IIUC it looks as if [we store the destination thread used to dispatch the event](https://searchfox.org/mozilla-central/rev/b1b87f95ecea00828298d1b3cd3d8718f9fcc3fc/ipc/glue/MessageChannel.cpp#2110). I wonder if we are in a situation like [described here](https://searchfox.org/mozilla-central/rev/b1b87f95ecea00828298d1b3cd3d8718f9fcc3fc/ipc/glue/BackgroundImpl.cpp#964-968) and managed to dispatch that runnable to the old background thread in the short time window between the shutdown runnable ran on the old background thread and the thread really ended to accept events. This use of `mWorkerThread` was introduced by bug 1719577 which lived in IPC. Moving there for further investigation.
Bug 1911703 Comment 3 Edit History
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IIUC it looks as if [we store the destination thread used to dispatch the crashing event](https://searchfox.org/mozilla-central/rev/b1b87f95ecea00828298d1b3cd3d8718f9fcc3fc/ipc/glue/MessageChannel.cpp#2110). I wonder if we are in a situation like [described here](https://searchfox.org/mozilla-central/rev/b1b87f95ecea00828298d1b3cd3d8718f9fcc3fc/ipc/glue/BackgroundImpl.cpp#964-968) and managed to dispatch that runnable to the old background thread in the short time window between the shutdown runnable ran on the old background thread and the thread really ended to accept events. This use of `mWorkerThread` was introduced by bug 1719577 which lived in IPC. Moving there for further investigation.