MDEV-30815 Printing a stack trace leaks file descriptors.
In situations where mariadbd emits a lot of stack traces it can
run out of file descriptors. Each time the pipe to the external
utility addr2line is opened, those file descriptor are never closed.
rec_init_offsets_comp_ordinary(), rec_init_offsets(),
rec_get_offsets_reverse(), rec_get_nth_field_offs_old():
Simplify some bitwise arithmetics to avoid conditional jumps,
and add branch prediction hints with the assumption that most
variable-length columns are short.
MDEV-30753 Possible corruption due to trx_purge_free_segment()
Starting with commit 0de3be8cfdfc26f5c236eaefe12d03c7b4af22c8 (MDEV-30671),
the field TRX_UNDO_NEEDS_PURGE lost its previous meaning.
The following scenario is possible:
(1) InnoDB is killed at a point of time corresponding to the durable
execution of some fseg_free_step_not_header() but not
trx_purge_remove_log_hdr().
(2) After restart, the affected pages are allocated for something else.
(3) Purge will attempt to access the newly reallocated pages when looking
for some old undo log records.
trx_purge_free_segment(): Invoke trx_purge_remove_log_hdr() as the first
thing, to be safe. If the server is killed, some pages will never be
freed. That is the lesser evil. Also, before each mtr.start(), invoke
log_free_check() to prevent ib_logfile0 overrun.
Added detection of memory overwrite with multi_malloc
This patch also fixes some bugs detected by valgrind after this
patch:
- Not enough copy_func elements was allocated by Create_tmp_table() which
causes an memory overwrite in Create_tmp_table::add_fields()
I added an ASSERT() to be able to detect this also without valgrind.
The bug was that TMP_TABLE_PARAM::copy_fields was not correctly set
when calling create_tmp_table().
- Aria::empty_bits is not allocated if there is no varchar/char/blob
fields in the table. Fixed code to take this into account.
This cannot cause any issues as this is just a memory access
into other Aria memory and the content of the memory would not be used.
- Aria::last_key_buff was not allocated big enough. This may have caused
issues with rtrees and ma_extra(HA_EXTRA_REMEMBER_POS) as they
would use the same memory area.
- Aria and MyISAM didn't take extended key parts into account, which
caused problems when copying rec_per_key from engine to sql level.
- Mark asan builds with 'asan' in version strihng to detect these in
not_valgrind_build.inc.
This is needed to not have main.sp-no-valgrind fail with asan.
MDEV-30671 InnoDB undo log truncation fails to wait for purge of history
It is not safe to invoke trx_purge_free_segment() or execute
innodb_undo_log_truncate=ON before all undo log records in
the rollback segment has been processed.
A prominent failure that would occur due to premature freeing of
undo log pages is that trx_undo_get_undo_rec() would crash when
trying to copy an undo log record to fetch the previous version
of a record.
If trx_undo_get_undo_rec() was not invoked in the unlucky time frame,
then the symptom would be that some committed transaction history is
never removed. This would be detected by CHECK TABLE...EXTENDED that
was impleented in commit ab0190101b0587e0e03b2d75a967050b9a85fd1b.
Such a garbage collection leak should be possible even when using
innodb_undo_log_truncate=OFF, just involving trx_purge_free_segment().
trx_rseg_t::needs_purge: Change the type from Boolean to a transaction
identifier, noting the most recent non-purged transaction, or 0 if
everything has been purged. On transaction start, we initialize this
to 1 more than the transaction start ID. On recovery, the field may be
adjusted to the transaction end ID (TRX_UNDO_TRX_NO) if it is larger.
The field TRX_UNDO_NEEDS_PURGE becomes write-only; only some debug
assertions that would validate the value. The field reflects the old
inaccurate Boolean field trx_rseg_t::needs_purge.
trx_undo_mem_create_at_db_start(), trx_undo_lists_init(),
trx_rseg_mem_restore(): Remove the parameter max_trx_id.
Instead, store the maximum in trx_rseg_t::needs_purge,
where trx_rseg_array_init() will find it.
trx_purge_free_segment(): Contiguously hold a lock on
trx_rseg_t to prevent any concurrent allocation of undo log.
trx_purge_truncate_rseg_history(): Only invoke trx_purge_free_segment()
if the rollback segment is empty and there are no pending transactions
associated with it.
trx_purge_truncate_history(): Only proceed with innodb_undo_log_truncate=ON
if trx_rseg_t::needs_purge indicates that all history has been purged.
