Messages in this thread | | | Date | Fri, 15 Mar 2002 09:41:05 +0100 | From | Martin Wirth <> | Subject | Re: [PATCH] Futexes IV (Fast Lightweight Userspace Semaphores) |
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Rusty Russell wrote:
> >Discussions with Ulrich have reaffirmed my opinion that pthreads are >crap. Hence I'm not all that tempted to warp the (nice, clean, >usable) futex code too far to meet pthreads' wierd needs. > Crap or not, there are tons of software based on pthreads and at least the NGPT team says that Linus agreed to implement for necessary kernel-infrastructure for a full, fast pthread implementation.
Now, if you want to implement mutexes and condition variables with the attribute PTHREAD_PROCESS_SHARED then you need some functionality like the futexes. Or NGPT will add his own syscalls to handle these things, which is simply unnecessary double functionality.
> >However, it's not too hard to implement condition variables using an >unavailable mutex, if we go for "full" semaphores: ie. not just >mutexes. It requires a bit more of a stretch for kernel atomic ops... > A full semaphore is nice, but not a full replacement for a waitqueue (or a pthread condition variable brr..). For the semaphore you always have to assure that the ups and downs are balanced, what is not the case for the condition variable.
Martin
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