On Friday, 20 July 2007 23:33, Jeremy Maitin-Shepard wrote: > "Rafael J. Wysocki" <rjw@xxxxxxx> writes: > > [snip] > > >> Or add a small bit of infrastructure that errors writes at make_request > >> if you don't have a magic "i am a direct block device write from > >> userspace" flag on the bio. > >> > >> The hibernate may fail, but you don't corrupt the media. > >> > >> If you don't get the image out, resume back to the "this is resume" > >> instead of the power-down path. > > > Well, I don't think that is much prettier than the freezer ... > > It seems that a better solution to the "how do we write to a file on an > in-use partition" has been suggested, which also handles swap partitions > and swap files, and does not require mounting filesystems, so it seems > that the filesystem issue need not be considered. > > [snip] > > > No. I'm saying that when you go back from the image-saving kernel to the > > hibernated kernel, you need to make sure that no task will cause any > > filesystem's on-disk state to be actually updated. If you can't make such > > a guarantee, you just can't do that. > > > With the current state of the drivers, it's not doable without the > > freezer. > > It seems that it should be feasible to fix the drivers so that > > 1. they can be taken from normal state to quiesced state without > requiring the freezer; > > 2. they can be taken from normal state to low power state without > requiring the freezer; Yes, that's correct. > 3. they can be taken from quiesced state to low power state without > requiring the freezer. > > In the particular, it seems that it should be possible to do (3) without > needing to schedule tasks. For that, you'd have to forbid the drivers to call schedule() from the relevant callbacks, which means, eg. no timeouts in there. > It seems likely that (2) may in fact be almost exactly the same as, or > at least similar to, (1) followed by (3), at least for many drivers. > (1) is required by the kexec hibernate approach even ignoring suspend to > both or S4. (2) is required for suspend to ram without the freezer, > which seems to be desired anyway. Yes, (2) is needed anyway. Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
