New v. v. experimental HOTPLUG CPU megapatch.

Rusty Russell
2004-02-03T07:43:21Z

[-- Attachment #1: Type: text/plain, Size: 1470 bytes --]

This is my first cut of a patch, still has some old code in it. As an
attachment since it's 70k (I'll split into multiple parts later, this
is the x86 part, too).

Patch against 2.6.2-rc2-mm2. Works basically, gives "APIC error on
CPU1: 08(08)" under stress. Clues welcome.

Basically consists of:

1) New file stop_machine.[ch] which takes logic out of module.c (I
haven't converted module.c code over yet though).

2) x86: arch_cpu_down_check (called before offlining) and arch_cpu_down
(called when machine stopped, moves irqs).

3) x86: idle loop code to play dead.

4) migrate_all_tasks() called with machine stopped, and migrates
kernel threads as well.

5) cpu.c fires off a thread to do the dirty work: it schedules with
interrupts still disabled on dead cpu.

6) Most threads are happy to run on "wrong" CPUs, but slab.c reap
timer needs a little fixing, and still needs to stop when CPU goes
offline. softirq threads are tied to CPU: I just hacked in a check
so the do nothing if CPU is offline. Moving the migration thread
is safe since it should have nothing to do.

7) Ugly change to finish_arch_switch so it doesn't re-enable
interrupts if the CPU is down (switching from take_cpu_down kthread
to idle task). __migrate_task() still needs check for cpu down,
AFAICT.

Given it was about a day's work, I'm happy it works at all...

Cheers,
Rusty.
--
Anyone who quotes me in their sig is an idiot. -- Rusty Russell.

[-- Attachment #2: hotcpu-atomic-test.patch.bz2 --]
[-- Type: application/octet-stream, Size: 17121 bytes --]