Date: Sat, 5 Mar 2016 19:14:34 -0500 From: Pedro Giffuni <pfg@...eBSD.org> To: Rich Felker <dalias@...c.org> Cc: musl@...ts.openwall.com Subject: Re: FreeBSD's Google Summer of Code 2016 On 03/05/16 18:32, Rich Felker wrote: > On Sat, Mar 05, 2016 at 05:41:25PM -0500, Pedro Giffuni wrote: >> First of all, great to hear there is interest on the musl side too. >> >> I think the biggest precedent of porting linux-oriented C libraries >> came from Debian's kFreeBSD. We accomodated a little by for them >> by defining __FreeBSD_kernel__ in sys/param.h. >> >> While using the optional linux-abi futex in FreeBSD could be an option, >> it is not really the cleanest option. The Debian guys did a port of >> NPTL using regular pthreads: >> Of course I ahould have meant "based on regular FreeBSD kernel services". >> http://thread.gmane.org/gmane.linux.debian.ports.bsd/11702 >> >> I am certain this will require more research but it would be useful >> for other ports as well. > We could ask Petr Salinger for the details, but I am pretty sure FreeBSD has the required functionality natively. > Glibc/NPTL has a lot of what I'd call "gratuitous abstraction" (like > the lll stuff) in their pthread primitives which makes this > "possible". I call it gratuitous because it's really really hard to > achieve correct implementations of the pthread sync primitives that > don't have serious corner-case bugs, and it's unlikely that their > abstractions actually suffice to make correct alternate > implementations. > > musl does not have any such abstraction. We require a compare-and-swap > operation or equivalent on which arbitrary atomic operations can be > constructed, a futex or equivalent operation that's roughly > while(*addr==expected) sleep(), and implement all the sync primitives > just once on top of these. > I am not a threading expert (or even a CS guy), but it sounds like mutex(9) with condvar(9) would do : https://www.freebsd.org/doc/en/books/arch-handbook/locking.html Cheers, Pedro.  You can watch the manpages here: https://www.freebsd.org/cgi/man.cgi
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