Linux approach is very fast, and convenient for most cases. The only regret I have (had) is that working in that way, it brings some problems like different behavior on signal() versus most POSIX implementations (e.g. signal handlers on a thread not being the main one, etc.). Not really a problem, but a bit annoying when porting UNIX code to Linux.
The signal behaviour required for POSIX threads is available by specifying the CLONE_SIGHAND flag to clone(2). This is what the glibc pthreads implementation does.
Linux did once have a pthreads implementation that wasn't POSIX-conforming in these sorts of areas ("LinuxThreads"), but those days are long behind us. NPTL has been the standard for at least 10 years now.
