Centralize __pcpu definitions.

[kib]

Summary

Many extern struct pcpu <something>__pcpu declarations were copied/pasted in sources. The issue is the definition is MD, but it cannot be provided by machine/pcpu.h due to actual struct pcpu defined in sys/pcpu.h later than the inclusion of machine/pcpu.h. There is no way around it, due to machine/pcpu.h supplying part of struct pcpu fields.

To work around the problem, add a new machine/pcpu_aux.h header, which should fill any needed MD definitions after struct pcpu definition is completed. This allows to remove copies of __pcpu spread around the source.

While there, fix bhyve.

[I only handled x86 and riscv, the later was not compiled. I will finish the patch after the discussion]

[imp]

Seems a bit wasteful to have multiple files with the same bits, but since some are arrays and others are pointers, I'm unsure of what to suggest instead.

[jhb]

sys/sys/pcpu.h

175

Maybe it would be simpler if we inverted these macros and had sys/pcpu.h define a PCPU_MI_FIELDS macro before #including <machine/pcpu.h> and then the MD header would define the actual 'struct pcpu' using 'PCPU_MI_FIELDS' as the first line? We could add a static assert that offsetof(struct pcpu, pc_curthread) == 0 in subr_pcpu.c. Would this let us keep a single header?

[kib]

sys/sys/pcpu.h

175

I suspect it would not, because due some definitions in sys/pcpu.h now would require placement after machine/pcpu.h defined complete struct pcpu. cpuhead is the first example.

Also IMO it would cause much larger churn in source.

[kib]

pcpu_aux.h also allows to heal some wounds like OFFSETOF_CURTHREAD and remove clang-specific workarounds, since offsetof() is not literal 0 AKA NULL.

[markj]

It seems reasonable to me.

sys/riscv/include/pcpu_aux.h

47

"... zones, the page size should be a multiple of the size of struct pcpu."

50

This could be written more simply as PAGE_SIZE % sizeof(struct pcpu) == 0.

[kib]

risc-v pcpu_aux.h editing.

[kib]

Complete pass over rest of the arches. This version passes tinderbox.

[lwhsu]

sys/sparc64/include/pcpu_aux.h~

1 ↗

(On Diff #61426)

this file looks accidentally added.

[markj]

There is both sparc64/pcpu_aux.h and sparc64/pcpu_aux.h~ in the diff.

[kib]

Remove emacs' backup.