On Tuesday 27 December 2005 23:36, Patrick Mochel wrote: > > On Tue, 27 Dec 2005, Dmitry Torokhov wrote: > > > On 12/27/05, Patrick Mochel <mochel@xxxxxxxxxxxxxxxxxx> wrote: > > > > Would it be possible to simply mark the device as 'removed' and ignore it > > > until we resumed, and then clean it up (hotplug events and everything)? > > > > > > > Unfortunately swsusp resumes devices in the middle of suspend process > > with everything frozen and drivers don't know if they may clean up or > > have to postpone doing so. To do it uniformly you'd need to introduce > > threads and offload cleanups. I doubt it is good idea to require each > > subsystem to define cleanup thread or [ab]used keventd? > > Blech, I forgot about the caveman-like way of making sure the swap device > is resumed. :) > > Nevertheless, it shouldn't matter, and you bring up a point that exists, > and is actually more prevalent - the case of trying to resume a device > that doesn't exist any more. > > Last week, I suggested that all devices that are thought to be present > should be resumed. Those that have gone away should be removed once the > system is resumed, then new devices should be discovered. In this, I am > implying that devices that are thought to be there, but really aren't > (have been removed, unplugged, or undocked) should be marked as such > (somehow) and taken care of later. > > When swsusp resumes every device before writing the image, it should > ignore devices that aren't present anymore. They can still exist in > software (in the various object hiearchies), but they should just be > skipped. Ditto for when we 'suspend' them again, and on the real resume. > > When the system is back up and userspace is started again, something > should walk the device tree and reap the devices that are no longer > present. The core could do this, so long as the flag was in struct device, > though I'm not sure that it would know about the hooks to trigger a > removal on the device's bus (or would it need to?). Then, we can free all > the memory, do all the unregistering, and generate all the hotplug events. > > Of course, at that point, we'll need to discover any new devices, which is > going to be bus-speciifc. But, with a few extra bits of infrastructure > (per-bus objects, and a ->scan() method in struct bus_type), this will > relatively simple.. > > Thoughts? > I suppose... New devices will indeed have to be bus-specific but reaping function I think can be same for everyone - just call device_unregister() for every device that is marked as 'dead'. Unregister usually ignores all errors anyway. -- Dmitry
