Fixes https://github.com/ledgerwatch/erigon/issues/3874.
This was a minor regression after the c4a5325aafd3f03ce7520731b9da7253d7d178f0
that affects only debug builgs (with enabled assertions) and only when the added
code catch a incoherency of unified page/buffer cache.
The error was that the array of pointers in the transaction zeroed by the
value of env->me_numdbs and before txn->mt_numdbs was set to env->me_numdbs.
Thus, a cursor pointer(s) in the starting transaction could uninitialized if
another thread opened a dbi-handle(s) between the two aforementioned events.
The stable release with the complete workaround for an incoherence flaw of Linux unified page/buffer cache.
Nonetheless the cause for this trouble may be an issue of Intel CPU cache/MESI.
See [issue#269](https://github.com/erthink/libmdbx/issues/269) for more information.
Acknowledgements:
-----------------
- [David Bouyssié](https://github.com/david-bouyssie) for [Scala bindings](https://github.com/david-bouyssie/mdbx4s).
- [Michelangelo Riccobene](https://github.com/mriccobene) for reporting and testing.
Fixes:
------
- [Added complete workaround](https://github.com/erthink/libmdbx/issues/269) for an incoherence flaw of Linux unified page/buffer cache.
- [Fixed](https://github.com/erthink/libmdbx/issues/272) cursor reusing for read-only transactions.
- Fixed copy&paste typo inside `mdbx::cursor::find_multivalue()`.
Minors:
-------
- Minor refine C++ API for convenience.
- Minor internals refines.
- Added `lib-static` and `lib-shared` targets for make.
- Added minor workaround for AppleClang 13.3 bug.
- Clarified error messages of a signature/version mismatch.
Signed-off-by: Леонид Юрьев (Leonid Yuriev) <leo@yuriev.ru>
Briefly, this commit fixes a missed flaw:
- Cursor tracking is required to replacing shaded pages and adjusting the positions in writing transactions;
- Thus, historically, an internal linked list was maintained for a read-write transactions, but not for a read-only.
For this reason, the API for using cursors should be different for writing and reading transactions;
- However, the libmdbx's API has been significantly improved, including the ability to reuse cursors and a uniform cursors behavior for any kind of transactions.
My mistake is that due to working with MithrilDB, I forgot to make a same changes to libmdbx.
Fixes https://github.com/erthink/libmdbx/issues/272.
The stable release with the hotfix/workaround for a flaw of Linux 4.19 (at least) unified page/buffer cache.
See [issue#269](https://github.com/erthink/libmdbx/issues/269) for more information.
Acknowledgements:
-----------------
- [Simon Leier](https://github.com/leisim) for reporting and testing.
- [Kai Wetlesen](https://github.com/kaiwetlesen) for [RPMs](http://copr.fedorainfracloud.org/coprs/kwetlesen/libmdbx/).
- [Tullio Canepa](https://github.com/canepat) for reporting C++ API issue and contributing.
Fixes:
------
- [Added workaround](https://github.com/erthink/libmdbx/issues/269) for a flaw of Linux 4.19 (at least) unified page/buffer cache.
- [Fixed/Reworked](https://github.com/erthink/libmdbx/pull/270) move-assignment operators for "managed" classes of C++ API.
- Fixed potential `SIGSEGV` while open DB with overrided non-default page size.
- [Made](https://github.com/erthink/libmdbx/issues/267) `mdbx_env_open()` idempotence in failure cases.
- Refined/Fixed pages reservation inside `mdbx_update_gc()` to avoid non-reclamation in a rare cases.
- Fixed typo in a retained space calculation for the hsr-callback.
Minors:
-------
- Reworked functions for meta-pages, split-off non-volatile.
- Disentangled C11-atomic fences/barriers and pure-functions (with `__attribute__((__pure__))`) to avoid compiler misoptimization.
- Fixed hypotetic unaligned access to 64-bit dwords on ARM with `__ARM_FEATURE_UNALIGNED` defined.
- Reasonable paranoia that makes clarity for code readers.
- Minor fixes Doxygen references, comments, descriptions, etc.
Signed-off-by: Леонид Юрьев (Leonid Yuriev) <leo@yuriev.ru>
