On the NPTL process [LWN.net]

At the first encounter, the Native POSIX Thread Library looks like ideal grist for the Red Hat basher's mill. The library appears to have sprung fully formed from the head of glibc maintainer (and Red Hat employee) Ulrich Drepper, who has made his plans clear:

Unless major flaws in the design are found this code is intended to become the standard POSIX thread library on Linux system and it will be included in the GNU C library distribution.

Installing this library is not easy, since it requires some fairly bleeding-edge software: a 2.5.36 kernel, gcc 3.2, and a current glibc 2.3 snapshot. In fact, the "only environment known to date which works" is an updated version of the "(Null)" Red Hat beta. And, of course, this development has seemingly ignored the longstanding efforts of the Next Generation POSIX Threading project, which is at release 2.0.2.

A certain (relatively small) amount of grumbling along these lines has been seen on the net. But it's uncalled for.

NPTL was developed independently from NGPT for a straightforward reason: the NPTL developers wanted to try a very different approach. NGPT is designed around the M:N model, which, as noted above, NPTL avoids. There was no way to integrate the NPTL approach into NGPT without massive changes. The NPTL developers did, however, work with the NGPT hackers with regard to the kernel changes; those enhancements will benefit both projects in the end.

A new library at version 0.1 can probably be forgiven for using bleeding-edge tools; it is a bleeding-edge tool, after all. By the time NPTL has stabilized, the environments available to users will have caught up substantially. Ingo Molnar, author of the kernel side of the NPTL work, tells us that he intends to backport the kernel changes to the 2.4 kernel once things have stabilized in 2.5. (Whether 2.4 maintainer Marcelo Tosatti will accept them is a separate issue, of course).

And, in the end, this development has been going on for less than two months - it is a very new initiative.

This development shows some of the best aspects of the free software model. Two hackers with some good ideas have proved those ideas in the way the community accepts best: with code. We will all benefit from this work.

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