This is a note to let you know that I've just added the patch titled
sched/core: Fix reset-on-fork from RT with uclamp
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-core-fix-reset-on-fork-from-rt-with-uclamp.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ba8a5875bc86746f921bfc3230d777100e2afecd
Author: Quentin Perret <qperret@xxxxxxxxxx>
Date: Thu Apr 16 09:59:56 2020 +0100
sched/core: Fix reset-on-fork from RT with uclamp
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@xxxxxxxxxxxxxx>
Signed-off-by: Quentin Perret <qperret@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Patrick Bellasi <patrick.bellasi@xxxxxxxxxx>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Link: https://lkml.kernel.org/r/20200416085956.217587-1-qperret@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 195d0019e6bb5..e99d326fa5693 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1233,13 +1233,8 @@ 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);
}
}
