Re: Next round: revised futex(2) man page for review

[Peter Zijlstra <peterz@infradead.org>]

On Tue, Jul 28, 2015 at 10:23:51PM +0200, Thomas Gleixner wrote:

> >        FUTEX_WAKE (since Linux 2.6.0)
> >               This  operation  wakes at most val of the waiters that are
> >               waiting (e.g., inside FUTEX_WAIT) on the futex word at the
> >               address  uaddr.  Most commonly, val is specified as either
> >               1 (wake up a single waiter) or INT_MAX (wake up all  wait‐
> >               ers).   No  guarantee  is provided about which waiters are
> >               awoken (e.g., a waiter with a higher  scheduling  priority
> >               is  not  guaranteed to be awoken in preference to a waiter
> >               with a lower priority).
> 
> That's only correct up to Linux 2.6.21.
> 
> Since 2.6.22 we have a priority ordered wakeup. For SCHED_OTHER
> threads this takes the nice level into account. Threads with the same
> priority are woken in FIFO order.

Maybe don't mention the effects of SCHED_OTHER, order by nice value is
'wrong'.

Also, this code seems to use plist, which means it won't do the right
thing for SCHED_DEADLINE either.

Do we want to go fix that?