On Tue, Dec 05, 2006 at 05:06:03PM +0100, Simon Oosthoek wrote:
> >There is a watchdog, but I don't think it monitors CPU usage. (A user
> >process can not refuse to give the CPU back to the Linux kernel.) The
> >watchdog reboots the device when critical system processes die.
>
> From what I've read, it also kills when the CPU is hogged (sorry, can't
> find the source right now, but it was an IRC log)
> the command: ./flasher-2.0 --set-rd-flags=no-lifeguard-reset
> seems to have stopped the crashes, but I'm not sure how safe this is...
AFAIU the lifeguard-reset is a different beast from the watchdog. Also,
according to the list of R&D flags from the flasher usage document[1],
there seem to be two different watchdogs:
no-omap-wd
no-retu-wd
no-lifeguard-reset
[1] http://maemo.org/maemowiki/Flasher_tool_usage
The "Retu" custom ASIC chip includes a watchdog [2]. The OMAP one might
be integral to the CPU. The KernelConfig page [3] lists it under
"USB-based Watchdog Cards"
[2] http://maemo.org/maemowiki/CodeNames
[3] http://maemo.org/maemowiki/KernelConfig
When the lifeguard reboots your device, /proc/bootreason shows sw_rst,
while watchdog resets result in 32_wd [4].
[4] http://maemo.org/maemowiki/ReportingRebootIssues
It would be interesting to know which process is responsible for pinging
the watchdogs, and how often these need to be pinged.
I've noticed that when you write something to the internal flash memory,
the kernel gets a huge interrupt storm and the device starts to act
sluggish, even though the CPU is reported to be idle (source: playing
with self-compiled vmstat). I haven't seen any watchdog resets caused
by this, though.
Marius Gedminas
--
C++ is a loaded machine gun helpfully pointed at your feet with the safety off.
-- ChaosDiscord on Slashdot
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