On Fri, 4 Jun 2010, Maxim Levitsky wrote: > On Thu, 2010-03-04 at 14:53 +0100, Pavel Machek wrote: > > Hi! > > > > > > 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? > > > > Avoid unregistering device during resume. Instead, return errors until > > resume is done and you can call del_gendisk? > > This won't help ether. The same driver needs to unregister perfectly > working device on suspend, because the user might replace the card > during suspend and fool the os. > There is a setting, CONFIG_MMC_UNSAFE_RESUME and I use it, but it isn't > default. People have generally agreed that the best answer is to have del_gendisk always thaw the writeback thread. > Anyway to revive that old thread, how about introducing new > del_gendisk_no_sync? > > A less safe version of del_gendisk, but which won't sync the filesystem. > Since driver knows that card is gone, there is no point of syncing it. > > (the sync is done by invalidate_partition, so some flag should be > propagated to it). That might work for mmc, but it wouldn't help other drivers subject to the same problem. Besides, it's subject to races. What if the card _isn't_ gone, but for some other reason the driver wants to unregister the device at a time when the writeback thread is frozen? Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
