While that would address the "failed to set priority" warning, that is not the real issue faced by the OP (and can in fact usually be ignored). Instead, the camera failed to open because "Xiron OS failed to create a mutex".
In my case, rebuilding the (Android-x86-supplied) kernel to add support for "System V IPC" solved the issue. Specifically, the OpenNI library attempts to create an IPC semaphore for use as a mutex between multiple processes accessing the camera.
Stock Linux kernel (including the one in Ubuntu) should already have IPC support. Perhaps the OP had built a custom kernel as well?