| Date | Wed, 14 May 2014 17:28:32 -0700 | From | "H. Peter Anvin" <> | Subject | Re: futex(2) man page update help request |
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On 05/14/2014 01:56 PM, Davidlohr Bueso wrote: >> >>> However, unless I'm sorely mistaken, the larger problem is that glibc >>> removed the futex() call entirely, so these man pages don't describe >> >> I don't think futex() ever was in glibc--that's by design, and >> completely understandable: no user-space application would want to >> directly use futex(). > > That's actually not quite true. There are plenty of software efforts out > there that use futex calls directly to implement userspace serialization > mechanisms as an alternative to the bulky sysv semaphores. I worked > closely with an in-memory DB project that makes heavy use of them. Not > everyone can simply rely on pthreads. >
More fundamentally, futex(2), like clone(2), are things that can be legitimately by user space without automatically breaking all of glibc. There are some other things where that is *not* true, because glibc relies on being able to mediate all accesses to a kernel facility, but not here.
-hpa
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