dnsdist: Prevent race while creating new TCP worker threads #4764
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We try very hard to avoid using locks, but we need to prevent two threads inserting into the TCP workers vector concurrently. While this can't happen at runtime since the healthcheck thread is the only one calling `g_tcpclientthreads->addTCPClientThread()`, this might happen at startup time because we start the TCP acceptor threads one after another and they all call it once. This might result, for example, in one vector entry being overwritten and another one remaining value-initialized to zero.
rgacogne
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Dec 14, 2016
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Short description
We try very hard to avoid using locks, but we need to prevent two threads inserting into the TCP workers vector concurrently. While this can't happen at runtime since the healthcheck thread is the only one calling
g_tcpclientthreads->addTCPClientThread(), this might happen at startup time because we start the TCP acceptor threads one after another and they all call it once. This might result, for example, in one vector entry being overwritten and another one remaining value-initialized to zero.Reported and very kindly investigated by @paddg (thanks!).
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