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| author | Marko Mäkelä <marko.makela@mariadb.com> | 2017-05-11 21:12:37 +0300 |
|---|---|---|
| committer | Marko Mäkelä <marko.makela@mariadb.com> | 2017-05-12 12:24:53 +0300 |
| commit | ff166093741df0bd91ba24e02714ef882073c51b (patch) | |
| tree | f06d20fa767a9f7ad36bb30ef93ac49f19b852a2 /storage/xtradb/buf/buf0lru.cc | |
| parent | 1c418df7228ff3eaa1f9a1d9d630cb46947da781 (diff) | |
| download | mariadb-git-ff166093741df0bd91ba24e02714ef882073c51b.tar.gz | |
MDEV-12674 Innodb_row_lock_current_waits has overflow
There is a race condition related to the variable
srv_stats.n_lock_wait_current_count, which is only
incremented and decremented by the function lock_wait_suspend_thread(),
The incrementing is protected by lock_sys->wait_mutex, but the
decrementing does not appear to be protected by anything.
This mismatch could allow the counter to be corrupted when a
transactional InnoDB table or record lock wait is terminating
roughly at the same time with the start of a wait on a
(possibly different) lock.
ib_counter_t: Remove some unused methods. Prevent instantiation for N=1.
Add an inc() method that takes a slot index as a parameter.
single_indexer_t: Remove.
simple_counter<typename Type, bool atomic=false>: A new counter wrapper.
Optionally use atomic memory operations for modifying the counter.
Aligned to the cache line size.
lsn_ctr_1_t, ulint_ctr_1_t, int64_ctr_1_t: Define as simple_counter<Type>.
These counters are either only incremented (and we do not care about
losing some increment operations), or the increment/decrement operations
are protected by some mutex.
srv_stats_t::os_log_pending_writes: Document that the number is protected
by log_sys->mutex.
srv_stats_t::n_lock_wait_current_count: Use simple_counter<ulint, true>,
that is, atomic inc() and dec() operations.
lock_wait_suspend_thread(): Release the mutexes before incrementing
the counters. Avoid acquiring the lock mutex if the lock wait has
already been resolved. Atomically increment and decrement
srv_stats.n_lock_wait_current_count.
row_insert_for_mysql(), row_update_for_mysql(),
row_update_cascade_for_mysql(): Use the inc() method with the trx->id
as the slot index. This is a non-functional change, just using
inc() instead of add(1).
buf_LRU_get_free_block(): Replace the method add(index, n) with inc().
There is no slot index in the simple_counter.
Diffstat (limited to 'storage/xtradb/buf/buf0lru.cc')
| -rw-r--r-- | storage/xtradb/buf/buf0lru.cc | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/storage/xtradb/buf/buf0lru.cc b/storage/xtradb/buf/buf0lru.cc index 1aa2e7a9eb7..d31773c96cc 100644 --- a/storage/xtradb/buf/buf0lru.cc +++ b/storage/xtradb/buf/buf0lru.cc @@ -1,6 +1,7 @@ /***************************************************************************** Copyright (c) 1995, 2016, Oracle and/or its affiliates. All Rights Reserved. +Copyright (c) 2017, MariaDB Corporation. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software @@ -1501,7 +1502,7 @@ loop: n_iterations++; - srv_stats.buf_pool_wait_free.add(n_iterations, 1); + srv_stats.buf_pool_wait_free.inc(); /* In case of backoff, do not ever attempt single page flushes and wait for the cleaner to free some pages instead. */ @@ -1595,7 +1596,7 @@ loop: ++flush_failures; } - srv_stats.buf_pool_wait_free.add(n_iterations, 1); + srv_stats.buf_pool_wait_free.inc(); n_iterations++; |