Re: unkillable process stuck in "nfsaio"

On Fri, Mar 17, 2006 at 01:26:13PM -0500, Rong-En Fan wrote:
> On 3/17/06, Kostik Belousov <kostikbel_at_gmail.com> wrote:
> > Just out of curiosity:
> >
> > could you, please, test this little patch:
> >
> > Index: sys/nfsclient/nfs_bio.c
> 
> I have been played around with intr/nointr with this patch + some in
> nfs_bio.c, nfs_vnops.c.
> Here are the results (note that, the revision # below means the
> changes made in that
> revision), tested on RELENG_6 as of yesterday, i386, SMP. kernel is built with
> INVARIANT on.
> 
> * nfs_vnops.c 1.262, nfs_bio.c 1.154
> 
> - intr
> 
> $ dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.410424 secs (11887474 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C^C^C^C^C^C^C^C^C^C7+0 records in
> 6+0 records out
> 6291456 bytes transferred in 291.017236 secs (21619 bytes/sec)
> (stuck in nfsaio)
> 
> - nointr
> 
> $ dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.264193 secs (12295128 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C12+0 records in
> 11+0 records out
> 11534336 bytes transferred in 0.990210 secs (11648373 bytes/sec)
> 
> * nfs_vnops.c 1.262
> 
> - intr
> 
> $dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.238704 secs (12369064 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C
> ^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^Ccc^C^C^C^C15+0 records in
> 14+0 records out
> 14680064 bytes transferred in 677.578696 secs (21665 bytes/sec)
> (stuck in nfsaio)
> 
> - nointr
> 
> $ dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.255155 secs (12321244 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C11+0 records in
> 10+0 records out
> 10485760 bytes transferred in 0.899381 secs (11658864 bytes/sec)
> 
> * nfs_vnops.c 1.262, nfs_bio.c (remove slpflag = 0)
> 
> - intr
> 
> $ dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.245185 secs (12350181 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C
> (top's state is changing between CPU0, CPU1, RUN, *Giant)
> (11 minutes passed, I reboot this box)
> 
> - nointr
> $ dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.454680 secs (11769375 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C17+0 records in
> 16+0 records out
> 16777216 bytes transferred in 1.458180 secs (11505587 bytes/sec)
> 
> * nfs_vnops.c 1.262, nfs_bio.c 1.154 (remove slpflags = 0)
> 
> - intr
> $ dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.386083 secs (11953445 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C^C
> (top's state is changing between CPU0, CPU1, RUN, *Giant)
> (44 minutes passwd, I rebooted)
> 
> - noitntr
> $ dd if=/dev/zero of=b bs=1m count=50
> 50+0 records in
> 50+0 records out
> 52428800 bytes transferred in 4.370959 secs (11994805 bytes/sec)
> $ dd if=/dev/zero of=b bs=1m count=50
> ^C25+0 records in
> 24+0 records out
> 25165824 bytes transferred in 2.122789 secs (11855076 bytes/sec)
> 
> Looks like that the changes to nfs_vnops.c last Nov by ps_at_, ^C can really stop
> the process, but it take too much time :(
> 
> Hope this helps,
> Rong-En Fan

Hmm, it seems there are another places to loop forever, e.g,
in nfs_bioread(), line 462 or 656. I think that exit on signal from
nfs_asyncio() shall cause exit from nfs_bioread too.

Sorry, I cannot make the patch now. Will look at this at the
next week, if nobody comes out with patch.