previous pluginloader.exe process won't exit when I restart firefox

[lzy]

I am using pipelight on archlinux x86
If I close firefox, pluginloader.exe processes should exit as the firefox process ends.
however, if I restart firefox (for example, install a new add-on that requires restart), the previous pluginloader.exe processes keep running and new pluginloader.exe processes appears.
so if I restart firefox for many times, the pluginloader.exe processes amount will keep growing

[Michael Müller (mqchael)]

The Pipelight library, which is loaded by the browser, communicates through a pipe with the pluginloader.exe. The pluginloader.exe process will terminate itself as soon as the pipe is closed by the other side, so the number of process shouldn't grow unless the corresponding linux process is still alive. Firefox loads the plugins into a process called plugin-container, so you should take a look how many instances of plugin-container are still alive.

[lzy (2273520349-3)]

I am sure there is only a single instance
https://img42.com/ORqw2