linuxkpi: make FPU sections thread-safe and NOCTX

[val_packett.cool]

Summary

FPU_KERN_NOCTX should be enough to match the Linux semantics.

+ add explanation for the nesting counter.

Test Plan

Test with an AMD Navi GPU.

[kib]

sys/compat/linuxkpi/common/include/asm/fpu/api.h

35–36

Comment should follow style.

43

Use ANSI C definitions.

44–45

This is still completely melts if more than one thread does kernel_fpu_begin()

[• hselasky]

sys/compat/linuxkpi/common/include/asm/fpu/api.h

44–45

Feel free to extend the LinuxKPI's "current" with this variable.

[val_packett.cool]

sys/compat/linuxkpi/common/include/asm/fpu/api.h

43

Huh? The only non-ANSI thing I know of is "K&R style" local variables being declared before the opening { bracket. But these functions do not declare any locals at all…??

44–45

Feel free to extend the LinuxKPI's "current" with this variable.

OH! Thanks, that makes sense now. Where was this comment when I posted the original patch ;)

[val_packett.cool]

sys/compat/linuxkpi/common/include/asm/fpu/api.h

43

Oh.. you mean the whole "blank () args doesn't mean no args" thing I guess

[val_packett.cool]

No one is stepping up to test on affected hardware, so I guess this can just be committed already

[• hselasky]

Make sure you bump the __FreeBSD_version when you commit this.

--HPS

[val_packett.cool]

well, I can't exactly commit anything myself ;)

[• hselasky]

I'll try to help you. Just be patient :-)

[vishwin]

This broke at least i915kms from drm-kmod despite building successfully. I've reported there as well, since I'm not sure where any fixes need to go.

[• hselasky]

Should be fixed now.