On 07/28/2015 11:03 PM, Thomas Gleixner wrote:

On Tue, 28 Jul 2015, Peter Zijlstra wrote:

quoted

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

quoted

quoted

       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'.

Indeed.
 

quoted

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?

I think so.

So, no change to this piece of text then?

Cheers,

Michael


-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/