Hey, On Thu, Dec 26, 2013 at 01:42:29PM -0500, Alan Stern wrote: > In the case of hibernation, it's not so simple. We do need to perform > I/O, in order to save the memory image. But we also need to avoid > unnecessary I/O, in order to keep the on-disk data consistent with the > data in the memory image. You probably can't accomplish this at the > device driver or subsystem level. That was what I assumed too but Rafael tells me it has nothing to do with hibernation. > > which bothers me about the freezer is that it's essentially a separate > > entry point for suspend/resume implementation, and not a particularly > > well designed one at that. Things which depend on freezer for PM ops > > would need completely separate paths for runtime PM. They probably > > need some deviations anyway but freezer would push it unnecessarily. > > Maybe it's the other way around: The separate paths are necessary, and > the freezer _simplifies_ the system sleep ops. Again, the point is it's too big a tool given the problem with history of abuse. It sure is "convenient" to have tools at that level for that particular user - not because the task at hand fits such solution but because a lot more is being paid elsewhere. It just is out of proportion and isn't a good design in larger sense. As for autopm vs. system pm, there sure are necessary differences between the two but they also can share a lot. At least, it looks that way from libata side. I really don't think having two separate paradigms in implementing PM is a good idea even if the two paths have to deviate in significant ways. > Taking khubd as an example, I have to agree that converting it to a > workqueue would be a big simplification overall. And yet there are > some things khubd does which are (as far as I know) rather difficult to > accomplish with workqueues. One example in drivers/usb/core/hub.c: > kick_khubd() calls usb_autopm_get_interface_no_resume() if and only if > it added the hub to the event list (and it does so before releasing the > list's lock). How can you do that with a workqueue? Do the same thing and just replace wake_up() with queue_work()? Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
