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Each request references the router process structure that owns all memory maps. The process structure has a reference counter; each request increases the counter to lock the structure in memory until request processing ends. Incoming and outgoing buffers reference memory maps that the process owns, so the process structure should be released only when all buffers are released to avoid invalid memory access and a crash. This describes the libunit library mechanism used for application processes. The background of this issue is as follows: The issue was found on buildbot when the router crashed during Java websocket tests. The Java application receives a notification from the master process; when the notification is processed, libunit deletes the process structure from its process hash and decrements the use counter; however, active websocket connections maintain their use counts on the process structure. After that, when the master process is stopping the application, libunit releases active websocket connections. At this point, it's important to release the connections' memory buffers before the corresponding process structure and all shared memory segments are released.
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