Apparently Solaris uses park() to the same effect. I can't readily find a history of either. Anyone know which came first, Solaris or Linux? In part I'm reacting to @Animats statement that UNIX is behind.
Being an old OS hacker of that day I was about for the release of both;
Linux was 1991 - as a minimal monolithic single arch student level kludge made from studying SunOS API calls and the MINIX project.
Solaris was 1993 .. a succusor to SunOS and a turn away from the SunOS BSD roots towards UNIX System V Release 4.
Both Linux and Solaris had deep prior art roots in the "Unix-like" sphere, many ideas cropped up over there originally but only really gained traction somewhere else.
( Other ideas of that time, such as capability based permissions, never really took off until decades later )
Sorry, I didn't mean when did Linux and Solaris first see light of day.
I meant, when did the futex (linux) and park() (Solaris) functionality become available in both? Some Linux things have an [uncredited] history as a Solaris feature first.
<doh> my bad, skimming too fast, reading too little.
To the best of my recollection, with some links I see that back this:
Futex appeared in Linux circa 2002 ( late kernel ver 2.5 series ), (Net) BSD _lwp_park() appeared circa 2009 but ... I have an inkling it popped up earlier in sources I don't have online access to right now (archived drives | tapes in a shed some distance away)
This post 2000 era is right when I moved away from heavy Sun workstation usage and low level tinkering and into other domains.
> capability based permissions, never really took off until decades later
Didn't all the unices of the day have C2-secure (and even tighter) "orange book" versions? Windows as well I believe. And definitely some other unices. That's so long ago I don't recall but didn't starting at C2 require MAC and this implies some kind of privilege system.
Solaris has had privileges (analogous to Linux capabilities) since 2005. Looks like Linux had it since 1999 but of more limited scope until 2008 when it got extended.
I got into both Linux and SunOS around 1996. At the time, I got the impression (perhaps correctly so) that Linux was a "play thing" and mostly good for small businesses, while SunOS was the only thing that would properly scale to the type of volume an Internet business could expect.
As far as I can tell they are not the same abstraction.
park/unpark simply remove the thread from the run queue and require userspace to keep the waitqueue and identify which thread to wakeup. The semantics of futex is that the kernel will maintain the waitqueue. The advantage is that futex can be used across processes, not just threads and are possibly easier, on the other hand, high performance signaling primitives implementations probably want to maintain the waitqueue in userspace anyway, so park/unpark might be a better, if lower level, primitive.
I actually meant setpark but was being a little too concise. Yes park/unpark without setpark is not the same thing. But does setpark not offer the same functionality as futexes? I can find various references, university coursework mostly, that either imply or outright say these are the same thing.
That said, I was completely unaware that futex can work across processes as IPC! Sorry I'm being lazy here but I don't know if park/unpark/setpark offer that -- I doubt it. However on Solaris you have doors which is an ultrafast IPC.
