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This bug is created as a clone of upstream ticket:
https://fedorahosted.org/389/ticket/47404
This causes errors like this in the errors log:
ldbm_back_add: modify_switch_entries failed
and
ldbm_back_modify: modify_switch_entries failed
The problem is that the struct _modify_context->old_entry can be removed from the cache between the call to ldbm_txn_ruv_modify_context() and the call to modify_switch_entries(), by a BETXN PRE Op plugin. Consider the following:
{{{
outer add:
ldbm_txn_ruv_modify_context:
mc->old_e = cached RUV ID = N DN = A
mc->new_e = not cached
betxnpreop - inner mod
ldbm_txn_ruv_modify_context:
mc->old_e = cached RUV ID = N DN = A # points to same cache entry as above old_e
mc->new_e = not cached
... do op - call modify_update_all()
... success ...
modify_switch_entries - cache_replace old_e, new_e
delete RUV ID from ID hash
delete RUV DN from DN hash
add new_e to RUV ID hash
add new_e to RUV DN hash
mark old_e as DELETED
new_e refcnt == 1 # NOTE: should this be new_e refcnt = old_e refcnt instead?
cache_return new_e - entrycache_return
new_e->refcnt-- # now 0
if (not DELETED)
add new_e to lru list
if (CACHE_FULL) # TRUE - cache is full
entrycache_flush - iterate through lru list
entrycache_remove_int new_e
remove RUV ID from ID hash
remove RUV DN from DN hash
mark new_e as DELETED
# NOTE: at this point, there is no RUV ID or DN in cache!
backentry_free(new_e)
outer
modify_switch_entries - cache_replace old_e, new_e
remove_hash RUV ID - FAIL
remove_hash RUV DN - FAIL
return 1 - FAIL
}}}
This most commonly happens with DNA as DNA is the only BETXN PREOP (in 1.2.11) that modifies the database.
After the call to the BETXN PREOP, we need to make sure mc->old_entry still points to something - not sure how best to do that.