Re: any fairness in NTPL pthread mutexes?

Robert Hancock
2005-11-01T03:52:52Z

Christopher Friesen wrote:
>
> I'm using NPTL.
>
> If I have a pthread mutex currently owned by a task, and two other tasks
> try to lock it, when the mutex is unlocked, are there any rules about
> the order in which the waiting tasks get the mutex (ie priority, FIFO,
> etc.)?
>

Not in the pthread spec (at least not for normal SCHED_OTHER tasks), and
Linux/glibc don't really provide any either. In particular, if one
thread unlocks a mutex and immediately tries to relock, there is no
guarantee that any other thread waiting on the mutex will be able to get
in and lock it before the first thread can relock.

--
Robert Hancock Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/