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Auto merge of #18514 - asajeffrey:layout-dont-panic-if-no-iframe-bc, r=emilio
Remove sources of panic when laying out an iframe without a nested browsing context <!-- Please describe your changes on the following line: --> At the moment, layout panics if it discovers an iframe without a nested browsing context. Under normal circumstances, this is reasonable, but it requires very tight synchronization between script, layout, the constellation and the compositor. In particular, if a layout is in progress when an iframe's browsing context is discarded, this can trigger panic. This PR fixes this in two ways: 1. Making the pipeline and browsing context ids optional in layout's representation of an iframe. 2. Shutting down layout before discarding a browsing context, rather than after. This is belt and braces. --- <!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: --> - [X] `./mach build -d` does not report any errors - [X] `./mach test-tidy` does not report any errors - [X] These changes fix #17482 and #18477 - [X] These changes do not require tests because the PR is fixing a panic caused by a race condition <!-- Also, please make sure that "Allow edits from maintainers" checkbox is checked, so that we can help you if you get stuck somewhere along the way.--> <!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. --> <!-- Reviewable:start --> --- This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/18514) <!-- Reviewable:end -->
This commit is contained in:
commit
c48ef50b72
6 changed files with 58 additions and 30 deletions
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@ -1024,8 +1024,8 @@ pub trait LayoutNodeHelpers {
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fn image_url(&self) -> Option<ServoUrl>;
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fn canvas_data(&self) -> Option<HTMLCanvasData>;
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fn svg_data(&self) -> Option<SVGSVGData>;
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fn iframe_browsing_context_id(&self) -> BrowsingContextId;
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fn iframe_pipeline_id(&self) -> PipelineId;
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fn iframe_browsing_context_id(&self) -> Option<BrowsingContextId>;
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fn iframe_pipeline_id(&self) -> Option<PipelineId>;
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fn opaque(&self) -> OpaqueNode;
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}
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@ -1175,16 +1175,16 @@ impl LayoutNodeHelpers for LayoutJS<Node> {
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.map(|svg| svg.data())
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}
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fn iframe_browsing_context_id(&self) -> BrowsingContextId {
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fn iframe_browsing_context_id(&self) -> Option<BrowsingContextId> {
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let iframe_element = self.downcast::<HTMLIFrameElement>()
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.expect("not an iframe element!");
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iframe_element.browsing_context_id().unwrap()
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iframe_element.browsing_context_id()
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}
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fn iframe_pipeline_id(&self) -> PipelineId {
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fn iframe_pipeline_id(&self) -> Option<PipelineId> {
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let iframe_element = self.downcast::<HTMLIFrameElement>()
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.expect("not an iframe element!");
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iframe_element.pipeline_id().unwrap()
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iframe_element.pipeline_id()
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}
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#[allow(unsafe_code)]
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@ -1750,10 +1750,35 @@ impl ScriptThread {
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load.pipeline_id == id
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});
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let document = self.documents.borrow_mut().remove(id);
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// We should never have a pipeline that's still an incomplete load,
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// but also has a Document.
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debug_assert!(idx.is_none() || document.is_none());
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// Remove any incomplete load.
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let chan = if let Some(idx) = idx {
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let load = self.incomplete_loads.borrow_mut().remove(idx);
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load.layout_chan.clone()
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} else if let Some(document) = self.documents.borrow_mut().remove(id) {
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} else if let Some(ref document) = document {
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document.window().layout_chan().clone()
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} else {
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return warn!("Exiting nonexistant pipeline {}.", id);
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};
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// We shut down layout before removing the document,
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// since layout might still be in the middle of laying it out.
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debug!("preparing to shut down layout for page {}", id);
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let (response_chan, response_port) = channel();
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chan.send(message::Msg::PrepareToExit(response_chan)).ok();
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let _ = response_port.recv();
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debug!("shutting down layout for page {}", id);
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chan.send(message::Msg::ExitNow).ok();
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self.script_sender.send((id, ScriptMsg::PipelineExited)).ok();
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// Now that layout is shut down, it's OK to remove the document.
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if let Some(document) = document {
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// We don't want to dispatch `mouseout` event pointing to non-existing element
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if let Some(target) = self.topmost_mouse_over_target.get() {
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if target.upcast::<Node>().owner_doc() == document {
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@ -1761,22 +1786,14 @@ impl ScriptThread {
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}
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}
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// We discard the browsing context after requesting layout shut down,
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// to avoid running layout on detached iframes.
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let window = document.window();
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if discard_bc == DiscardBrowsingContext::Yes {
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window.window_proxy().discard_browsing_context();
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}
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window.clear_js_runtime();
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window.layout_chan().clone()
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} else {
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return warn!("Exiting nonexistant pipeline {}.", id);
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};
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let (response_chan, response_port) = channel();
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chan.send(message::Msg::PrepareToExit(response_chan)).ok();
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debug!("shutting down layout for page {}", id);
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let _ = response_port.recv();
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chan.send(message::Msg::ExitNow).ok();
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self.script_sender.send((id, ScriptMsg::PipelineExited)).ok();
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}
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debug!("Exited pipeline {}.", id);
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}
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