Re: CPU hotplug broken with 2GB VMSPLIT

[Nathan Lynch <ntl@pobox.com>]

Nathan Lynch wrote:
> Jens Axboe wrote:
> > On Thu, Nov 30 2006, Jens Axboe wrote:
> > > Hi,
> > > 
> > > Just got a new notebook (Lenovo X60), setup a custom kernel and then I
> > > noticed that suspend to ram doesn't work anymore. The machine suspends
> > > just fine, on resume it brings back the text display but reboots after
> > > it has stalled for a few seconds. On the suggestion of Pavel, I tried
> > > testing CPU hotplug, and indeed he was right: I can offline 1 of the
> > > cores fine, bringing it back online freezes the machine for 3-4 seconds
> > > and then reboots.
> > > 
> > > carl:/sys/devices/system/cpu/cpu1 # echo 0 > online 
> > > carl:/sys/devices/system/cpu/cpu1 # dmesg
> > > Breaking affinity for irq 219
> > > CPU 1 is now offline
> > > SMP alternatives: switching to UP code
> > > carl:/sys/devices/system/cpu/cpu1 # echo 1 > online 
> > > Read from remote host carl: Connection reset by peer
> > > 
> > > Booting with maxcpus=1 and resume works fine. Does this ring a bell with
> > > anyone? With highmem enabled and the standard vmsplit, cpu hotplug works
> > > fine for me.
> > 
> > Some more clues - booting with noreplacement doesn't fix it, so I think
> > the alternatives code is off the hook.
> 
> I don't think this adds any new information, but it has been open
> awhile:
> 
> http://bugme.osdl.org/show_bug.cgi?id=6542
> 
> I was able to narrow it down to the vmsplit setting but I wasn't able
> to debug it further.

Hmm, I'm pretty sure this is the same problem I reported in March,
there might be some more information in that thread:

http://marc.theaimsgroup.com/?t=114039363100002&r=1&w=1

but I didn't realize it was vmsplit-related at that time.