On Aug 31 2022, Bernd Schubert <bernd.schubert@xxxxxxxxxxx> wrote: > On 8/30/22 08:31, Nikolaus Rath wrote: >> Hello, >> I am comparing the behavior of FUSE and NBD when attempting to hibernate >> the system. >> FUSE seems to be mostly compatible, I am able to suspend the system even >> when there is ongoing I/O on the fuse filesystem. >> > > .... > >> As far as I can tell, the problem is that while an NBD request is >> pending, the atsk that waits for the result (in this case *rsync*) is >> refusing to freeze. This happens even when setting a 5 minute timeout >> for freezing (which is more than enough time for the NBD request to >> complete), so I suspect that the NBD server task (in this case nbdkit) >> has already been frozen and is thus unable to make progress. >> However, I do not understand why the same is not happening for FUSE >> (with FUSE requests being stuck because the FUSE daemon is already >> frozen). Was I just very lucky in my tests? Or are tasks waiting for >> FUSE request in a different kind of state? Or is NBD a red-herring here, >> and the real trouble is with ZFS? >> It would be great if someone could shed some light on what's going on. > > I guess it is a generic issue also affecting fuse, see this patch > > https://lore.kernel.org/lkml/20220511013057.245827-1-dlunev@xxxxxxxxxxxx/ > > A bit down the thread you can find a reference to this ancient patch > > https://linux-kernel.vger.kernel.narkive.com/UeBWfN1V/patch-fuse-make-fuse-daemon-frozen-along-with-kernel-threads Interesting, thank you for the link! So it seems that I just got lucky with FUSE. Does anyone know in which order the kernel freezes processes by default? Could I perhaps work around the problem by calling the FUSE/NBD daemon something like "zzzzz_mydaemon"? Best, -Nikolaus -- GPG Fingerprint: ED31 791B 2C5C 1613 AF38 8B8A D113 FCAC 3C4E 599F »Time flies like an arrow, fruit flies like a Banana.«
