Exiting immersive mode programmatically can lock up the browser

[jdm]

We had a report from a user that calling XrSession.end puts the browser into an unusable state after leaving immersive mode. We should try this out.

[paulrouget]

Calling session.end() crashes. At least with the emulator.

I uncommented this to test: https://github.com/servo/servo.org/blob/6c70d85ef880c7b25bbae406ee31d0d334bbe2f4/hl-home/webxr-ar.js#L112

https://github.com/servo/openxrs/blob/30d3bd0beddede0a7c958589b77f1125ffd23c92/openxr/src/space.rs#L116

simpleservo.dll!openxr::space::{{impl}}::drop(openxr::space::Space * self) Line 234	Unknown
simpleservo.dll!core::ptr::drop_in_place<openxr::space::Space>(openxr::space::Space *) Line 184	Unknown
simpleservo.dll!core::ptr::drop_in_place<webxr::openxr::OpenXrDevice>(webxr::openxr::OpenXrDevice *) Line 184	Unknown
simpleservo.dll!core::ptr::drop_in_place<webxr_api::session::SessionThread<webxr::openxr::OpenXrDevice>>(webxr_api::session::SessionThread<webxr::openxr::OpenXrDevice> *) Line 184	Unknown
simpleservo.dll!webxr_api::session::{{impl}}::spawn::{{closure}}<webxr::surfman_layer_manager::SurfmanGL,webxr::openxr::OpenXrDevice,closure-1>(webxr_api::session::{{impl}}::spawn::closure-0) Line 504	Unknown

[paulrouget]

@jdm can you reproduce with the device?

[paulrouget]

A crash doesn't lock up the browser, just restart it. So it looks like another type of issue.

[jdm]

I see exceptions on the device and then the script thread panics when trying to communicate with the webgl thread.

[jdm]

I do end up with a browser instance that is locked up, however.

[jdm]

We get a panic in the surfman Surface destructor:

 	simpleservo.dll!surfman::platform::windows::angle::surface::{{impl}}::drop(surfman::platform::windows::angle::surface::Surface * self) Line 89	Unknown	Symbols loaded.
 	simpleservo.dll!core::ptr::drop_in_place<surfman::platform::windows::angle::surface::Surface>(surfman::platform::windows::angle::surface::Surface *) Line 184	Unknown	Symbols loaded.
 	simpleservo.dll!core::ptr::drop_in_place<surfman::platform::windows::angle::surface::SurfaceTexture>(surfman::platform::windows::angle::surface::SurfaceTexture *) Line 184	Unknown	Symbols loaded.
 	simpleservo.dll!core::ptr::drop_in_place<core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture>>(core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture> *) Line 184	Unknown	Symbols loaded.
 	simpleservo.dll!core::ptr::drop_in_place<slice<core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture>>>(mut slice<core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture>>*) Line 184	Unknown	Symbols loaded.
 	simpleservo.dll!alloc::vec::{{impl}}::drop<core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture>>(alloc::vec::Vec<core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture>> * self) Line 2426	Unknown	Symbols loaded.
 	simpleservo.dll!core::ptr::drop_in_place<alloc::vec::Vec<core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture>>>(alloc::vec::Vec<core::option::Option<surfman::platform::windows::angle::surface::SurfaceTexture>> *) Line 184	Unknown	Symbols loaded.
 	simpleservo.dll!core::ptr::drop_in_place<webxr::openxr::OpenXrLayer>(webxr::openxr::OpenXrLayer *) Line 184	Unknown	Symbols loaded.
 	simpleservo.dll!webxr::openxr::{{impl}}::destroy_layer(webxr::openxr::OpenXrLayerManager * self, surfman::platform::windows::angle::device::Device * device, webxr_api::layer::mut GLContexts<webxr::surfman_layer_manager::SurfmanGL>* contexts, webxr_api::layer::ContextId context_id, webxr_api::layer::LayerId layer_id) Line 580	Unknown	Symbols loaded.
>	simpleservo.dll!canvas::webgl_thread::WebXRBridge::destroy_layer(canvas_traits::webgl::WebXRLayerManagerId self, surfman::platform::windows::angle::device::Device * manager_id, webxr_api::layer::mut GLContexts<webxr::surfman_layer_manager::SurfmanGL>* device, webxr_api::layer::ContextId contexts, webxr_api::layer::LayerId context_id) Line 3218	Unknown	Symbols loaded.
 	simpleservo.dll!canvas::webgl_thread::WebGLThread::handle_webxr_command(canvas_traits::webgl::WebXRCommand self) Line 452	Unknown	Symbols loaded.
 	simpleservo.dll!canvas::webgl_thread::WebGLThread::handle_msg(canvas_traits::webgl::WebGLMsg self, canvas_traits::webgl_channel::WebGLChan * msg) Line 408	Unknown	Symbols loaded.
 	simpleservo.dll!canvas::webgl_thread::WebGLThread::process() Line 326	Unknown	Symbols loaded.
 	simpleservo.dll!canvas::webgl_thread::{{impl}}::run_on_own_thread::{{closure}}(canvas::webgl_thread::{{impl}}::run_on_own_thread::closure-0) Line 318	Unknown	Symbols loaded.
 	simpleservo.dll!std::sys_common::backtrace::__rust_begin_short_backtrace<closure-0,()>(canvas::webgl_thread::{{impl}}::run_on_own_thread::closure-0 f) Line 131	Unknown	Symbols loaded.
 	simpleservo.dll!std::thread::{{impl}}::spawn_unchecked::{{closure}}::{{closure}}<closure-0,()>(std::thread::{{impl}}::spawn_unchecked::{{closure}}::closure-0) Line 476	Unknown	Symbols loaded.
 	simpleservo.dll!std::panic::{{impl}}::call_once<(),closure-0>(std::panic::AssertUnwindSafe<closure-0> self) Line 319	Unknown	Symbols loaded.
 	simpleservo.dll!std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure-0>,()>(unsigned char * data) Line 350	Unknown	Symbols loaded.
 	simpleservo.dll!_ZN3std9panicking3try8do_catch17hfe925d2c4cc976a2E�()	Unknown	Symbols loaded.
 	simpleservo.dll!std::panicking::try<(),std::panic::AssertUnwindSafe<closure-0>>(std::panic::AssertUnwindSafe<closure-0> f) Line 325	Unknown	Symbols loaded.
 	simpleservo.dll!std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure-0>,()>(std::panic::AssertUnwindSafe<closure-0> f) Line 394	Unknown	Symbols loaded.
 	simpleservo.dll!std::thread::{{impl}}::spawn_unchecked::{{closure}}<closure-0,()>(std::thread::{{impl}}::spawn_unchecked::closure-0) Line 474	Unknown	Symbols loaded.
 	simpleservo.dll!core::ops::function::FnOnce::call_once<closure-0,()>(std::thread::{{impl}}::spawn_unchecked::closure-0 *) Line 233	Unknown	Symbols loaded.
 	simpleservo.dll!_ZN3std3sys7windows6thread6Thread3new17h5ec4098bc2c5c4dcE�()	Unknown	Symbols loaded.
 	ntdll.dll!00007ffbb3169e18()	Unknown	No symbols loaded.

[jdm]

I submitted servo/webxr#186 which allows me to use the browser as expected after calling session.end().