Messages in this thread | | | Subject | Re: [PATCH 2/2] sched: allow users with rtprio rlimit to change from SCHED_IDLE policy | From | Peter Zijlstra <> | Date | Thu, 24 Feb 2011 12:49:27 +0100 |
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On Wed, 2011-02-23 at 13:28 -0800, Darren Hart wrote: > From: Darren Hart <dvhart@linux.intel.com> > Date: Thu, 17 Feb 2011 15:37:07 -0800 > Subject: [PATCH] sched: allow users with sufficient RLIMIT_NICE to change from SCHED_IDLE policy > > The current scheduler implementation returns -EPERM when trying to change from > SCHED_IDLE to SCHED_OTHER or SCHED_BATCH.
> Since SCHED_IDLE is considered to be > equivalent to a nice 20,
Well, its not quite equivalent, its actually 5 times lighter still and the preemption behaviour is slightly different as you've found ;-)
> changing to another policy should be allowed provided > the RLIMIT_NICE is accounted for. > > This patch allows the following test-case to pass with RLIMIT_NICE=40, but still > fail with RLIMIT_NICE=10 when the calling process is run from a typical shell > (nice 0, or 20 in rlimit terms).
> > Signed-off-by: Darren Hart <dvhart@linux.intel.com> > CC: Peter Zijlstra <peterz@infradead.org> > CC: Ingo Molnar <mingo@elte.hu> > CC: Richard Purdie <richard.purdie@linuxfoundation.org> > --- > kernel/sched.c | 11 +++++++---- > 1 files changed, 7 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched.c b/kernel/sched.c > index 18d38e4..9bf6284 100644 > --- a/kernel/sched.c > +++ b/kernel/sched.c > @@ -4822,12 +4822,15 @@ recheck: > param->sched_priority > rlim_rtprio) > return -EPERM; > } > + > /* > + * Treat SCHED_IDLE as nice 20. Only allow a switch to > + * SCHED_NORMAL if the RLIMIT_NICE would normally permit it. > */ > + if (p->policy == SCHED_IDLE && policy != SCHED_IDLE) { > + if (!can_nice(p, TASK_NICE(p))) > + return -EPERM; > + } > > /* can't change other user's priorities */ > if (!check_same_owner(p))
Looks fine, thanks!
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