Date: Thu, 30 Mar 2006 13:10:10 GMT From: John Baldwin <jhb@freebsd.org> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/94939: [acpi] [patch] reboot(8) fails on IBM / Intel blades Message-ID: <200603301310.k2UDAAKi065594@freefall.freebsd.org>
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The following reply was made to PR kern/94939; it has been noted by GNATS. From: John Baldwin <jhb@freebsd.org> To: "Devon H. O'Dell" <dodell@ixsystems.com> Cc: Nate Lawson <nate@root.org>, bug-followup@freebsd.org Subject: Re: kern/94939: [acpi] [patch] reboot(8) fails on IBM / Intel blades Date: Thu, 30 Mar 2006 08:03:23 -0500 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: > > John Baldwin wrote: > > > Nate, > > > > > > I'm curious where you think this code should go if not here? I'd > > > imagine we don't want to do this after AcpiTerminate() since perhaps > > > the specified register may no longer be available (I might be wrong > > > though, I haven't checked the spec). > > > > I don't have a specific idea since I didn't look at it closely. I think > > there might be some requirements of writes to the reset register > > (delays, expectation of chipset configuration, order with other shutdown > > tasks). Here are the requirements from the spec: > > > > > > 4.7.3.6 Reset Register > > The optional ACPI reset mechanism specifies a standard mechanism that > > provides a complete system reset. When implemented, this mechanism must > > reset the entire system. This includes processors, core logic, all > > buses, and all peripherals. From an OSPM perspective, asserting the > > reset mechanism is the logical equivalent to power cycling the machine. > > Upon gaining control after a reset, OSPM will perform actions in > > like manner to a cold boot. > > ... > > 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. =2D-=20 John Baldwin <jhb@FreeBSD.org> =A0<>< =A0http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" =A0=3D =A0http://www.FreeBSD.org
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