From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jesse Barnes Date: Wed, 16 Jun 2004 20:40:20 +0000 Subject: Re: [PATCH] early console registration Message-Id: <200406161640.20838.jbarnes@engr.sgi.com> List-Id: References: <200405141425.59867.jbarnes@engr.sgi.com> In-Reply-To: <200405141425.59867.jbarnes@engr.sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Wednesday, June 16, 2004 4:22 pm, Bjorn Helgaas wrote: > On Tuesday 15 June 2004 7:12 am, Jesse Barnes wrote: > > Yeah, that's fine. In fact, I've tested something similar and sent it to > > Andrew, but he came back and asked why not just set CPU 0 online early? > > And given that CPU 0 is 'online' as soon as the kernel starts executing > > head.S, it seems like it *should* keep working, and we should probably > > keep it that way. > > It's *not* online as soon as it starts head.S, though -- that's what I > meant about preserving the original cpu_online semantics. It currently > means that at least cpu_init() has been called, so memory allocation, > per-cpu data, and interrupts should work. Well, online in the sense that it can execute instructions, but yes, other limitations apply, I tried to spell them out in the comments for the function. > If we mark CPU 0 as 'online' earlier, some hypothetical new code could > test cpu_online(0) and incorrectly assume per-cpu data works. Yeah, that's possible, but the window is pretty small. > But AFAIK, there is no such code now, and I don't have any better ideas, > so maybe we should just go with your ia64-specific patch for now. Sounds good to me. Jesse