):
  drm: rework flip-work helpers to avoid calling func when the FIFO is
    full
  drm: flip-work: change drm_flip_work_init prototype

 drivers/gpu/drm/drm_flip_work.c          | 105 ++++++++++++++++++++++---------
 drivers/gpu/drm/msm/mdp/mdp4/mdp4_crtc.c |  19 ++----
 drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c |  16 +----
 drivers/gpu/drm/omapdrm/omap_plane.c     |  14 +----
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c     |   6 +-
 include/drm/drm_flip_work.h              |  33 +++++++---
 6 files changed, 108 insertions(+), 85 deletions(-)

-- 
1.8.3.2

[PATCH v3 1/2] drm: rework flip-work helpers to avoid calling func when the FIFO is full

[Boris BREZILLON]

Make use of lists instead of kfifo in order to dynamically allocate
task entry when someone require some delayed work, and thus preventing
drm_flip_work_queue from directly calling func instead of queuing this
call.
This allow drm_flip_work_queue to be safely called even within irq
handlers.

Add new helper functions to allocate a flip work task and queue it when
needed. This prevents allocating data within irq context (which might
impact the time spent in the irq handler).

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
---
 drivers/gpu/drm/drm_flip_work.c | 97 +++++++++++++++++++++++++++++++----------
 include/drm/drm_flip_work.h     | 31 +++++++++----
 2 files changed, 96 insertions(+), 32 deletions(-)

diff --git a/drivers/gpu/drm/drm_flip_work.c b/drivers/gpu/drm/drm_flip_work.c
index f9c7fa3..6f4ae5b 100644
--- a/drivers/gpu/drm/drm_flip_work.c
+++ b/drivers/gpu/drm/drm_flip_work.c
@@ -25,6 +25,44 @@
 #include "drm_flip_work.h"
 
 /**
+ * drm_flip_work_allocate_task - allocate a flip-work task
+ * @data: data associated to the task
+ * @flags: allocator flags
+ *
+ * Allocate a drm_flip_task object and attach private data to it.
+ */
+struct drm_flip_task *drm_flip_work_allocate_task(void *data, gfp_t flags)
+{
+	struct drm_flip_task *task;
+
+	task = kzalloc(sizeof(*task), flags);
+	if (task)
+		task->data = data;
+
+	return task;
+}
+EXPORT_SYMBOL(drm_flip_work_allocate_task);
+
+/**
+ * drm_flip_work_queue_task - queue a specific task
+ * @work: the flip-work
+ * @task: the task to handle
+ *
+ * Queues task, that will later be run (passed back to drm_flip_func_t
+ * func) on a work queue after drm_flip_work_commit() is called.
+ */
+void drm_flip_work_queue_task(struct drm_flip_work *work,
+			      struct drm_flip_task *task)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&work->lock, flags);
+	list_add_tail(&task->node, &work->queued);
+	spin_unlock_irqrestore(&work->lock, flags);
+}
+EXPORT_SYMBOL(drm_flip_work_queue_task);
+
+/**
  * drm_flip_work_queue - queue work
  * @work: the flip-work
  * @val: the value to queue
@@ -34,10 +72,14 @@
  */
 void drm_flip_work_queue(struct drm_flip_work *work, void *val)
 {
-	if (kfifo_put(&work->fifo, val)) {
-		atomic_inc(&work->pending);
+	struct drm_flip_task *task;
+
+	task = drm_flip_work_allocate_task(val,
+				drm_can_sleep() ? GFP_KERNEL : GFP_ATOMIC);
+	if (task) {
+		drm_flip_work_queue_task(work, task);
 	} else {
-		DRM_ERROR("%s fifo full!\n", work->name);
+		DRM_ERROR("%s could not allocate task!\n", work->name);
 		work->func(work, val);
 	}
 }
@@ -56,9 +98,12 @@ EXPORT_SYMBOL(drm_flip_work_queue);
 void drm_flip_work_commit(struct drm_flip_work *work,
 		struct workqueue_struct *wq)
 {
-	uint32_t pending = atomic_read(&work->pending);
-	atomic_add(pending, &work->count);
-	atomic_sub(pending, &work->pending);
+	unsigned long flags;
+
+	spin_lock_irqsave(&work->lock, flags);
+	list_splice_tail(&work->queued, &work->commited);
+	INIT_LIST_HEAD(&work->queued);
+	spin_unlock_irqrestore(&work->lock, flags);
 	queue_work(wq, &work->worker);
 }
 EXPORT_SYMBOL(drm_flip_work_commit);
@@ -66,14 +111,26 @@ EXPORT_SYMBOL(drm_flip_work_commit);
 static void flip_worker(struct work_struct *w)
 {
 	struct drm_flip_work *work = container_of(w, struct drm_flip_work, worker);
-	uint32_t count = atomic_read(&work->count);
-	void *val = NULL;
+	struct list_head tasks;
+	unsigned long flags;
 
-	atomic_sub(count, &work->count);
+	while (1) {
+		struct drm_flip_task *task, *tmp;
 
-	while(count--)
-		if (!WARN_ON(!kfifo_get(&work->fifo, &val)))
-			work->func(work, val);
+		INIT_LIST_HEAD(&tasks);
+		spin_lock_irqsave(&work->lock, flags);
+		list_splice_tail(&work->commited, &tasks);
+		INIT_LIST_HEAD(&work->commited);
+		spin_unlock_irqrestore(&work->lock, flags);
+
+		if (list_empty(&tasks))
+			break;
+
+		list_for_each_entry_safe(task, tmp, &tasks, node) {
+			work->func(work, task->data);
+			kfree(task);
+		}
+	}
 }
 
 /**
@@ -91,19 +148,12 @@ static void flip_worker(struct work_struct *w)
 int drm_flip_work_init(struct drm_flip_work *work, int size,
 		const char *name, drm_flip_func_t func)
 {
-	int ret;
-
 	work->name = name;
-	atomic_set(&work->count, 0);
-	atomic_set(&work->pending, 0);
+	INIT_LIST_HEAD(&work->queued);
+	INIT_LIST_HEAD(&work->commited);
+	spin_lock_init(&work->lock);
 	work->func = func;
 
-	ret = kfifo_alloc(&work->fifo, size, GFP_KERNEL);
-	if (ret) {
-		DRM_ERROR("could not allocate %s fifo\n", name);
-		return ret;
-	}
-
 	INIT_WORK(&work->worker, flip_worker);
 
 	return 0;
@@ -118,7 +168,6 @@ EXPORT_SYMBOL(drm_flip_work_init);
  */
 void drm_flip_work_cleanup(struct drm_flip_work *work)
 {
-	WARN_ON(!kfifo_is_empty(&work->fifo));
-	kfifo_free(&work->fifo);
+	WARN_ON(!list_empty(&work->queued) || !list_empty(&work->commited));
 }
 EXPORT_SYMBOL(drm_flip_work_cleanup);
diff --git a/include/drm/drm_flip_work.h b/include/drm/drm_flip_work.h
index 9eed34d..3fcb4c4 100644
--- a/include/drm/drm_flip_work.h
+++ b/include/drm/drm_flip_work.h
@@ -25,6 +25,7 @@
 #define DRM_FLIP_WORK_H
 
 #include <linux/kfifo.h>
+#include <linux/spinlock.h>
 #include <linux/workqueue.h>
 
 /**
@@ -32,9 +33,9 @@
  *
  * Util to queue up work to run from work-queue context after flip/vblank.
  * Typically this can be used to defer unref of framebuffer's, cursor
- * bo's, etc until after vblank.  The APIs are all safe (and lockless)
- * for up to one producer and once consumer at a time.  The single-consumer
- * aspect is ensured by committing the queued work to a single work-queue.
+ * bo's, etc until after vblank.  The APIs are all thread-safe.
+ * Moreover, drm_flip_work_queue_task and drm_flip_work_queue can be called
+ * in atomic context.
  */
 
 struct drm_flip_work;
@@ -51,22 +52,36 @@ struct drm_flip_work;
 typedef void (*drm_flip_func_t)(struct drm_flip_work *work, void *val);
 
 /**
+ * struct drm_flip_task - flip work task
+ * @node: list entry element
+ * @data: data to pass to work->func
+ */
+struct drm_flip_task {
+	struct list_head node;
+	void *data;
+};
+
+/**
  * struct drm_flip_work - flip work queue
  * @name: debug name
- * @pending: number of queued but not committed items
- * @count: number of committed items
  * @func: callback fxn called for each committed item
  * @worker: worker which calls @func
- * @fifo: queue of committed items
+ * @queued: queued tasks
+ * @commited: commited tasks
+ * @lock: lock to access queued and commited lists
  */
 struct drm_flip_work {
 	const char *name;
-	atomic_t pending, count;
 	drm_flip_func_t func;
 	struct work_struct worker;
-	DECLARE_KFIFO_PTR(fifo, void *);
+	struct list_head queued;
+	struct list_head commited;
+	spinlock_t lock;
 };
 
+struct drm_flip_task *drm_flip_work_allocate_task(void *data, gfp_t flags);
+void drm_flip_work_queue_task(struct drm_flip_work *work,
+			      struct drm_flip_task *task);
 void drm_flip_work_queue(struct drm_flip_work *work, void *val);
 void drm_flip_work_commit(struct drm_flip_work *work,
 		struct workqueue_struct *wq);
-- 
1.8.3.2

[PATCH v3 2/2] drm: flip-work: change drm_flip_work_init prototype

[Boris BREZILLON]

Now that we're using lists instead of kfifo to store drm flip-work tasks
we do not need the size parameter passed to drm_flip_work_init function
anymore.
Moreover this function cannot fail anymore, we can thus remove the return
code.

Modify drm_flip_work_init users to take account of these changes.

Signed-off-by: Boris BREZILLON <boris.brezillon@free-electrons.com>
Reviewed-by: Rob Clark <robdclark@gmail.com>
---
 drivers/gpu/drm/drm_flip_work.c          |  8 +-------
 drivers/gpu/drm/msm/mdp/mdp4/mdp4_crtc.c | 19 ++++---------------
 drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c | 16 +++-------------
 drivers/gpu/drm/omapdrm/omap_plane.c     | 14 ++------------
 drivers/gpu/drm/tilcdc/tilcdc_crtc.c     |  6 +-----
 include/drm/drm_flip_work.h              |  2 +-
 6 files changed, 12 insertions(+), 53 deletions(-)

diff --git a/drivers/gpu/drm/drm_flip_work.c b/drivers/gpu/drm/drm_flip_work.c
index 6f4ae5b..43d9b95 100644
--- a/drivers/gpu/drm/drm_flip_work.c
+++ b/drivers/gpu/drm/drm_flip_work.c
@@ -136,16 +136,12 @@ static void flip_worker(struct work_struct *w)
 /**
  * drm_flip_work_init - initialize flip-work
  * @work: the flip-work to initialize
- * @size: the max queue depth
  * @name: debug name
  * @func: the callback work function
  *
  * Initializes/allocates resources for the flip-work
- *
- * RETURNS:
- * Zero on success, error code on failure.
  */
-int drm_flip_work_init(struct drm_flip_work *work, int size,
+void drm_flip_work_init(struct drm_flip_work *work,
 		const char *name, drm_flip_func_t func)
 {
 	work->name = name;
@@ -155,8 +151,6 @@ int drm_flip_work_init(struct drm_flip_work *work, int size,
 	work->func = func;
 
 	INIT_WORK(&work->worker, flip_worker);
-
-	return 0;
 }
 EXPORT_SYMBOL(drm_flip_work_init);
 
diff --git a/drivers/gpu/drm/msm/mdp/mdp4/mdp4_crtc.c b/drivers/gpu/drm/msm/mdp/mdp4/mdp4_crtc.c
index 74cebb5..44d4f93 100644
--- a/drivers/gpu/drm/msm/mdp/mdp4/mdp4_crtc.c
+++ b/drivers/gpu/drm/msm/mdp/mdp4/mdp4_crtc.c
@@ -755,10 +755,8 @@ struct drm_crtc *mdp4_crtc_init(struct drm_device *dev,
 	int ret;
 
 	mdp4_crtc = kzalloc(sizeof(*mdp4_crtc), GFP_KERNEL);
-	if (!mdp4_crtc) {
-		ret = -ENOMEM;
-		goto fail;
-	}
+	if (!mdp4_crtc)
+		return ERR_PTR(-ENOMEM);
 
 	crtc = &mdp4_crtc->base;
 
@@ -779,12 +777,9 @@ struct drm_crtc *mdp4_crtc_init(struct drm_device *dev,
 
 	spin_lock_init(&mdp4_crtc->cursor.lock);
 
-	ret = drm_flip_work_init(&mdp4_crtc->unref_fb_work, 16,
+	drm_flip_work_init(&mdp4_crtc->unref_fb_work,
 			"unref fb", unref_fb_worker);
-	if (ret)
-		goto fail;
-
-	ret = drm_flip_work_init(&mdp4_crtc->unref_cursor_work, 64,
+	drm_flip_work_init(&mdp4_crtc->unref_cursor_work,
 			"unref cursor", unref_cursor_worker);
 
 	INIT_FENCE_CB(&mdp4_crtc->pageflip_cb, pageflip_cb);
@@ -795,10 +790,4 @@ struct drm_crtc *mdp4_crtc_init(struct drm_device *dev,
 	mdp4_plane_install_properties(mdp4_crtc->plane, &crtc->base);
 
 	return crtc;
-
-fail:
-	if (crtc)
-		mdp4_crtc_destroy(crtc);
-
-	return ERR_PTR(ret);
 }
diff --git a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
index ebe2e60..a0cb374 100644
--- a/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
+++ b/drivers/gpu/drm/msm/mdp/mdp5/mdp5_crtc.c
@@ -537,10 +537,8 @@ struct drm_crtc *mdp5_crtc_init(struct drm_device *dev,
 	int ret;
 
 	mdp5_crtc = kzalloc(sizeof(*mdp5_crtc), GFP_KERNEL);
-	if (!mdp5_crtc) {
-		ret = -ENOMEM;
-		goto fail;
-	}
+	if (!mdp5_crtc)
+		return ERR_PTR(-ENOMEM);
 
 	crtc = &mdp5_crtc->base;
 
@@ -553,10 +551,8 @@ struct drm_crtc *mdp5_crtc_init(struct drm_device *dev,
 	snprintf(mdp5_crtc->name, sizeof(mdp5_crtc->name), "%s:%d",
 			pipe2name(mdp5_plane_pipe(plane)), id);
 
-	ret = drm_flip_work_init(&mdp5_crtc->unref_fb_work, 16,
+	drm_flip_work_init(&mdp5_crtc->unref_fb_work,
 			"unref fb", unref_fb_worker);
-	if (ret)
-		goto fail;
 
 	INIT_FENCE_CB(&mdp5_crtc->pageflip_cb, pageflip_cb);
 
@@ -566,10 +562,4 @@ struct drm_crtc *mdp5_crtc_init(struct drm_device *dev,
 	mdp5_plane_install_properties(mdp5_crtc->plane, &crtc->base);
 
 	return crtc;
-
-fail:
-	if (crtc)
-		mdp5_crtc_destroy(crtc);
-
-	return ERR_PTR(ret);
 }
diff --git a/drivers/gpu/drm/omapdrm/omap_plane.c b/drivers/gpu/drm/omapdrm/omap_plane.c
index 3cf31ee..847d1ca 100644
--- a/drivers/gpu/drm/omapdrm/omap_plane.c
+++ b/drivers/gpu/drm/omapdrm/omap_plane.c
@@ -397,14 +397,10 @@ struct drm_plane *omap_plane_init(struct drm_device *dev,
 
 	omap_plane = kzalloc(sizeof(*omap_plane), GFP_KERNEL);
 	if (!omap_plane)
-		goto fail;
+		return NULL;
 
-	ret = drm_flip_work_init(&omap_plane->unpin_work, 16,
+	drm_flip_work_init(&omap_plane->unpin_work,
 			"unpin", unpin_worker);
-	if (ret) {
-		dev_err(dev->dev, "could not allocate unpin FIFO\n");
-		goto fail;
-	}
 
 	omap_plane->nformats = omap_framebuffer_get_formats(
 			omap_plane->formats, ARRAY_SIZE(omap_plane->formats),
@@ -446,10 +442,4 @@ struct drm_plane *omap_plane_init(struct drm_device *dev,
 		omap_plane->info.zorder = id;
 
 	return plane;
-
-fail:
-	if (plane)
-		omap_plane_destroy(plane);
-
-	return NULL;
 }
diff --git a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
index d642d4a0..7d782ce 100644
--- a/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
+++ b/drivers/gpu/drm/tilcdc/tilcdc_crtc.c
@@ -664,12 +664,8 @@ struct drm_crtc *tilcdc_crtc_create(struct drm_device *dev)
 	tilcdc_crtc->dpms = DRM_MODE_DPMS_OFF;
 	init_waitqueue_head(&tilcdc_crtc->frame_done_wq);
 
-	ret = drm_flip_work_init(&tilcdc_crtc->unref_work, 16,
+	drm_flip_work_init(&tilcdc_crtc->unref_work,
 			"unref", unref_worker);
-	if (ret) {
-		dev_err(dev->dev, "could not allocate unref FIFO\n");
-		goto fail;
-	}
 
 	ret = drm_crtc_init(dev, crtc, &tilcdc_crtc_funcs);
 	if (ret < 0)
diff --git a/include/drm/drm_flip_work.h b/include/drm/drm_flip_work.h
index 3fcb4c4..d387cf0 100644
--- a/include/drm/drm_flip_work.h
+++ b/include/drm/drm_flip_work.h
@@ -85,7 +85,7 @@ void drm_flip_work_queue_task(struct drm_flip_work *work,
 void drm_flip_work_queue(struct drm_flip_work *work, void *val);
 void drm_flip_work_commit(struct drm_flip_work *work,
 		struct workqueue_struct *wq);
-int drm_flip_work_init(struct drm_flip_work *work, int size,
+void drm_flip_work_init(struct drm_flip_work *work,
 		const char *name, drm_flip_func_t func);
 void drm_flip_work_cleanup(struct drm_flip_work *work);
 
-- 
1.8.3.2

Re: [PATCH v3 0/2] drm: rework flip-work framework

[Boris BREZILLON]

Hi,

On Sat, 12 Jul 2014 16:06:06 +0200
Boris BREZILLON <boris.brezillon@free-electrons.com> wrote:

> Hello,
> 
> This patch series reworks the flip-work framework to make it safe when
> calling drm_flip_work_queue from atomic contexts.
> 
> The 2nd patch of this series is optional, as it only reworks
> drm_flip_work_init prototype to remove unneeded size argument and
> return code (this function cannot fail anymore).


Atmel HLCDC driver now depends on this series and I'd like to get as
much thing as possible for HLCDC support in 3.18 (if the driver can't
make it for 3.18, at least the dependencies could).

David, Rob (and other DRM/KMS developers) do you have any concern you
would like addressed in this patch series ?

Best Regards,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v3 0/2] drm: rework flip-work framework

[Rob Clark]

On Tue, Aug 12, 2014 at 7:14 AM, Boris BREZILLON
<boris.brezillon@free-electrons.com> wrote:
> Hi,
>
> On Sat, 12 Jul 2014 16:06:06 +0200
> Boris BREZILLON <boris.brezillon@free-electrons.com> wrote:
>
>> Hello,
>>
>> This patch series reworks the flip-work framework to make it safe when
>> calling drm_flip_work_queue from atomic contexts.
>>
>> The 2nd patch of this series is optional, as it only reworks
>> drm_flip_work_init prototype to remove unneeded size argument and
>> return code (this function cannot fail anymore).
>
>
> Atmel HLCDC driver now depends on this series and I'd like to get as
> much thing as possible for HLCDC support in 3.18 (if the driver can't
> make it for 3.18, at least the dependencies could).
>
> David, Rob (and other DRM/KMS developers) do you have any concern you
> would like addressed in this patch series ?

it already has my r-b :-)

BR,
-R

> Best Regards,
>
> Boris
>
>
> --
> Boris Brezillon, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com

Re: [PATCH v3 0/2] drm: rework flip-work framework

[Boris BREZILLON]

Hi Rob,

On Tue, 12 Aug 2014 07:20:09 -0400
Rob Clark <robdclark@gmail.com> wrote:

> On Tue, Aug 12, 2014 at 7:14 AM, Boris BREZILLON
> <boris.brezillon@free-electrons.com> wrote:
> > Hi,
> >
> > On Sat, 12 Jul 2014 16:06:06 +0200
> > Boris BREZILLON <boris.brezillon@free-electrons.com> wrote:
> >
> >> Hello,
> >>
> >> This patch series reworks the flip-work framework to make it safe when
> >> calling drm_flip_work_queue from atomic contexts.
> >>
> >> The 2nd patch of this series is optional, as it only reworks
> >> drm_flip_work_init prototype to remove unneeded size argument and
> >> return code (this function cannot fail anymore).
> >
> >
> > Atmel HLCDC driver now depends on this series and I'd like to get as
> > much thing as possible for HLCDC support in 3.18 (if the driver can't
> > make it for 3.18, at least the dependencies could).
> >
> > David, Rob (and other DRM/KMS developers) do you have any concern you
> > would like addressed in this patch series ?
> 
> it already has my r-b :-)

Yes, I know, I was just checking that you were still okay with this
series ;-).

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com