dnsdist: Fix a hang when removing a server with more than one socket #9900
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There was a lock starvation issue when removing a server with more than one socket in use (`sockets` greater than 1 on the corresponding `newServer` directive), because the mutex protecting the sockets array would never be released long enough by the responder thread to allow the thread stopping the server to acquire it. This commit fixes that by marking the server as stopped right away, before acquiring the lock, and also making sure that the responder thread is woken up regularly (every second, even without any query to process) and that it checks whether the server has been stopped just after that. The issue was introduced in be55a20, and backported to 1.5.1 in f0d4831.
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Short description
There was a lock starvation issue when removing a server with more than one socket in use (
socketsgreater than 1 on the correspondingnewServerdirective), because the mutex protecting the sockets array would never be released long enough by the responder thread to allow the thread stopping the server to acquire it.This commit fixes that by marking the server as stopped right away, before acquiring the lock, and also making sure that the responder thread is woken up regularly (every second, even without any query to process) and that it checks whether the server has been stopped just after that.
The issue was introduced in be55a20, and backported to 1.5.1 in f0d4831.
Checklist
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