Re: futex(2) man page update help request

[H. Peter Anvin]

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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