Re: [PATCH] Booting when CPUs fail to come up.

[Rusty Russell]

In message <20040221133359.GA339@xxxxxxxxxx> you write:
> Hi!
> 
> > > > I recently played with setting a bit in cpu_possible_map that wasn't
> > > > in cpu_online_map: this can happen without hotplug CPU when a CPU
> > > > fails to boot, for example.
> > > 
> > > Is it safe to continue when one cpu is apparently malfunctioning?
> > 
> > Well, patch was overzealous and no longer required.
> > 
> > But we shouldn't crash when this happens just because a CPU didn't
> > come up.
> 
> I still do not agree.

You're entitled.  However, on x86 we booted before when a secondary
CPU didn't come up, and the patch was designed to ensure that we still
did so.

> You have a system you tried to kick CPU #13 alive, and something very
> wrong happened, CPU #13 did not come up. It is there, has full access
> to memory, it is probably running some kind of program....

No, it's possible, but not online.  This actually happens on archs
where you have hotplug cpus, as well as x86 boot failures.

> I'd not dare mount disks read-write in such situation and I believe
> crashing early is actually right thing to do.

Sure, send a patch for x86 to do that, and we can discuss that.  I'm
not going to break existing behavior by stealth though.

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