This is a note to let you know that I've just added the patch titled
sched/rt: Disable RT_RUNTIME_SHARE by default
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-rt-disable-rt_runtime_share-by-default.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.
>From 2586af1ac187f6b3a50930a4e33497074e81762d Mon Sep 17 00:00:00 2001
From: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Date: Mon, 21 Sep 2020 16:39:49 +0200
Subject: sched/rt: Disable RT_RUNTIME_SHARE by default
From: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
commit 2586af1ac187f6b3a50930a4e33497074e81762d upstream.
The RT_RUNTIME_SHARE sched feature enables the sharing of rt_runtime
between CPUs, allowing a CPU to run a real-time task up to 100% of the
time while leaving more space for non-real-time tasks to run on the CPU
that lend rt_runtime.
The problem is that a CPU can easily borrow enough rt_runtime to allow
a spinning rt-task to run forever, starving per-cpu tasks like kworkers,
which are non-real-time by design.
This patch disables RT_RUNTIME_SHARE by default, avoiding this problem.
The feature will still be present for users that want to enable it,
though.
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Wei Wang <wvw@xxxxxxxxxx>
Link: https://lkml.kernel.org/r/b776ab46817e3db5d8ef79175fa0d71073c051c7.1600697903.git.bristot@xxxxxxxxxx
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/features.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -77,7 +77,7 @@ SCHED_FEAT(WARN_DOUBLE_CLOCK, false)
SCHED_FEAT(RT_PUSH_IPI, true)
#endif
-SCHED_FEAT(RT_RUNTIME_SHARE, true)
+SCHED_FEAT(RT_RUNTIME_SHARE, false)
SCHED_FEAT(LB_MIN, false)
SCHED_FEAT(ATTACH_AGE_LOAD, true)
Patches currently in stable-queue which might be from bristot@xxxxxxxxxx are
queue-5.4/sched-rt-disable-rt_runtime_share-by-default.patch
