Emulating Windows system calls, take 2

Posted Jul 23, 2020 21:02 UTC (Thu) by BenHutchings (subscriber, #37955)
In reply to: Emulating Windows system calls, take 2 by nix
Parent article: Emulating Windows system calls, take 2

This is not what happened with threads. The kernel APIs that supported LinuxThreads were not sufficient to build a compliant POSIX threads implementation. The New POSIX Threads Library (NPTL) that eventually replaced LinuxThreads required additional kernel APIs.

Emulating Windows system calls, take 2

Posted Jul 24, 2020 22:08 UTC (Fri) by nix (subscriber, #2304) [Link]

It did -- but this wasn't done the way (say) Solaris did it, by piling the entire threading abstraction into the kernel and complicating the bejeezus out of everything. Instead we got away with a few relatively simple and noninvasive things: thread groups, a bit of tweaking to signal handling (which was painful, sure, but much less painful than almost everything else around signal handling already was and is), futexes, and some nice souping up to PID allocation so you could have silly numbers of them.

(And a good few of those abstractions were, I vaguely recall, there *already*, and used by LinuxThreads: tgids, for instance. I'm sure futexes were new for NPTL though.)