Bug 227471 – RemotePlayback must keep its media element alive when there is a pending activity

• Status: RESOLVED
• Resolution: FIXED
• Component: Media

[Ryosuke Niwa]

When there is a pending activity in RemotePlayback (e.g. watchAvailability has been called but not yet completed)
then it must keep its media element alive by adding it as an opaque root to GC.

[Ryosuke Niwa]

<rdar://79694015>

[Ryosuke Niwa]

Created attachment 432445 [details]
Patch

[Geoffrey Garen]

Comment on attachment 432445 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=432445&action=review

> Source/WebCore/Modules/remoteplayback/RemotePlayback.idl:39
> +    GenerateIsReachable=ImplOwnerNodeRoot,
> +    GenerateAddOpaqueRoot=ownerNodeConcurrently,

At first glance, this strikes me as incorrect.

An opaque root should be the *root* of a tree of objects. For example, root(ownerNode()), which is usually the document, is an appropriate opaque root. 

In this case, even though our isReachable() function specifies root(ownerNode()), our addOpaqueRoot() function specifies just plain ownerNode(). This means that, if RemotePlaybackState is the last reference to a disconnected tree of nodes, or to a document, it will not cause the tree of nodes or document to be retained. Perhaps this is an edge case that is not super observable in practice. But I thought I'd point it out.

[Ryosuke Niwa]

(In reply to Geoffrey Garen from comment #3)
> Comment on attachment 432445 [details]
> Patch
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=432445&action=review
> 
> > Source/WebCore/Modules/remoteplayback/RemotePlayback.idl:39
> > +    GenerateIsReachable=ImplOwnerNodeRoot,
> > +    GenerateAddOpaqueRoot=ownerNodeConcurrently,
> 
> At first glance, this strikes me as incorrect.
> 
> An opaque root should be the *root* of a tree of objects. For example,
> root(ownerNode()), which is usually the document, is an appropriate opaque
> root. 
> 
> In this case, even though our isReachable() function specifies
> root(ownerNode()), our addOpaqueRoot() function specifies just plain
> ownerNode(). This means that, if RemotePlaybackState is the last reference
> to a disconnected tree of nodes, or to a document, it will not cause the
> tree of nodes or document to be retained. Perhaps this is an edge case that
> is not super observable in practice. But I thought I'd point it out.

Yikes, you're right. Fixed it and added an extra assertion for this in the test.

[Ryosuke Niwa]

Created attachment 432466 [details]
Patch

[Geoffrey Garen]

Comment on attachment 432466 [details]
Patch

EWS failure looks real.

[Ryosuke Niwa]

Created attachment 432560 [details]
Patch

[Geoffrey Garen]

Comment on attachment 432560 [details]
Patch

r=me

[Ryosuke Niwa]

Comment on attachment 432560 [details]
Patch

Clearing flags on attachment: 432560

Committed r279443 (239299@main): <https://commits.webkit.org/239299@main>

[Ryosuke Niwa]

All reviewed patches have been landed.  Closing bug.