Messages in this thread | | | Date | Thu, 16 Apr 2020 13:41:31 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] sched/core: Fix reset-on-fork from RT with uclamp |
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On Thu, Apr 16, 2020 at 01:03:16PM +0200, Dietmar Eggemann wrote: > On 16.04.20 10:59, Quentin Perret wrote: > > uclamp_fork() resets the uclamp values to their default when the > > reset-on-fork flag is set. It also checks whether the task has a RT > > policy, and sets its uclamp.min to 1024 accordingly. However, during > > reset-on-fork, the task's policy is lowered to SCHED_NORMAL right after, > > hence leading to an erroneous uclamp.min setting for the new task if it > > was forked from RT. > > > > Fix this by removing the unnecessary check on rt_task() in > > uclamp_fork() as this doesn't make sense if the reset-on-fork flag is > > set. > > > > Fixes: 1a00d999971c ("sched/uclamp: Set default clamps for RT tasks") > > Reported-by: Chitti Babu Theegala <ctheegal@codeaurora.org> > > Reviewed-by: Patrick Bellasi <patrick.bellasi@matbug.net> > > Signed-off-by: Quentin Perret <qperret@google.com> > > --- > > Changes in v2: > > - Added missing 'Fixes:' tag (Patrick) > > - Removed unnecessary local variable (Doug, Patrick) > > --- > > kernel/sched/core.c | 9 ++------- > > 1 file changed, 2 insertions(+), 7 deletions(-) > > > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > > index 3a61a3b8eaa9..9a2fbf98fd6f 100644 > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -1232,13 +1232,8 @@ static void uclamp_fork(struct task_struct *p) > > return; > > > > for_each_clamp_id(clamp_id) { > > - unsigned int clamp_value = uclamp_none(clamp_id); > > - > > - /* By default, RT tasks always get 100% boost */ > > - if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) > > - clamp_value = uclamp_none(UCLAMP_MAX); > > - > > - uclamp_se_set(&p->uclamp_req[clamp_id], clamp_value, false); > > + uclamp_se_set(&p->uclamp_req[clamp_id], > > + uclamp_none(clamp_id), false); > > } > > } > > LGTM. > > Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Thanks guys!
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