Re: WARNING: suspicious RCU usage - sdhci-pltfm: SDHCI platform and OF driver helper

[peterz@infradead.org]

On Tue, Sep 01, 2020 at 02:35:52PM +0200, Ulf Hansson wrote:
> On Tue, 1 Sep 2020 at 12:42, <peterz@infradead.org> wrote:

> > That said; I pushed the rcu_idle_enter() about as deep as it goes into
> > generic code in commit 1098582a0f6c ("sched,idle,rcu: Push rcu_idle
> > deeper into the idle path")
> 
> Aha, that commit should fix this problem, I think. Looks like that
> commit was sent as a fix and included in the recent v5.9-rc3.

AFAICT psci_enter_domain_idle_state() is still buggered. All that
pm_runtime_*() stuff is using locks.

Look at this:

  psci_enter_domain_idle_state()
    pm_runtime_put_sync_suspend()
      __pm_runtime_suspend()
        spin_lock_irqsave(&dev->power.lock, flags);

That's a definite fail after we've done rcu_idle_enter().

> > I suppose the next step is pushing it into individual driver when
> > needed, something like the below perhaps. I realize the coupled idle
> > state stuff is more complicated that most, but it's also not an area
> > I've looked at in detail, so perhaps I've just made a bigger mess, but
> > it ought to give you enough to get going I think.
> 
> These aren't coupled states. Instead, in cpuidle-psci, we are using PM
> domains through genpd and runtime PM to manage "shared idle states"
> between CPUs.

Similar problem I'm thinking, 'complicated' stuff.