uninterruptible sleep with rsync 2.5.4

[Laurent MONIN]

On Thu, Jun 13, 2002 at 12:27:40PM -0500, Dave Dykstra wrote:
> On Wed, Jun 12, 2002 at 05:41:41PM +0200, Laurent MONIN wrote:
> > Hi,
> > 
> > 	I've encountered a strange issue, difficult to reproduce for
> > now. I'm searching from where it comes.
> > 
> > Here are some facts:
> > - all programs are compiled from sources using gcc 2.95.3/glibc2.2.x
> >   and run on a i686 LFS linux system.
> 
> By LFS do you mean "Linux From Scratch"?
>
Yes. 
> > - rsync doesn't run above ssl.
> > - using rsync 2.5.4 as server to backup mailboxes on another computer.
> >   rsync daemon is launched from xinetd, rsync client from a cron job. 
> > - beside this rsync server, i've got a pop3 daemon that access these
> >   mailboxes.
> > - when mailbox is opened by pop3 and rsync daemons, both processes ends
> >   in uninterruptible sleep.
> > - When a new rsync client request arrives, another rsync daemon is
> >   launched and goes in uninterruptible sleep too -> reboot is required.
> > - mailbox is locked by pop3 using fcntl() and F_RDLCK mode.
> > - pop3 server writes modified mailbox to a temporary file then rename()
> >   it to mailbox name.
> > 
> > What's the behavior of rsync when a file is renamed while it reads it ?
> 
> It shouldn't notice, assuming you're on a local filesystem and not an
> NFS filesystem, because the system should keep the inode open until rsync
> closes it.
>
NFS isn't used here, so it shouldn't be a problem.
> > What's the behavior of rsync when a file is removed while it reads it ?
> 
> Same as the rename.
> 
Ack.
> > What's the behavior of rsync when a file is modified while it reads it ?
> 
> Depending on the modification, it will either not notice, generate an error,
> or copy inconsistent data.
> 
Ok.
> > I didn't try with latest rsync version yet and still have difficulties
> > to reproduce this issue but i would like to have your opinion about
> > that.

rsync doesn't use any lock system on files it reads, right ?

I tried to reproduce that issue using rsync-2.5.4/rsync-2.5.5 on another
system without success for now. I'm still searching in which precise
conditions this issue is created.

Do you know any case in which rsync may be caught on uninterruptible sleep ?

Thanks for your help.

-- 

Laurent MONIN
Systèmes & Réseaux
Metaconcept Sarl
http://www.metaconcept.com