Re: (ITS#9097) lmdb: premature free of env->me_txn0

[hyc@symas.com]

Christopher Zimmermann wrote:
> Hi again,
> 
> I did some further debugging and now I'm afraid I am indeed finishing a
> transaction twice. I do call txn_commit() and after that I call
> txn_abort(). But the MDB_MAP_FULL event happens during mdb_txn_commit():
> 
> (gdb) frame 0
> #0  mdb_page_alloc (mc=0x7f7ffffbd580, num=1, mp=0x7f7ffffbd228) at mdb.c:2286
> 2286				rc = MDB_MAP_FULL;
> (gdb) bt
> #0  mdb_page_alloc (mc=0x7f7ffffbd580, num=1, mp=0x7f7ffffbd228) at mdb.c:2286
> #1  0x00000fb6fb6aa239 in mdb_page_touch (mc=0x7f7ffffbd580) at mdb.c:2428
> #2  0x00000fb6fb6a9db3 in mdb_page_search (mc=0x7f7ffffbd580, key=0x0, flags=5) at mdb.c:5627
> #3  0x00000fb6fb69e585 in mdb_freelist_save (txn=0xfb6bfb3ae00) at mdb.c:3087
> #4  0x00000fb6fb69c2a4 in mdb_txn_commit (txn=0xfb6bfb3ae00) at mdb.c:3612
> 
> mdb_txn_commit() will return MDB_MAP_FULL.
> 
> It may be worth adding MDB_MAP_FULL and MDB_BAD_TXN to the possible
> error codes of mdb_txn_commit(), or in general provide some guidance on
> how to clean up a txn after some failure.

The doc for commit and abort is explicit. A txn must not be used again after calling commit or abort.
There is nothing to clean up, the txn is always gone when commit or abort returns.

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