Hi Christian,
Le 26/02/2026 à 06:37, Christian Zigotzky a écrit :
On 25/02/26 08:16, Christophe Leroy (CS GROUP) wrote:
+Peter
Hi Christian,
Le 25/02/2026 à 06:54, Christian Zigotzky a écrit :
Hello,
We were previously able to disable PREEMPT in the kernel
configuration, but the latest kernels now enable it by default and it
is no longer possible to disable it.
Is it possible to let us decide whether to activate PREEMPT or not?
Can you give more details on why you want to be able to deactivate
PREEMPT ?
Read https://eur01.safelinks.protection.outlook.com/?
url=https%3A%2F%2Fgithub.com%2Ftorvalds%2Flinux%2Fcommit%2F7dadeaa6e851e&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C7006c8b4b98c4315a7e508de74f9388a%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639076810956939768%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=6xLB%2FOVSkmgZRamaBM9zaxm%2FUTk9ssf4409QJdiXkDg%3D&reserved=0
I use PREEMPT_NONE kernels on my Linux PPC servers. (Without desktop)
You are doing that today because it is possible. Tomorrow it will not be
possible anymore, for the reasons explained by Peter.
My question was not to know what you are doing but why, and why you
think you still need PREEMPT_NONE and why the modern PREEMPT_LAZY is not
good enough for you.
Christophe
Currently we use the following revert patch for our non-preempt kernels.
--- a/kernel/Kconfig.preempt 2026-02-14 10:06:32.000000000 +0000
+++ b/kernel/Kconfig.preempt 2026-02-08 21:03:27.000000000 +0000
@@ -16,13 +16,11 @@ config ARCH_HAS_PREEMPT_LAZY
choice
prompt "Preemption Model"
- default PREEMPT_LAZY if ARCH_HAS_PREEMPT_LAZY
default PREEMPT_NONE
config PREEMPT_NONE
bool "No Forced Preemption (Server)"
depends on !PREEMPT_RT
- depends on ARCH_NO_PREEMPT
select PREEMPT_NONE_BUILD if !PREEMPT_DYNAMIC
help
This is the traditional Linux preemption model, geared towards
@@ -37,7 +35,6 @@ config PREEMPT_NONE
config PREEMPT_VOLUNTARY
bool "Voluntary Kernel Preemption (Desktop)"
- depends on !ARCH_HAS_PREEMPT_LAZY
depends on !ARCH_NO_PREEMPT
depends on !PREEMPT_RT
select PREEMPT_VOLUNTARY_BUILD if !PREEMPT_DYNAMIC
---
Thanks in advance,
Christian
