[Monotone-devel] cvssync freeze

[William Uther]

Hi all,

  Again, this is probably most relevant to Christof Petig... I've  
just committed a test to the n.v.m.cvssync.refactor branch that  
causes a freeze in mtn_cvs pull.  The test is skipped just before the  
line that freezes.

  I've traced the problem back to mtn_automate::get_sync_info().  I  
generate a revision in mtn that has cvs: attributes, as well as a  
cert with sync info.  The cert appears to only contain cvs revision  
info for some of the files.  This manifests itself in  
cvs_repository::update() during a pull because the 'last' variable,  
that should contain the last cvs revision we synced with, is empty.   
That then causes the "Inconsistency" on line 450 to show up.  That in  
turn fails an invariant which when thrown doesn't close all the  
various pipes correctly and leads to the freeze.

  So there are at least two problems here:

  i) Either mtn_automate::get_sync_info() should be falling back to  
file attributes when the cert doesn't contain the info it needs, or
     Whatever writes the sync info into the cert needs to add sync  
info for all files in the revision.  (I suspect the first option here  
is better - it is backwards compatible with people who have already  
hit this problem, and it is more space efficient.)

and,

  ii) Failing an invariant should cause a clean windup, not a freeze  
where the child and parent process are each waiting on the other.

  Which of the solutions to i) do you think is better?

Cheers,

Will           :-}