emerge broadcom-sta fails (6.1.12 kernel) due to PREEMPT_RCU

[oneone]

Hi!

I've recently built the 6.1.12 kernel, which is now stable for amd64. I am failing, however, to build all of the packages in @modules-rebuild, in particular net-wireless/broadcom-sta-6.30.223.271-r6. Below is the output of "emerge -va1 broadcom-sta". The problem seems to be that PREEMPT_RCU=y in my kernel config and I do not know how to change that. There does not seem to be a setting in "make menuconfig" for that [/quote][/code]and when unsetting it manually, "make menuconfig" resets it again. Any ideas?

[fedeliallalinea]

There is an open bug with a patch for this problem, but after that you should fall in the error

[oneone]

Thanks! I will watch that bug in that case and keep the 5.15.88 kernel for so long.

[ukky]

oneone,

Preemption model is selected in General setup->Preemption Model.
Option PREEMPT_RCU cannot be modified directly.
PREEMPT_RCU is selected automatically when you choose any of these preemption models:

a) Preemptible Kernel (Low-Latency Desktop)
b) Fully Preemptible Kernel (Real-Time) (this might not be available on all CPU architectures)

Also, PREEMPT_RCU is selected automatically when you enable PREEMPT_DYNAMIC in 'General setup'.

[oneone]

Thank you very much, ukky. Unsetting PREEMPT_DYNAMIC did the trick. I'll recompile with that setting. Probably it won't fix the issue due to the mentioned bugs, but in any case I would have to unset it.

EDIT: I could successfully rebuild the kernel with the desired settings, but as expected broadcom-sta still fails to compile for the same reason.

[ukky]

[Hu]

The proposed commands look questionable to me. First you use a prompt that traditionally indicates a non-root user, but you propose that the user build in the kernel source tree, which by default only root can do (and which is discouraged: Building the kernel as root can be harmful). Then you use sudo for the install step, which is unnecessary if you meant for all these steps to be root, and it assumes a working sudo, which is not guaranteed. On my system, those latter commands fail because I do not have sudo:

[ukky]

Hu,

I was under impression that oneone knows how to modify kernel build parameters, how to build and install kernel.
My command sequence was a guideline, just an idea.
How a user builds his/her kernel is a matter of preferences, thus '$ make' is just a hint to rebuild a kernel (as a non-root user).
I totally agree with you that building kernel as a root user is really bad idea. Personally, I build kernel out-of-tree as a non-root user.

[oneone]

As I said, I was able to rebuild the kernel with CONFIG_PREEMPT_DYNAMIC=n, but - as mentioned by fedeliallalinea - this is not the only problem that prevents me from building broadcom-sta. Thank you, however, for letting me know how to switch this setting. I know, it's a bit offtopic, but is there a general method for obtaining something like a dependency tree for kernel settings in order to find out which settings implicitly set/unset others?

[ukky]

oneone,

I never heard of any tool that generates the whole dependency tree for kernel settings.
But if you are interested only in a single kernel parameter, let's say PREEMPT_DYNAMIC, you can:

[oneone]

Strange that there is no such thing - I come across this issue every now and then.

I am aware of the search functionality in menuconfig, but there seem to be two problems. Firstly the "Selects" list is not always exhaustive (e.g. the list for PREEMPT_DYNAMIC does not show that it selects PREEMPT_RCU) and secondly there is not always a "Depends on" list, which I am most interested in (e.g. PREEMPT_RCU does not have such a list, the entry only shows that it selects TREE_RCU).

[ukky]

oneone,

To do a collect full information and find all dependencies for a specific kernel parameter, for example PREEMPT_RCU:

[pietinger]

oneone,

you are right, sometimes its hard to understand kernels logic ... because there have been changes in the past ... PREMPT_RCU is a good example ... Today it is a "calculated" option you cannot change directly. What to do when you have such an option ?

First: Search with / (you have done). You get this information:

[Hu]

For a simple search like this, there is no need to use find, especially with -exec, which creates numerous child processes. You can get an equivalent result, much faster, with:

[oneone]

Ok cool, I found the help text, that's a start (thx pietinger)

I also got the list of files where PREEMPT_RCU occurrs in, but that is only:

[pietinger]

[ukky]

You have to find definition for PREEMPT_DYNAMIC, it will show what other options it selects. In this case it's PREEMPT_BUILD.
Then PREEMPT_BUILD selects PREEMPTION.
And PREEMPTION will select PREEMPT_RCU.

[oneone]

Ooh, I see. I totally missed the "if PREEMPTION" part

Thank you so much!!!

[pietinger]

[pietinger]