When shutting down a content process, we call `Close` on the `IToplevelProtocol`. This causes the MessageChannel to be `Close`-ed, which in turn sends a `GOODBYE_MESSAGE`: https://searchfox.org/mozilla-central/rev/876022232b15425bb9efde189caf747823b39567/ipc/glue/MessageChannel.cpp#2852 This message is intercepted on the I/O thread in the content process, before any code is informed in content, and used to set the `mChannelState` property to `ChannelClosing`: https://searchfox.org/mozilla-central/rev/876022232b15425bb9efde189caf747823b39567/ipc/glue/MessageChannel.cpp#1176 Once this state has been set, which is performed as soon as the message is received, whether or not other messages have been processed yet, no messages can be sent back to the parent process. This is usually what causes the 'Too late to send/recv' message spam in the console, as we're still trying to send messages at this time. Usually this is fine - the message send fails, but we gracefully recover, and the process begins shutting down like normal. Unfortunately, child actor constructors currently have code automatically generated in them which causes a process crash if the send fails. As it's impossible for the main thread to know that the channel has been closed ahead of time (due to this happening out-of-band), we can then cause random content process crashes during shutdown due to actor construction. The obvious fix which I'm taking in this patch is to relax this assertion to instead gracefully fail & destroy the actor if the message send failed on both sides, rather than just content. This caused the crashes in bug 1487249.

When shutting down a content process, we call `Close` on the `IToplevelProtocol`. This causes the MessageChannel to be `Close`-ed, which in turn sends a `GOODBYE_MESSAGE`: https://searchfox.org/mozilla-central/rev/876022232b15425bb9efde189caf747823b39567/ipc/glue/MessageChannel.cpp#2852 This message is intercepted on the I/O thread in the content process, before any code is informed in content, and used to set the `mChannelState` property to `ChannelClosing`: https://searchfox.org/mozilla-central/rev/876022232b15425bb9efde189caf747823b39567/ipc/glue/MessageChannel.cpp#1176 Once this state has been set, which is performed as soon as the message is received, whether or not other messages have been processed yet, no messages can be sent back to the parent process. This is usually what causes the 'Too late to send/recv' message spam in the console, as we're still trying to send messages at this time. Usually this is fine - the message send fails, but we gracefully recover, and the process begins shutting down like normal. Unfortunately, child actor constructors currently have code automatically generated in them which causes a process crash if the send fails. As it's impossible for the main thread to know that the channel has been closed ahead of time (due to this happening out-of-band), we can then cause random content process crashes during shutdown due to actor construction. The obvious fix which I'm taking in this patch is to relax this assertion to instead gracefully fail & destroy the actor if the message send failed on both sides, rather than just content.

Pushed by nika@thelayzells.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/c3fe435e473a Don't crash when constructing actor during content shutdown, r=jld

Backed out 13 changesets (bug 1500948, bug 1509362, bug 1509591, bug 1448426, bug 1500949, bug 1487249, bug 1509930, bug 1500950, bug 1500944) for causing crashes and assertion failures on PBackgroundParent.cpp:696 CLOSED TREE Backout revision https://hg.mozilla.org/integration/mozilla-inbound/rev/9bfe29337ffe3d93cd060077e2e999e72bb9b7cf Failed push https://treeherder.mozilla.org/#/jobs?repo=mozilla-inbound&resultStatus=testfailed%2Cbusted%2Cexception&classifiedState=unclassified&selectedJob=214255312&revision=c3fe435e473a463fbc22d4afa531bdedb757079c Failure logs: https://treeherder.mozilla.org/logviewer.html#?job_id=214255312&repo=mozilla-inbound https://treeherder.mozilla.org/logviewer.html#?job_id=214255794&repo=mozilla-inbound https://treeherder.mozilla.org/logviewer.html#?job_id=214249038&repo=mozilla-inbound https://treeherder.mozilla.org/logviewer.html#?job_id=214249630&repo=mozilla-inbound :Nika Layzell Could you please take a look?

Pushed by nika@thelayzells.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/7e23a1b90335 Don't crash when constructing actor during content shutdown, r=jld

Pushed by nika@thelayzells.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/1c1f445a9b6a Don't crash when constructing actor during content shutdown, r=jld