The current build of kamailio (master) does not set `TLS_PTHREAD_MUTEX_SHARED` when building with `--with-openssl11` on systems with multiple versions of OpenSSL installed resulting in deadlocks in the TLS module.
All module Makefiles look for the `SSL_BUILDER` environment variable to provide a `pkg-config` command to find the `libssl` to link against. The variable is set to `pkg-config libssl11` by the RPM build when specifying `--with-openssl11`. Unfortunately, in `src/Makefile.defs`, there is an alternative way to look for a similar `pkg-config` command. However, this one always uses the `pkg-config libssl`, which - on systems with multiple versions of OpenSSL - usually points to OpenSSL 1.0.x. In turn the build thinks it will link against OpenSSL 1.0.x and will not set `KSR_PTHREAD_MUTEX_SHARED`.