Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH 1/2] sched/uclamp: Fix initialization of strut uclamp_rq | Date | Fri, 19 Jun 2020 11:36:17 +0100 |
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On 18/06/20 20:55, Qais Yousef wrote: > struct uclamp_rq was zeroed out entirely in assumption that in the first > call to uclamp_rq_inc() they'd be initialized correctly in accordance to > default settings. > > But when next patch introduces a static key to skip > uclamp_rq_{inc,dec}() until userspace opts in to use uclamp, schedutil > will fail to perform any frequency changes because the > rq->uclamp[UCLAMP_MAX].value is zeroed at init and stays as such. Which > means all rqs are capped to 0 by default. > > Fix it by making sure we do proper initialization at init without > relying on uclamp_rq_inc() doing it later. > > Fixes: 69842cba9ace ("sched/uclamp: Add CPU's clamp buckets refcounting") > Signed-off-by: Qais Yousef <qais.yousef@arm.com> > Cc: Juri Lelli <juri.lelli@redhat.com> > Cc: Vincent Guittot <vincent.guittot@linaro.org> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: Steven Rostedt <rostedt@goodmis.org> > Cc: Ben Segall <bsegall@google.com> > Cc: Mel Gorman <mgorman@suse.de> > CC: Patrick Bellasi <patrick.bellasi@matbug.net> > Cc: Chris Redpath <chrid.redpath@arm.com> > Cc: Lukasz Luba <lukasz.luba@arm.com> > Cc: linux-kernel@vger.kernel.org
Small nit below, otherwise: Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
> --- > kernel/sched/core.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index a43c84c27c6f..e19d2b915406 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -1248,6 +1248,20 @@ static void uclamp_fork(struct task_struct *p) > } > } > > +static void __init init_uclamp_rq(struct rq *rq) > +{ > + enum uclamp_id clamp_id; > + struct uclamp_rq *uc_rq = rq->uclamp; > + > + for_each_clamp_id(clamp_id) { > + memset(uc_rq[clamp_id].bucket, > + 0, > + sizeof(struct uclamp_bucket)*UCLAMP_BUCKETS); > + > + uc_rq[clamp_id].value = uclamp_none(clamp_id); > + } > +} > + > static void __init init_uclamp(void) > { > struct uclamp_se uc_max = {}; > @@ -1257,8 +1271,7 @@ static void __init init_uclamp(void) > mutex_init(&uclamp_mutex); > > for_each_possible_cpu(cpu) { > - memset(&cpu_rq(cpu)->uclamp, 0, > - sizeof(struct uclamp_rq)*UCLAMP_CNT); > + init_uclamp_rq(cpu_rq(cpu)); > cpu_rq(cpu)->uclamp_flags = 0;
That flags assignment ought to be squashed in the init function as well - and actually you do that in patch 2, so I suppose that's a rebase accident.
> }
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