On Thu, 8 May 2014, Rafael J. Wysocki wrote: > > Wait a minute. Following ->runtime_suspend(), you are going to call > > ->suspend() and then ->runtime_resume()? That doesn't seem like what > > you really want; a ->suspend() call should always have a matching > > ->resume(). > > Yes, it should, but I didn't see any other way to do that. > > > I guess you did it this way to allow for runtime-resumes and -suspends > > between ->prepare() and ->suspend(), but it still seems wrong. > > No. I did that to allow ->suspend() to check whether or not the device is > in the right state. ->prepare() could do that, arguably, but then there's > the case when ->runtime_suspend() may still be running in parallel with it. > And the device may be runtime-suspended immediately before its ->suspend() > in theory if its children do pm_runtime_put_sync(parent). > > Also, this is a bus type ->suspend(), so the *driver* ->suspend() > won't be called at this point in the ACPI PM domain case for example. > > > How about asking drivers to set leave_runtime_suspended in their > > ->runtime_suspend() callbacks, as well as during ->prepare()? Then > > intervening runtime resume/suspend cycles wouldn't matter and you > > wouldn't need to call ->suspend(); you could skip it along with the > > other PM callbacks. > > That wouldn't work, because they cannot know the target sleep state of the > system in advance. This only is known during the given suspend sequence. Argh! We're both being foolish. Runtime suspends can't occur between ->prepare() and ->suspend(), because device_prepare() does a pm_runtime_get_noresume. You might still have to worry about a runtime suspend concurrent with ->prepare(), though. An appropriate barrier could fix that. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
