Messages in this thread | | | Date | Wed, 8 Feb 2023 10:35:11 +0000 | From | Sudeep Holla <> | Subject | Re: s2idle breaks on machines without cpuidle support |
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On Wed, Feb 08, 2023 at 04:48:18AM +0900, Kazuki wrote: > On Mon, Feb 06, 2023 at 10:12:39AM +0000, Sudeep Holla wrote: > > > > What do you mean by break ? More details on the observation would be helpful. > For example, CLOCK_MONOTONIC doesn't stop even after suspend since > these chain of commands don't get called. > > call_cpuidle_s2idle->cpuidle_enter_s2idle->enter_s2idle_proper->tick_freeze->sched_clock_suspend (Function that pauses CLOCK_MONOTONIC) > > Which in turn causes programs like systemd to crash since it doesn't > expect this.
Yes expected IIUC. The per-cpu timers and counters continue to tick in WFI and hence CLOCK_MONOTONIC can't stop.
> > > > > 2. Suspend actually works on ARM64 machines even without proper > > > cpuidle (PSCI cpuidle) since they support wfi, so the assumption here is wrong > > > on such machines > > > > > > > Sorry I am bit confused here. Your point (2) contradicts the $subject. > drivers/cpuidle/cpuidle.c: > > bool cpuidle_not_available(struct cpuidle_driver *drv, > struct cpuidle_device *dev) > { > return off || !initialized || !drv || !dev || !dev->enabled; > } > > The cpuidle framework reports ARM64 devices without PSCI cpuidle as > "cpuidle not available" even when they support wfi, which causes suspend > to fail, which shouldn't be happening since they do support idling.
Yes with just WFI, there will be no active cpuidle driver.
[...]
> > Again, since s2idle is userspace driven, I don't understand what do you > > mean by unbootable kernel in the context of s2idle. > > Sorry, I meant "attempts to fix this bug have all led to an unbootable > kernel."
Again I assume you mean kernel hang or crash and nothing to do with boot. Once you enter s2i state with your changes/fix, it hangs or is unresponsive as it might have either failed to enter or resume from the state.
-- Regards, Sudeep
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