Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Mon, 13 Nov 2017 22:58:59 +0100 | Subject | Re: [PATCH] PM / runtime: Drop children check from __pm_runtime_set_status() |
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On Mon, Nov 13, 2017 at 10:50 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > On Monday, November 13, 2017 2:26:28 PM CET Ulf Hansson wrote: >> On 12 November 2017 at 01:27, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: >> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> >> > >> > The check for "active" children in __pm_runtime_set_status(), when >> > trying to set the parent device status to "suspended", doesn't >> > really make sense, because in fact it is not invalid to set the >> > status of a device with runtime PM disabled to "suspended" in any >> > case. It is invalid to enable runtime PM for a device with its >> > status set to "suspended" while its child_count reference counter >> > is nonzero, but the check in __pm_runtime_set_status() doesn't >> > really cover that situation. >> >> The reason to why I changed this in commit a8636c89648a ("PM / >> Runtime: Don't allow to suspend a device with an active child") was >> because to get a consistent behavior. > > Well, it causes the function to return an error in a non-error situation, > which IMnsHO is a bug. > >> Because, setting the device's status to active (RPM_ACTIVE) via >> __pm_runtime_set_status(), requires its parent to also be active (in >> case the parent has runtime PM enabled). > > No!!! > > The check is in there, because the parent's usage_count is affected by that
Actually, the parent's child_count is affected, but that doesn't matter here.
> code and incrementing it in case the parent has runtime PM enabled and is > RPM_SUSPENDED leads to an inconsistent runtime PM state of the parent. IOW, > it would confuse the framework. > > There's no such issue if the runtime PM status of a child is set to RPM_SUSPENDED. > > It is all consistent without the check I'm removing and is made inconsistent > by that very check. > >> I would prefer to try maintain this consistency, but I also I realize >> that commit a8636c89648a, should also have been checking if the parent >> has runtime PM enabled (again for consistency), which it doesn't. >> >> What about fixing that instead? > > Runtime PM is *disabled* for the parent at this point, guaranteed, so there's > nothing to check, I'm afraid ... > > OTOH, the runtime PM status of the children doesn't matter here, because their > reference counters are not updated.
Thanks, Rafael
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