diff mbox

[v5,5/5] dma-buf/sync_file: only enable fence signalling on poll()

Message ID 1470363854-7846-5-git-send-email-gustavo@padovan.org (mailing list archive)
State New, archived
Headers show

Commit Message

Gustavo Padovan Aug. 5, 2016, 2:24 a.m. UTC 
From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>

Signalling doesn't need to be enabled at sync_file creation, it is only
required if userspace waiting the fence to signal through poll().

Thus we delay fence_add_callback() until poll is called. It only adds the
callback the first time poll() is called. This avoid re-adding the same
callback multiple times.

v2: rebase and update to work with new fence support for sync_file

v3: use atomic operation to set enabled and protect fence_add_callback()

v4: use user bit from fence flags (comment from Chris Wilson)

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
---
 drivers/dma-buf/sync_file.c | 22 +++++++++++++---------
 include/linux/sync_file.h   |  2 ++
 2 files changed, 15 insertions(+), 9 deletions(-)

Comments

Chris Wilson Aug. 5, 2016, 7:28 a.m. UTC | #1 
On Thu, Aug 04, 2016 at 11:24:14PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> 
> Signalling doesn't need to be enabled at sync_file creation, it is only
> required if userspace waiting the fence to signal through poll().
> 
> Thus we delay fence_add_callback() until poll is called. It only adds the
> callback the first time poll() is called. This avoid re-adding the same
> callback multiple times.
> 
> v2: rebase and update to work with new fence support for sync_file
> 
> v3: use atomic operation to set enabled and protect fence_add_callback()
> 
> v4: use user bit from fence flags (comment from Chris Wilson)
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> ---
> +	if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
> +		if (fence_add_callback(sync_file->fence, &sync_file->cb,
> +				   fence_check_cb_func) < 0)
> +			wake_up_all(&sync_file->wq);
> +	}
> +
>  	status = fence_is_signaled(sync_file->fence);

status can only be true/false here.
	return fence_is_signaled(sync_file->fence) ? POLLIN : 0;

Reviwed-by: Chris Wilson <chris@chris-wilson.co.uk>
-Chris
Chris Wilson Aug. 5, 2016, 7:42 a.m. UTC | #2 
On Fri, Aug 05, 2016 at 08:28:15AM +0100, Chris Wilson wrote:
> On Thu, Aug 04, 2016 at 11:24:14PM -0300, Gustavo Padovan wrote:
> > From: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> > 
> > Signalling doesn't need to be enabled at sync_file creation, it is only
> > required if userspace waiting the fence to signal through poll().
> > 
> > Thus we delay fence_add_callback() until poll is called. It only adds the
> > callback the first time poll() is called. This avoid re-adding the same
> > callback multiple times.
> > 
> > v2: rebase and update to work with new fence support for sync_file
> > 
> > v3: use atomic operation to set enabled and protect fence_add_callback()
> > 
> > v4: use user bit from fence flags (comment from Chris Wilson)
> > 
> > Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
> > ---
> > +	if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
> > +		if (fence_add_callback(sync_file->fence, &sync_file->cb,
> > +				   fence_check_cb_func) < 0)
> > +			wake_up_all(&sync_file->wq);
> > +	}
> > +
> >  	status = fence_is_signaled(sync_file->fence);
> 
> status can only be true/false here.
> 	return fence_is_signaled(sync_file->fence) ? POLLIN : 0;
> 
> Reviwed-by: Chris Wilson <chris@chris-wilson.co.uk>

Reviewed-by

/me goes back to drinking his coffee
-Chris
diff mbox

Patch

diff --git a/drivers/dma-buf/sync_file.c b/drivers/dma-buf/sync_file.c
index 2873760..ec61c50 100644
--- a/drivers/dma-buf/sync_file.c
+++ b/drivers/dma-buf/sync_file.c
@@ -86,8 +86,6 @@  struct sync_file *sync_file_create(struct fence *fence)
 		 fence->ops->get_timeline_name(fence), fence->context,
 		 fence->seqno);
 
-	fence_add_callback(fence, &sync_file->cb, fence_check_cb_func);
-
 	return sync_file;
 }
 EXPORT_SYMBOL(sync_file_create);
@@ -274,9 +272,6 @@  static struct sync_file *sync_file_merge(const char *name, struct sync_file *a,
 		goto err;
 	}
 
-	fence_add_callback(sync_file->fence, &sync_file->cb,
-			   fence_check_cb_func);
-
 	strlcpy(sync_file->name, name, sizeof(sync_file->name));
 	return sync_file;
 
@@ -291,7 +286,8 @@  static void sync_file_free(struct kref *kref)
 	struct sync_file *sync_file = container_of(kref, struct sync_file,
 						     kref);
 
-	fence_remove_callback(sync_file->fence, &sync_file->cb);
+	if (test_bit(POLL_ENABLED, &sync_file->fence->flags))
+		fence_remove_callback(sync_file->fence, &sync_file->cb);
 	fence_put(sync_file->fence);
 	kfree(sync_file);
 }
@@ -311,13 +307,21 @@  static unsigned int sync_file_poll(struct file *file, poll_table *wait)
 
 	poll_wait(file, &sync_file->wq, wait);
 
+	if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
+		if (fence_add_callback(sync_file->fence, &sync_file->cb,
+				   fence_check_cb_func) < 0)
+			wake_up_all(&sync_file->wq);
+	}
+
 	status = fence_is_signaled(sync_file->fence);
 
-	if (status)
-		return POLLIN;
+	if (!status)
+		return 0;
+
 	if (status < 0)
 		return POLLERR;
-	return 0;
+
+	return POLLIN;
 }
 
 static long sync_file_ioctl_merge(struct sync_file *sync_file,
diff --git a/include/linux/sync_file.h b/include/linux/sync_file.h
index f7de5a0..aa17ccf 100644
--- a/include/linux/sync_file.h
+++ b/include/linux/sync_file.h
@@ -45,6 +45,8 @@  struct sync_file {
 	struct fence_cb cb;
 };
 
+#define POLL_ENABLED FENCE_FLAG_USER_BITS
+
 struct sync_file *sync_file_create(struct fence *fence);
 struct fence *sync_file_get_fence(int fd);