Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Tue, 12 Feb 2019 23:08:50 +0100 | Subject | Re: [PATCH 2/2] driver core: Fix possible supplier PM-usage counter imbalance |
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On Tue, Feb 12, 2019 at 10:03 PM Ulf Hansson <ulf.hansson@linaro.org> wrote: > > On Tue, 12 Feb 2019 at 13:10, Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > If a stateless device link to a certain supplier with > > DL_FLAG_PM_RUNTIME set in the flags is added and then removed by the > > consumer driver's probe callback, the supplier's PM-runtime usage > > counter will be nonzero after that which effectively causes the > > supplier to remain "always on" going forward. > > > > Namely, device_link_add() called to add the link invokes > > device_link_rpm_prepare() which notices that the consumer driver is > > probing, so it increments the supplier's PM-runtime usage counter > > with the assumption that the link will stay around until > > pm_runtime_put_suppliers() is called by driver_probe_device(), > > but if the link goes away before that point, the supplier's > > PM-runtime usage counter will remain nonzero. > > > > To prevent that from happening, first rework pm_runtime_get_suppliers() > > and pm_runtime_put_suppliers() to use the rpm_active refounts of device > > links and make the latter only drop rpm_active and the supplier's > > PM-runtime usage counter for each link by one, unless rpm_active is > > one already for it. Next, modify device_link_add() to bump up the > > new link's rpm_active refcount and the suppliers PM-runtime usage > > counter by two, to prevent pm_runtime_put_suppliers(), if it is > > called subsequently, from suspending the supplier prematurely (in > > case its PM-runtime usage counter goes down to 0 in there). > > > > Due to the way rpm_put_suppliers() works, this change does not > > affect runtime suspend of the consumer ends of new device links (or, > > generally, device links for which DL_FLAG_PM_RUNTIME has just been > > set). > > > > Fixes: e2f3cd831a28 ("driver core: Fix handling of runtime PM flags in device_link_add()") > > Reported-by: Ulf Hansson <ulf.hansson@linaro.org> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > I have tested a several various common probe sequences (including > error paths) by using my RPM test driver, no issues found. Of course > it also fixes the problem that occurred while deleting the device link > during ->probe(). Thanks a lot! > > Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org> > Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Thank you!
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