This partially reverts commit 6479006e.

Remove the constant tpool::aio::N_PENDING, which has no
intrinsic meaning for the tpool.

tpool::aio::N_PENDING: Replaces OS_AIO_N_PENDING_IOS_PER_THREAD.
This limits two similar things: the number of outstanding requests
that a thread may io_submit(), and the number of completed requests
collected at a time by io_getevents().

In the asynchronous I/O interface, InnoDB is invoking io_getevents()
with a timeout value of half a second, and requesting exactly 1 event
at a time.

The reason to have such a short timeout is to facilitate shutdown.

We can do better: Use an infinite timeout, wait for a larger maximum
number of events. On shutdown, we will invoke io_destroy(), which
should lead to the io_getevents system call reporting EINVAL.

my_getevents(): Reimplement the libaio io_getevents() by only invoking
the system call. The library implementation would try to elide the
system call and return 0 immediately if aio_ring_is_empty() holds.
Here, we do want a blocking system call, not 100% CPU usage. Neither
do we want the aio_ring_is_empty() trigger SIGSEGV because it is
dereferencing some memory that was freed by io_destroy().

The greedy fetch_add(1) approach of read_trylock() may cause
starvation of a waiting write lock request. Let us use a
compare-and-swap for the read lock acquisition in order to
guarantee the progress of writers.

Since commit 30ea63b7
we actually depend on futex on Linux. Also, we depend on
std::atomic for even longer.

We always defined PFS_SKIP_BUFFER_MUTEX_RWLOCK, that is,
the latches of the buffer pool blocks were never instrumented
in PERFORMANCE_SCHEMA.

For some reason, the debug_latch (which enforce proper usage of
buffer-fixing in debug builds) was instrumented.

In commit bf3c862f we introduced
an assertion that may dereference a null pointer.

This regression was caught by running the following:
./mtr --parallel=auto --suite=innodb \
--mysqld=--loose-innodb-adaptive-hash-index

The adaptive hash index is disabled by default since
commit 88cdfc5c (MDEV-20487)
and hence the problem was not caught earlier.

The test seems to deterministically fail on RelWithDebInfo builds
due to a timeout in wait_condition.inc.

According to Matthias Leich (the original author of the test),
the failure rate would reduce if we disabled the purge of
transaction history by setting innodb_force_recovery=2.

For now, let us run this stress test on debug builds only.

fil_space_t::flush_low(): Define and declare without inline.

ut_is_2pow(): Remove UNIV_LIKELY. This is almost exclusively
used in debug assertions. UNIV_LIKELY is not compatible with
static_assert in some compilers.

pipeline in community BB

Fix for rebuild from source step

Disable MCS on i386|i686 platforms

This patch puts MCS debian packaging files and part of debian/control
into the engine directory

Centos/RHEL7 have the MAP_HUGE_SHIFT constant
defined in linux/mman.h which needed to get included.

When MDEV-19544 (commit 1a6f4704)
simplified the initialization of the local variable
set_also_gap_locks, an inadvertent change was included.
Essentially, all code branches that are executed when
set_also_gap_locks hold must also ensure that
trx->isolation_level > TRX_ISO_READ_COMMITTED holds.
This was being violated in a few code paths.

It turns out that there is an even simpler fix: Remove the test
of thd_is_select() completely. In that way, the first part of
UPDATE or DELETE should work exactly like SELECT...FOR UPDATE.

thd_is_select(): Remove.

Starting with commit 7cffb5f6 (MDEV-23399)
the function buf_flush_page() will first acquire block->lock and only
after that invoke set_io_fix(). Before that, it was possible to reach
a livelock between buf_page_create() and buf_flush_page().

buf_page_create(): Directly try acquiring the exclusive page latch
without checking whether the page is io-fixed or buffer-fixed.
(As a matter of fact, the have_x_latch() check is not strictly necessary,
because we still support recursive X-latches.)
In case of a latch conflict, wait while allowing buf_page_write_complete()
to acquire buf_pool.mutex and release the block->lock.

An attempt to wait for exclusive block->lock while holding buf_pool.mutex
would lead to a hang in the tests parts.part_supported_sql_func_innodb
and stress.ddl_innodb, due to a deadlock between buf_page_write_complete()
and buf_page_create().

Similarly, in case of an I/O fixed compressed-only
ROW_FORMAT=COMPRESSED page, we will sleep before retrying.

In both cases, we will sleep for 1ms or until a flush batch is completed.

The data member tv_usec of the struct timeval is declared as suseconds_t
on MacOS. Size of suseconds_t is 4 bytes. On the other hand, size of ulong
is 8 bytes on 64-bit MacOS, so attempt to assign a value of wider type
(usec) to a value (tv_usec) of narrower type leads to error.

MDEV-23610: Slave user can't run "SHOW SLAVE STATUS" anymore after upgrade to 10.5, mysql_upgrade should take of that

Post push fix. Update version to 10.5.8.

This allows MariaDB to compile on old (limits to >2.6.32)
linux kernel versions.

This warns that attempts to use large pages will rely on
implict kernel determination.

This reverts commit 6cf8f05f.

Original patch assumed that MAP_HUGETLB as consistent across
achitectures which isn't the case. Defining it unconditionally
broke large pages on every achitecutre where the value differed
from x86_64.

With the EOL for Centos/RHEL6 announced in 10.5.7, <3.8 linux
kernels are no longer supported.

Account for variety of mips, hppa, solaris and other messages.

Copied from rpl.rpl_drop_db test.

MDEV-23610: Slave user can't run "SHOW SLAVE STATUS" anymore after upgrade to 10.5, mysql_upgrade should take of that

Fixing a post push test issue.

MDEV-23610: Slave user can't run "SHOW SLAVE STATUS" anymore after upgrade to 10.5, mysql_upgrade should take of that

Add a new privilege "SLAVE MONITOR" which will grant user the permission
to execute "SHOW SLAVE STATUS" and "SHOW RELAYLOG EVENTS" commands.

SHOW SLAVE STATUS requires either SLAVE MONITOR/SUPER
SHOW RELAYLOG EVENTS requires SLAVE MONITOR privilege.

into the engine directory

remove version data from the test output