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 <[email protected]>
> Cc: Juri Lelli <[email protected]>
> Cc: Vincent Guittot <[email protected]>
> Cc: Dietmar Eggemann <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Ben Segall <[email protected]>
> Cc: Mel Gorman <[email protected]>
> CC: Patrick Bellasi <[email protected]>
> Cc: Chris Redpath <[email protected]>
> Cc: Lukasz Luba <[email protected]>
> Cc: [email protected]Small nit below, otherwise: Reviewed-by: Valentin Schneider <[email protected]> > --- > 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. > }
