On 12/31/2015 11:29 AM, Eduardo Valentin wrote:
> can we have a shorter title?
>
> On Tue, Dec 29, 2015 at 02:46:49PM +0530, Keerthy wrote:
>> Hi Nishanth,
>>
>
> <cut>
>>>
>>> I am not sure if this #ifdeffery is even needed.
>>>
>>>
>>> Eduardo, Rui: If this is not the suggested technique, maybe you guys
>>> could suggest how we could handle a case where userspace might be
>>> hungup due to some reason and a case where a critical temperature
>>> event in the middle of device probe was triggered?
>
> Orderly power off is supposed to take care of this. Looking at the code,
> it will force a shutdown in case execution of userland command fails:
>
> static int __orderly_poweroff(bool force)
> {
> int ret;
>
> ret = run_cmd(poweroff_cmd);
>
> if (ret && force) {
> pr_warn("Failed to start orderly shutdown: forcing the issue\n");
>
> /*
> * I guess this should try to kick off some daemon to sync and
> * poweroff asap. Or not even bother syncing if we're doing an
> * emergency shutdown?
> */
> emergency_sync();
> kernel_power_off();
> }
Yes, it will *IF* userspace fails. the condition that I had tracked
was before identifying the following fix[1] - Example fail is here[2]
In this case, tmp102 is setup for X15 as [3] - and built as a module.
as the kernel startsup filesystem and starts a modprobe of all modules
via udev rules, the probe of tmp102 detects (falsely) a critical
temperature condition. Shutdown attempt in the middle of driver probe
is always a tricky business.
As we look at the log in [2], Line 472
> thermal thermal_zone3: critical temperature reached(108 C),shutting down
We have userspace trigger for shutdown taking place.
Line 495: INIT: Sending processes the TERM signal
userspace starts shutting down services. (but note that probe for
other devices were either in progress or queued up to complete)..
at line 647 - we are in a weird place -> sysrq shows that system is
idled and userspace is shutdown and system is still active.
In this case, we entered the case thanks to a driver bug, but if this
situation was a real world temperature scenario, then we'd probably in
an overtemp scenario, then device damage could take place OR something
much worse.
The only alternative is to run a parallel thread in case userspace
fails to complete the job in some given period of time - due to what
ever be the condition triggering the problem.
I hope this explains the problem.
[1]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=00917b5c55aeb01322d5ab51af8c025b82959224
[2] http://pastebin.ubuntu.com/14326688/
[3]
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/am57xx-beagle-x15.dts#n738
--
Regards,
Nishanth Menon
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