BIND 10 #2459: call to getCachedZoneWriter must be protected by mutex

[BIND 10 Development]

#2459: call to getCachedZoneWriter must be protected by mutex
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                   Reporter:         |                 Owner:  jinmei
  jinmei                             |                Status:  reviewing
                       Type:         |             Milestone:
  defect                             |  Sprint-20121120
                   Priority:         |            Resolution:
  medium                             |             Sensitive:  0
                  Component:         |           Sub-Project:  DNS
  b10-auth                           |  Estimated Difficulty:  3
                   Keywords:         |           Total Hours:  0
            Defect Severity:  High   |
Feature Depending on Ticket:         |
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Comment (by jinmei):

 Thanks for the review.

 Replying to [comment:8 muks]:
 > The code change itself looks fine to me, and `make check` (with the
 updated lock counts) passes. Lettuce also passes (though I suppose these
 don't test the specific problem).

 Right.  I suspect (reliably) reproducing the problem itself in
 unit/system tests is almost impossible.

 > I see that `doLoadZone()` grabs a lock on this mutex before calling
 `getCachedZoneWriter()`. Where does the main thread lock this mutex?

 Via `DataSrcClientsMgrBase::Holder`.  And, in practice, the only place
 in the main thread that acquires the lock is
 `AuthSrvImpl::processNormalQuery`.

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Ticket URL: <http://bind10.isc.org/ticket/2459#comment:9>
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