rsync 2.6.3 hang (was rsync 2.6.2 crash)

jim jim at
Tue Oct 5 20:59:22 GMT 2004

Thanks for the additional info.

I actually have tried the --no-blocking-io option, but the sync still hung.

Since no one on Unix-like platforms are reporting an issue, do you think it may be 
something in the Cygwin compatibility layer?

Interestingly (to me anyway,) is that I have encountered the problem with syncing 
across the network using ssh, and syncing locally, but not over the network 
rsync to rsync. Maybe it's just a matter of time....

   -------Original Message-------
   > From: Wayne Davison <wayned at>
   > Subject: Re: rsync 2.6.3 hang (was rsync 2.6.2 crash)
   > Sent: 05 Oct 2004 10:06:15
   >  On Tue, Oct 05, 2004 at 07:07:17AM -0700, jim wrote:
   >  > Can you explain to me the relationship between the parent rsync
   >  > process and it's children?
   >  Rsync has a separate process for each major function.
   >  The generator process (on the receiving side) has the job of figuring
   >  out which files are different and sending checksum data for all the
   >  files it wants to see updated.  It sends that data to the sender.
   >  The sender has the job of taking the checksum data and generating a
   >  stream of data that can be used to recreate the sender's file using the
   >  receiver's file as a source of data.  It talks to the receiver process
   >  (which is on the same system as the generator, and which actually
   >  spawned the generator when things were starting up).
   >  The receiver has the job of taking the update data from the sender and
   >  turning it into the final updated files.  The final bit of communication
   >  is that the receiver has a pipe between it and the generator that can be
   >  used to send the generator some messages that need to be forwarded to
   >  the sender (since it can't send things to the sender directly).
   >  All these channels are selected for reading and writing using the
   >  select() function.  Most of the processes are in a constant state of I/O
   >  blocking, which is just fine going from the generator to the sender to
   >  the receiver.  However, the channel from the receiver to the generator
   >  has to be kept unblocked by buffering any messages that appear so that
   >  rsync doesn't deadlock.  That should all be handled just fine unless
   >  there is a bug.
   >  In the trace output you sent, it looks like the sender is waiting to
   >  write to the socket, the receiver is waiting to read from the socket,
   >  and the generator is waiting simultaneously on reading the pipe and
   >  writing the socket, so I don't see anything wrong there.
   >  One thing you might try is specifying --no-blocking-io and see if that
   >  makes a difference in the hanging you're seeing.
   >  ..wayne..
   -------Original Message-------

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