On XO-1.5 with 11.3.0/11.3.1 -- hang during shutdown?

Sridhar Dhanapalan sridhar at laptop.org.au
Mon Jul 16 19:57:50 EDT 2012

Deepak is in India. I have also been able to replicate the problem
using XOs manufactured in the same week (SN SHC037xxxxx). It's
probably easiest if I send my SD cards to James.

James, I'll contact you separately about this.


On 14 July 2012 03:32, Martin Langhoff <martin at laptop.org> wrote:
> Hi folks,
> where is Deepak Muddhaa based? Any reason his failing XO and SD card
> can't be traded for good ones, and the failing units shipped to James,
> Miami or Boston, where we can look at things at a lower level?
> We'll gladly provide a replacement unit.
> I appreciate all the analysis, but it' is apparent that it is being
> done on rather poor data. Hands-on debugging wins.
> cheers,
> m
> On Sun, Jun 24, 2012 at 11:32 PM, James Cameron <quozl at laptop.org> wrote:
>> Thanks for your reply!
>> On Mon, Jun 25, 2012 at 11:16:26AM +1000, Sridhar Dhanapalan wrote:
>>> On 21 June 2012 16:14, James Cameron <quozl at laptop.org> wrote:
>>> > On Thu, Jun 21, 2012 at 02:37:35PM +1000, Sridhar Dhanapalan wrote:
>>> >> On 16 June 2012 17:08, James Cameron <quozl at laptop.org> wrote:
>>> >> > That means the hang should not exceed 15 seconds. ?Is this what you
>>> >> > find? ?If not, then this casts doubt on your solution.
>>> >>
>>> >> I'm going to propose something extremely hackish: [...]
>>> >
>>> > Just to remind you that I'm still interested to know if the hang you
>>> > observe exceeds 15 seconds or not. ?I've not had the time to reproduce
>>> > this hang yet. ?Building a mental model of the problem is important to
>>> > me, because I can sometimes resolve a problem if I have a good model.
>>> Yes; we have left it for several minutes and no shutdown has
>>> occurred.
>> Ooh, I'm surprised.
>> This observation, and the statistical results from your temporary
>> solution (a delay), implies a combination effect, of both the
>> processes not yet terminated, and the umount, leading to a process
>> hang of umount.
>> I can't think of a hack that would meet the requirements:
>> - survive the process deletion steps, and
>> - detect the stalled umount process.
>> I guess you might try remounting the filesystem -o sync, just to
>> further shift the timing.
>> The problem needs a kernel developer to reproduce it.
>> Do you have a way to encourage the problem to occur?  If it can be
>> made to occur on a higher percentage of shutdowns, it becomes easier
>> to debug.  For instance, there is a two second delay in the code, so
>> does the hang occur more frequently if this is reduced to zero?
>>> > The XO-1.75 CPU has a hardware watchdog that could be used for this,
>>> > but you aren't likely to ever have a heat problem with XO-1.75.
>>> That is interesting. Why is that?
>> I take it you mean why won't you have a heat problem with XO-1.75.
>> There are two new characteristics of the XO-1.75 over the XO-1.5:
>> 1.  the maximum power draw of the XO-1.75 at full utilisation is a
>> long way below that of the XO-1.5.  In a scenario where the laptop is
>> powered on and insulated from cooling air flow, this means:
>> 1.a. the temperature rise toward equilibrium will be slower,
>> 1.b. the equilibrium temperature will be lower for a given level of
>> insulation, (stacking, or cloth covers, or both),
>> 1.c. the insulation will have to be far greater to achieve the same
>> equilibrium temperature.
>> 2.  the XO-1.75 has a thermal protection feature that forces the power
>> off if the temperature of the CPU exceeds 85 degrees C, rather than
>> slowing or stopping the CPU as on XO-1.5.  In a scenario where the
>> laptop is powered on and insulated from cooling air flow, this means:
>> 2.a. the temperature rise will be interrupted by a sudden loss of
>> input heat, rather than be slowed by a gradual loss of input heat,
>> 2.b. the insulation will have to be far far greater to achieve the
>> same equilibrium temperature.
>> In this scenario, the heat spreader has very little bearing on the
>> matter.  The heat spreader relies on cooling air flow to the top of
>> the case.  If there is no air flow, the heat spreader is ineffective.
>> The new thermal protection feature isn't a perfect protection; the
>> battery charge circuit remains powered.  So a laptop held between very
>> good insulation (e.g. thick polystyrene with sealed edges) with a flat
>> battery will still heat up, but not nearly as much as one with an
>> active CPU.
>> (Please, test this yourselves with an IR thermometer.  If you don't
>> have one, the closest in Sydney to you would be at the Jaycar store
>> at 127 York St.)
>> --
>> James Cameron
>> http://quozl.linux.org.au/
> --
>  martin at laptop.org -- Software Architect - OLPC
>  - ask interesting questions
>  - don't get distracted with shiny stuff  - working code first
>  - http://wiki.laptop.org/go/User:Martinlanghoff

More information about the Devel mailing list