kern/94939: [acpi] [patch] reboot(8) fails on IBM / Intel blades

[Devon H. O'Dell]

The following reply was made to PR kern/94939; it has been noted by GNATS.

From: "Devon H. O'Dell" <devon.odell at gmail.com>
To: "Nate Lawson" <nate at root.org>, "John Baldwin" <jhb at freebsd.org>, 
	bug-followup at freebsd.org
Cc:  
Subject: Re: kern/94939: [acpi] [patch] reboot(8) fails on IBM / Intel blades
Date: Thu, 30 Mar 2006 10:31:05 -0800

 >John Baldwin wrote:
 >> On Tuesday 28 March 2006 02:22 pm, Devon H. O'Dell wrote:
 >>> On Tue, Mar 28, 2006 at 11:08:02AM -0800, Nate Lawson wrote:
 >>>> The system must reset immediately following the write to this register=
 .
 >>>> OSPM assumes that the processor will not execute beyond the write
 >>>> instruction. OSPM should execute spin loops on the CPUs in the system
 >>>> following a write to this register.
 >>> My interpretation of this is ``don't do anything else after
 >>> the write to the register, because you can't expect to do
 >>> it.'' Since they say that the system ``must reset immediately
 >>> following the write'', it seems that this is implemented in
 >>> hardware, and we can't assume that we will be able to do
 >>> anything afterwards, anyway.
 >>>
 >>>> So I'm ok with the patch being committed if no other tasks need to
 >>>> happen after this shutdown handler is called.  Also, all APs should be
 >>>> stopped before this happens and it should only occur once on the BSP.
 >>> I was curious if anything happens after this handler is
 >>> called -- if there is, we definitely need to move it back
 >>> to later in the process. Again, I put the code here because it
 >>> looked to me like the procedure already assumed nothing else
 >>> is happening, but it sounds like there are other procedures
 >>> that are in the call queue after this one.
 >>
 >> It really should be much later I think: in cpu_reset_real() as that
 >> is the only place that you know that the APs are stopped.
 >
 > I'm not near a BSD box today.  Is there a simple, MI way of hooking
 > there that doesn't require ACPI compiled into the kernel?  If it's a
 > simple matter of moving it to a different shutdown handler or adding a
 > way for acpi to conditionally override cpu_reset_real, that's ok with
 > me.  I don't want acpi being partially merged into the main kernel.
 
 I can move this to its own event handler that will be executed later on.
 
 > --
 > Nate