From: Quentin Perret qperret@google.com
commit eaf5a92ebde5bca3bb2565616115bd6d579486cd upstream.
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 Signed-off-by: Quentin Perret qperret@google.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Patrick Bellasi patrick.bellasi@matbug.net Reviewed-by: Dietmar Eggemann dietmar.eggemann@arm.com Link: https://lkml.kernel.org/r/20200416085956.217587-1-qperret@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- kernel/sched/core.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-)
--- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1239,13 +1239,8 @@ static void uclamp_fork(struct task_stru 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); } }