On Wednesday 03 March 2010, Alan Stern wrote: > On Wed, 3 Mar 2010, Pavel Machek wrote: > > > Hi! > > > > > > > The reason for freezing those tasks is to avoid writebacks at random > > > > > times during a system sleep transition, when the underlying device may > > > > > already be suspended, right? > > > > > > > > It is also there to avoid inconsistency between in-filesystem data and > > > > snapshot in hibernation image. > > > > > > A good point, although in this case I think it won't matter. Writing > > > out a dirty page twice (once right after taking the snapshot and then > > > again after resuming from hibernation) will leave the disk in a correct > > > state. > > > > No, I don't think so. Have you considered all the various journalling > > systems? > > > > Definitely not in presence of I/O errors. Commit block can only be > > written after previous blocks are successfully writen to the journal. > > > > So lets see: > > > > <snapshot> > > > > Write previous block, write commit block, write more blocks > > > > <hibernation powerdown, restart> > > > > Error writing previous block (block now contains garbage), leading to > > kernel panic > > > > <restart> > > > > journalling assumptions broken: commit block is there, but previous > > blocks are not intact. Data loss. > > > > ...and that was the first I could think about. Lets not do > > this. Barriers were invented for a reason. > > Very well. Then we still need a solution to the original problem: > Devices sometimes need to be unregistered during resume, but > del_gendisk() blocks on the writeback thread, which is frozen until > after the resume finishes. How do you suggest this be fixed? I thought about thawing the writeback thread earlier in such cases. Would that makes sense / is it doable at all? Rafael _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
