Hi Martin, On Fri, Apr 07, 2023 at 03:31:02PM +0200, Martin Kepplinger wrote: > Am Mittwoch, dem 05.04.2023 um 15:52 +0300 schrieb Sakari Ailus: > > Hi Martin, > > > > On Wed, Apr 05, 2023 at 11:29:03AM +0200, Martin Kepplinger wrote: > > > pm_runtime_get_if_in_use() does not only return nonzero values when > > > the device is in use, it can return a negative errno too. > > > > > > And especially during resuming from system suspend, when runtime pm > > > is not yet up again, this can very well happen. And in such a case > > > the subsequent pm_runtime_put() call would result in a refcount > > > underflow! > > > > I think this issue should have a more generic solution, it's very > > difficult > > to address this in drivers only with the current APIs. > > > > pm_runtime_get_if_in_use() will also return an error if runtime PM is > > disabled, so this patch will break the driver for that configuration. > > ok but the driver is currently broken for any *other* error returned by > pm_runtime_get_if_in_use() (than the runtime-PM disabled error). > > The execution-path during system-resume I'm interested in gets -EAGAIN > here. Would it be ok for you if I'd return early only for that one > error only here? I guess... but I think to address this in a way that's reasonable to drivers, we'll need improvements to runtime PM API. A largish number of drivers need changes and before doing that we should figure out exactly what should be done. I thought you could effectively trigger this issue by calling runtime PM resume/suspend functions before enabling runtime PM, but this seems to be a different case. -- Kind regards, Sakari Ailus
