Real-time kerel not detected on patched 6.12

royka wrote:

For Raspberry I think following this guide should help: github.com/by/RT-Kernel

Only after git clone, download this patch:
forum.linuxcnc.org/media/kunena/attachme...ernel-realtime.patch
Then enter the Linux folder and enter: git apply ../sys-kernel-realtime.patch
After make menuconfig make sure that these are also selected:
forum.linuxcnc.org/38-general-linuxcnc-q...6-12?start=10#315643

This does not work in all build environments. I think Cornholio is correct

royka wrote:

Like you assumed before I think those patches indeed didn't make it to the mainline kernel, but those are not needed to make a fully preemptible kernel.

The sysfs patch is only needed because LinuxCNC checks that indicator. Later I saw that the source of Raspberry also already has the arch_supports_rt in the kconfig.
 

Whilst it does have that it's not the correct value.....from the required patch I've used with 6.1.69 

Yes but we were talking about 6.12 and up, of course for 6.1.x you still need patches.

And for 6.12 the patches from kernel.org are still required, other wise you can only select a low-latency desktop, not a fully_preemptible model, which would appear to be "a proper realtime kernel" suitable for a RTOS.

I've work through the image builder for 6.12.y, and I can say from configuring the kernel, that the patches from kernel.org are required. Depending on the commit you chose in the 6.12.y branch there may not be a matching patchset.

So it's not just a case of choosing the 6.12.y branch but also the commit that matches a patchset that is available.

Image below shows a kernel from the 6.12.y branch, commit 236f36133619216a5c8faea1a8c2c93c83efc2f4, which is kernel 6.12.8. This is has been patched with those from kernel.org and a patch, required for the build process to succeed, from Rods repo. As you can see there is an option to select the full preemptible kernel. Without the patch this does not appear. Yes while the sysfs patch does add the ability to report to Linuxcnc the kernel is "realtime" the kernel is only a low-latency-desktop.
As I type I'm running an image build on another machine.
 
 

I don't know what you do wrong, but this is without any patch or modification:
 

It seems that this user also didn't need additional patches: forum.linuxcnc.org/38-general-linuxcnc-q...6-12?start=10#318472

Sorry, I have not had a chance to look at this over the weekend.

I don't what your doing different but using the rpi-linux source from their github repo, I cloned the whole repo, I'm getting this, unpatched sources.
Just out of interest are you working from the same kernel source as myself.

Another thing of interest there are still patches.
Directory listing of the patches that are for 6.12.8 none for 6.12.9 as you can see (6.12.8) has patches for sysfs entry and one to for enable arm rt.

So this looks like a very confusing kettle of fish.

-rw-rw-r-- 1 rmurphy rmurphy 1495 Jan 9 22:27 0001-arm-Disable-jump-label-on-PREEMPT_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 2447 Jan 9 22:27 0001-ARM-vfp-Provide-vfp_state_hold-for-VFP-locking.patch
-rw-rw-r-- 1 rmurphy rmurphy 3888 Jan 9 22:27 0001-drm-i915-Use-preempt_disable-enable_rt-where-recomme.patch
-rw-rw-r-- 1 rmurphy rmurphy 1382 Jan 9 22:27 0001-hrtimer-Use-__raise_softirq_irqoff-to-raise-the-soft.patch
-rw-rw-r-- 1 rmurphy rmurphy 3902 Jan 9 22:27 0001-powerpc-Add-preempt-lazy-support.patch
-rw-rw-r-- 1 rmurphy rmurphy 6700 Jan 9 22:27 0001-sched-Add-TIF_NEED_RESCHED_LAZY-infrastructure.patch
-rw-rw-r-- 1 rmurphy rmurphy 1384 Jan 9 22:27 0002-ARM-vfp-Use-vfp_state_hold-in-vfp_sync_hwstate.patch
-rw-rw-r-- 1 rmurphy rmurphy 3671 Jan 9 22:27 0002-drm-i915-Don-t-disable-interrupts-on-PREEMPT_RT-duri.patch
-rw-rw-r-- 1 rmurphy rmurphy 1511 Jan 9 22:27 0002-locking-rt-Remove-one-__cond_lock-in-RT-s-spin_trylo.patch
-rw-rw-r-- 1 rmurphy rmurphy 1286 Jan 9 22:27 0002-powerpc-Large-user-copy-aware-of-full-rt-lazy-preemp.patch
-rw-rw-r-- 1 rmurphy rmurphy 11004 Jan 9 22:27 0002-sched-Add-Lazy-preemption-model.patch
-rw-rw-r-- 1 rmurphy rmurphy 970 Jan 9 22:27 0002-timers-Use-__raise_softirq_irqoff-to-raise-the-softi.patch
-rw-rw-r-- 1 rmurphy rmurphy 3282 Jan 9 22:27 0002-tracing-Record-task-flag-NEED_RESCHED_LAZY.patch
-rw-rw-r-- 1 rmurphy rmurphy 1404 Jan 9 22:27 0003-ARM-vfp-Use-vfp_state_hold-in-vfp_support_entry.patch
-rw-rw-r-- 1 rmurphy rmurphy 1741 Jan 9 22:27 0003-drm-i915-Don-t-check-for-atomic-context-on-PREEMPT_R.patch
-rw-rw-r-- 1 rmurphy rmurphy 2853 Jan 9 22:27 0003-locking-rt-Add-sparse-annotation-for-RCU.patch
-rw-rw-r-- 1 rmurphy rmurphy 2660 Jan 9 22:27 0003-riscv-add-PREEMPT_LAZY-support.patch
-rw-rw-r-- 1 rmurphy rmurphy 3721 Jan 9 22:27 0003-sched-Enable-PREEMPT_DYNAMIC-for-PREEMPT_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 7638 Jan 9 22:27 0003-softirq-Use-a-dedicated-thread-for-timer-wakeups-on-.patch
-rw-rw-r-- 1 rmurphy rmurphy 3696 Jan 9 22:27 0004-ARM-vfp-Move-sending-signals-outside-of-vfp_state_ho.patch
-rw-rw-r-- 1 rmurphy rmurphy 2170 Jan 9 22:27 0004-drm-i915-Disable-tracing-points-on-PREEMPT_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 1319 Jan 9 22:27 0004-locking-rt-Annotate-unlock-followed-by-lock-for-spar.patch
-rw-rw-r-- 1 rmurphy rmurphy 2089 Jan 9 22:27 0004-sched-x86-Enable-Lazy-preemption.patch
-rw-rw-r-- 1 rmurphy rmurphy 3199 Jan 9 22:27 0005-drm-i915-gt-Use-spin_lock_irq-instead-of-local_irq_d.patch
-rw-rw-r-- 1 rmurphy rmurphy 8921 Jan 9 22:27 0005-sched-Add-laziest-preempt-model.patch
-rw-rw-r-- 1 rmurphy rmurphy 1305 Jan 9 22:27 0006-drm-i915-Drop-the-irqs_disabled-check.patch
-rw-rw-r-- 1 rmurphy rmurphy 1151 Jan 9 22:27 0007-drm-i915-guc-Consider-also-RCU-depth-in-busy-loop.patch
-rw-rw-r-- 1 rmurphy rmurphy 762 Jan 9 22:27 0008-Revert-drm-i915-Depend-on-PREEMPT_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 10272 Jan 9 22:27 0053-serial-8250-Switch-to-nbcon-console.patch
-rw-rw-r-- 1 rmurphy rmurphy 942 Jan 9 22:27 0054-serial-8250-Revert-drop-lockdep-annotation-from-seri.patch
-rw-rw-r-- 1 rmurphy rmurphy 379 Jan 9 22:27 Add_localversion_for_-RT_release.patch
-rw-rw-r-- 1 rmurphy rmurphy 1013 Jan 9 22:27 ARM__Allow_to_enable_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 1370 Jan 9 22:27 arm-Disable-FAST_GUP-on-PREEMPT_RT-if-HIGHPTE-is-als.patch
-rw-rw-r-- 1 rmurphy rmurphy 3310 Jan 9 22:27 ARM__enable_irq_in_translation_section_permission_fault_handlers.patch
-rw-rw-r-- 1 rmurphy rmurphy 7625 Jan 9 22:27 netfilter-nft_counter-Use-u64_stats_t-for-statistic.patch
-rw-rw-r-- 1 rmurphy rmurphy 1061 Jan 9 22:27 POWERPC__Allow_to_enable_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 1837 Jan 9 22:27 powerpc_kvm__Disable_in-kernel_MPIC_emulation_for_PREEMPT_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 3446 Jan 9 22:27 powerpc_pseries_iommu__Use_a_locallock_instead_local_irq_save.patch
-rw-rw-r-- 1 rmurphy rmurphy 903 Jan 9 22:27 powerpc-pseries-Select-the-generic-memory-allocator.patch
-rw-rw-r-- 1 rmurphy rmurphy 1120 Jan 9 22:27 powerpc_stackprotector__work_around_stack-guard_init_from_atomic.patch
-rw-rw-r-- 1 rmurphy rmurphy 1249 Jan 9 22:27 powerpc__traps__Use_PREEMPT_RT.patch
-rw-rw-r-- 1 rmurphy rmurphy 1762 Jan 9 22:27 riscv-add-PREEMPT_AUTO-support.patch
-rw-rw-r-- 1 rmurphy rmurphy 930 Jan 9 22:27 sched-Fixup-the-IS_ENABLED-check-for-PREEMPT_LAZY.patch
-rw-rw-r-- 1 rmurphy rmurphy 4049 Jan 9 22:27 series
-rw-rw-r-- 1 rmurphy rmurphy 1401 Jan 9 22:27 sysfs__Add__sys_kernel_realtime_entry.patch
-rw-rw-r-- 1 rmurphy rmurphy 2965 Jan 9 22:27 tracing-Remove-TRACE_FLAG_IRQS_NOSUPPORT.patch

rodw wrote:

Sorry, I have not had a chance to look at this over the weekend.
 

Yeah I figured that cos building an image with the 6.12.y branch fails when creating the final image. 6.1.y with the 6.1.69 kernel commit seems to build ok, image is created with Linuxcnc binaries and when patch has spi on at first boot. This was just seen by mounting the image and having a quick browse through the filesystem. Too effing late to test.

These are the exact commands I do:
git clone github.com/raspberrypi/linux.git -b rpi-6.12.y
cd linux
KERNEL=kernel_2712 make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- bcm2712_defconfig
KERNEL=kernel_2712 make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- menuconfig

After that you choose fully preemptible.
Now I wonder what you do different I guess you didn't use the defconfig, then you should set EXPERT=y like I mentioned before: General Setup => Configure standard kernel features (expert users) and press Y, and Fully Preemptible is visible. But I advise to apply the changes to the defconfig at github.com/by/RT-Kernel except the rtc and ntp options, and use the defconfig.

To enable the realtime indicator I used the patch that I posted on page 2.
wget forum.linuxcnc.org/media/kunena/attachme...ernel-realtime.patch
cd linux
git apply ../sys-kernel-realtime.patch

And to prevent compile errors (after the above patch) go at menuconfig to: General Setup =>  Kexec and crash features => press Y so CRASH_DUMP gets selected so VMCORE_INFO gets selected.