Are BSD/Posix sockets reentrant?

Can several threads operate on the same socket descriptor, i.e ac开发者_如何学运维cept(sock_fd) at the same time without concern?

The platform I'm mostly interested in is POSIX/Linux.

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Yes, they are "reentrant" - kernel locks the socket structure while working on it (see Linux accept source for example), so only one thread would get the client connection.