Re: [PATCH 1/11] Add generic helpers for arch IPI function calls

[Mark Lord]

Jens Axboe wrote:
> On Wed, Apr 23 2008, Mark Lord wrote:
> ..
> > The second bug, is that for the halt case at least,
> > nobody waits for the other CPU to actually halt
> > before continuing.. so we sometimes enter the shutdown
> > code while other CPUs are still active.
> >
> > This causes some machines to hang at shutdown,
> > unless CPU_HOTPLUG is configured and takes them offline
> > before we get here.
>
> I'm guessing there's a reason it doesn't pass '1' as the last argument,
> because that would fix that issue?
..

Undoubtedly -- perhaps the called CPU halts, and therefore cannot reply.  :)

But some kind of pre-halt ack, perhaps plus a short delay by the caller
after receipt of the ack, would probably suffice to kill that bug.

But I really haven't studied this code enough to know,
other than that it historically has been a sticky area
to poke around in.

Cheers


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/