kernel: Add automation to sort all constructors and destructors at compile time.
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Authored by • hselasky on May 21 2023, 4:16 PM.

Details

Reviewers

imp
kib

Summary

List of changes:

Factor out sorting function for all constructors and destructors.
Use insertion sort instead of bubble sort. Because insertion sort is much faster when the data is already sorted.
Add generic automation layer to sort constructors and destructors at compile time.
Invert subsystem and order values for all destructors to reflect actual order. Because then only one sorting function is needed.

MFC after: 1 week
Sponsored by: NVIDIA Networking

Test Plan

Added some prints and verified no sysinit sorting was done during startup, also when loading modules.

Repository

rG FreeBSD src repository

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• hselasky requested review of this revision.May 21 2023, 4:16 PM

• hselasky created this revision.

I'll have to study this in detail... it's a bigger change than I thought it would be...

sys/kern/init_main.c
241	Won't klds create unsorted entries at the end?

In D40193#915024, @imp wrote:

I'll have to study this in detail... it's a bigger change than I thought it would be...

Right. When there is no compiler support.

The problem with the constructor attribute is when you load KLD's that you need to merge two constructor lists. I didn't spend time on that.

• hselasky marked an inline comment as done.May 21 2023, 5:09 PM

• hselasky added inline comments.

sys/kern/init_main.c
241	The KLDs loaded at boot, also have a sorted init and uninit section after my change. That's why I modified sysinit_add() to merge two sorted lists, instead of just concatenating the lists. When you merge two sorted lists, the resulting list also becomes sorted, and then no further sorting is needed.