Re: [Linux PPC] Disable PREEMPT
From: Shrikanth Hegde <sshegde@linux.ibm.com>
Date: 2026-02-25 06:23:35
Hi Christian. Is this sent as a patch or just a reply to the thread? If it is sent as patch, Please follow these guidelines. https://docs.kernel.org/process/submitting-patches.html On 2/25/26 11:24 AM, Christian Zigotzky wrote:
quoted hunk ↗ jump to hunk
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? 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
I would instead fix any issue we have in PREEMPT FULL/LAZY rather than falling back to old methods. btw, did the previous patch sent, which you said helps you to boot, can you confirm it did help you? If yes, i can send it as patch, since cond_resched if called from boot cpu might be stuck in the loop forever. IIRC, after boot, you had some driver causing crash. If so, share backtrace of the crash? If you don't use that driver, is the guest stable?