Re: any fairness in NTPL pthread mutexes?

Lee Revell
2005-10-31T22:10:51Z

On Mon, 2005-10-31 at 13:06 -0500, Lee Revell wrote:
> On Mon, 2005-10-31 at 11:57 -0600, 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.)?
>
> I believe it's currently FIFO in violation of POSIX which specifies
> priority based wakeup. AIUI one of the main goals of the realtime &
> robust mutexes work is to fix this.

Sorry this is wrong - the current behavior is allowed by POSIX for
SCHED_OTHER but not SCHED_FIFO or _RR.

Lee