[tor-bugs] #27331 [Core Tor/Tor]: Non-fatal assertion ent->cdm_diff_status != CDM_DIFF_PRESENT failed in cdm_diff_ht_check_and_note_pending at src/or/consdiffmgr.c:272

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#27331: Non-fatal assertion ent->cdm_diff_status != CDM_DIFF_PRESENT failed in
cdm_diff_ht_check_and_note_pending at src/or/consdiffmgr.c:272
--------------------------+------------------------------------
 Reporter:  a_p           |          Owner:  (none)
     Type:  defect        |         Status:  new
 Priority:  High          |      Milestone:  Tor: 0.3.5.x-final
Component:  Core Tor/Tor  |        Version:  Tor: 0.3.4.7-rc
 Severity:  Normal        |     Resolution:
 Keywords:  regression    |  Actual Points:
Parent ID:                |         Points:
 Reviewer:                |        Sponsor:
--------------------------+------------------------------------

Comment (by nickm):

 So, this means that in `consdiffmgr_rescan()`, we somehow added a value to
 `compute_diffs_from`, but later on we found a corresponding entry in
 cdm_diff_ht that indicated that we already had a value here.

 It might be the case that the old value had the same `target_sha3` (in
 which case we already did compute a value here!) or that the old value had
 a different `target_sha3` (in which case it should have been removed by
 `cdm_diff_ht_purge()`.

 Since we've only had one report here, this probably isn't super-frequent.
 Maybe we should log more about this case if it occurs, so we can see where
 the error is happening.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/27331#comment:6>
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