Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Tue, 12 Feb 2019 00:05:07 +0100 | Subject | Re: [PATCH 1/2] PM-runtime: Take suppliers into account in __pm_runtime_set_status() |
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On Mon, Feb 11, 2019 at 4:51 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > On Mon, 11 Feb 2019 at 14:27, Ulf Hansson <ulf.hansson@linaro.org> wrote: > > > > On Thu, 7 Feb 2019 at 19:46, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > > > > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > > > If the target device has any suppliers, as reflected by device links > > > to them, __pm_runtime_set_status() does not take them into account, > > > which is not consistent with the other parts of the PM-runtime > > > framework and may lead to programming mistakes. > > > > > > Modify __pm_runtime_set_status() to take suppliers into account by > > > activating them upfront if the new status is RPM_ACTIVE and > > > deactivating them on exit if the new status is RPM_SUSPENDED. > > > > > > If the activation of one of the suppliers fails, the new status > > > will be RPM_SUSPENDED and the (remaining) suppliers will be > > > deactivated on exit (the child count of the device's parent > > > will be dropped too then). > > > > > > Of course, adding device links locking to __pm_runtime_set_status() > > > means that it cannot be run fron interrupt context, so make it use > > > spin_lock_irq() and spin_unlock_irq() instead of spin_lock_irqsave() > > > and spin_unlock_irqrestore(), respectively. > > > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > Rafael, thanks for working on this! > > > > I am running some tests at my side, but still not achieving the > > behavior I expect to. Will let you know when I have more details, but > > first some comments below. > > Alright, this is what I found. > > When I call pm_runtime_set_suspended(), in the ->probe() error path of > my RPM test driver (I am removing the device link afterwards), then my > expectation was that this should allow the supplier to become runtime > suspended (sooner or later). This isn't the case, as it turns out the > runtime PM usage count of the supplier, still remains 1 after the > probe failure. > > My observation is that with $subject patch, the link->rpm_active count > is now reaching 1, before it stayed at 2 - so one step forward. :-) > > However, the reason to why the runtime PM usage count never reaches 0, > is because of the call to pm_runtime_get_noresume(supplier) in > device_link_rpm_prepare(), which is called from device_link_add().
That was there previously, I've just moved it to device_link_rpm_prepare().
But good catch!
> To solve the problem, it seems like we need to call > pm_runtime_put(supplier), in case the device link is deleted while the > consumer is still probing.
I'd rather change the way pm_runtime_get/put_suppliers() work, so that they use the rpm_active refcount, but pm_runtime_put_suppliers() only drops it by one - unless it is one already.
Then, when adding a new link with DL_FLAG_RPM_ACTIVE, device_link_add() only needs to increment its rpm_active *twice* (instead of doing that once as to does now), so it will stay above one after the subsequent pm_runtime_put_suppliers() - and if it goes away in the meantime, then it will be cleaned up by the removal.
In turn, if a link is created without DL_FLAG_RPM_ACTIVE, its rpm_active is one and then pm_runtime_put_suppliers() will just skip it.
A patch will follow. :-)
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