Date: Thu, 30 Nov 2006 10:43:47 -0600
From: Nathan Lynch <ntl@pobox.com>
To: Jens Axboe <jens.axboe@oracle.com>
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org, pavel@ucw.cz, bryce@osdl.org
Subject: Re: CPU hotplug broken with 2GB VMSPLIT
Message-ID: <20061130164347.GB22050@localdomain>
References: <20061130090348.GK5400@kernel.dk> <20061130091334.GM5400@kernel.dk>
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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.

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