Messages in this thread | | | Subject | Re: [PATCH v2] reboot: Backup orderly_poweroff | From | Keerthy <> | Date | Tue, 19 Jan 2016 16:02:30 +0530 |
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Hi Ingo,
On Tuesday 19 January 2016 02:36 PM, Ingo Molnar wrote: > > * Grygorii Strashko <grygorii.strashko@ti.com> wrote: > >> On 01/15/2016 12:14 PM, Ingo Molnar wrote: >>> >>> * One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> wrote: >>> >>>>> If kernel_power_off() is called then the system should power off. No ifs and >>>>> whens. >>>> >>>> Even if it doesn't the watchdog should kill it. >>>> >>>> That is broken on some platforms on the watchdog side as the >>>> watchdog shuts down during our power off callbacks - because the system >>>> firmware is too stupid to reset the watchdog as it powers back up (so >>>> keeps rebooting). >>>> >>>> If you watchdog and firmware function properly you shouldn't even have to >>>> care if you crash during the kernel power off. >>> >>> That's a good point as well - if the system is 'stuck' for some notion of stuck, >>> then watchdog drivers can help. >>> >> >> Seems ARM doesn't have endless loop implemented in machine_power_off() - so, >> not too much chances for Watchdog to fire. >> void machine_power_off(void) >> { >> local_irq_disable(); >> smp_send_stop(); >> >> if (pm_power_off) >> pm_power_off(); >> >> --- endless loop ? >> --- or restart ? >> } >> [and even if it will be there - 20-30sec is usual timeout for Watchdog and this >> enough time to burn the system in case of thermal emergency poweroff :(] >> >>> Here it's unclear whether user-space even called the sys_reboot() system call. >>> >> >> That's true - original log [1] has >> Nov 30 11:19:22 [ 5.942769] thermal thermal_zone3: critical temperature reached(108 C),shutting down >> [...] >> Nov 30 11:19:24 [ 7.387900] ahci 4a140000.sata: flags: 64bit ncq sntf stag pm led clo only pmp pio slum part ccc apst >> Nov 30 11:19:24 INIT: Switching to runlevel: 0 >> Nov 30 11:19:24 INIT: Sending processes the TERM signal >> >> and there are no >> [ 220.004522] reboot: Power down >> >> >> Also, It's not the first time this part of code is discussed (thermal emergency poweroff) [2], >> so the good question, as for me, is it really required and safe to use orderly_poweroff() in >> case of thermal emergency poweroff ([3] as example)? >> >> In general, this kind of use case can be simulated using SysRq on any arch >> - [3.290034] Freeing unused kernel memory: 492K (c0a67000 - c0ae2000) >> INIT: version 2.88 booting >> Starting udev >> ^^ The issue most probably might happens when system in the process of loading modules >> So, once modules loading process is started - fire Sysrq "poweroff(o)" > > So I'd say emergency poweroff should be named accordingly - and the > orderly_poweroff() name suggest anything but an emergency, right? > > So I'd be fine with the following: > > - introduce a poweroff_emergency() core kernel function call > > - use it in drivers where it's justified > > - poweroff_emergency() has a configurable timeout value. If the timeout value is > set to 0 then it powers the system off immediately. > > Functionally it would be mostly equivalent to your current patch (except the '0' > immediate poweroff functionality).
Thanks for the suggestion. I will work on this and get back.
Best Regards, Keerthy
> > Thanks, > > Ingo >
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