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LP bug#677407 / MySQL Bug#48883: Stale data from INNODB_LOCKS table.
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The innodb.innodb_information_schema test could fail sporadically due to
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the flawed logic in the INFORMATION_SCHEMA.INNODB_LOCKS caching
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The logic for how to check when to update the table cache for
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INNODB_LOCKS with real data was flawed. This could result in both not
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updating the cache often enough (when the table is queried repeatedly
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with less than 100 milliseconds in-between) resulting in stale data; as
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well as updating too often (when multiple queries against the table
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start at around the same time).
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Fixed by updating the "last updated" timestamp in the right place, when
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the cache is updated, not when it is read.
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I hereby grant Percona the following BSD license to this patch for
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inclusion in Percona Server:
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Copyright (c) 2010, Kristian Nielsen All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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* Neither the name of the author nor the names of its contributors
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may be used to endorse or promote products derived from this
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software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
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TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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--- a/storage/innodb_plugin/trx/trx0i_s.c
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+++ b/storage/innodb_plugin/trx/trx0i_s.c
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ullint last_read; /*!< last time the cache was read;
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measured in microseconds since
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- mutex_t last_read_mutex;/*!< mutex protecting the
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- last_read member - it is updated
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- inside a shared lock of the
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i_s_table_cache_t innodb_trx; /*!< innodb_trx table */
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i_s_table_cache_t innodb_locks; /*!< innodb_locks table */
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i_s_table_cache_t innodb_lock_waits;/*!< innodb_lock_waits table */
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@@ -1142,13 +1138,6 @@
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- /* Here we read cache->last_read without acquiring its mutex
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- because last_read is only updated when a shared rw lock on the
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- whole cache is being held (see trx_i_s_cache_end_read()) and
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- we are currently holding an exclusive rw lock on the cache.
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- So it is not possible for last_read to be updated while we are
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#ifdef UNIV_SYNC_DEBUG
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ut_a(rw_lock_own(&cache->rw_lock, RW_LOCK_EX));
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@@ -1246,6 +1235,12 @@
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/*===================================*/
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trx_i_s_cache_t* cache) /*!< in/out: cache */
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+#ifdef UNIV_SYNC_DEBUG
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+ ut_a(rw_lock_own(&cache->rw_lock, RW_LOCK_EX));
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if (!can_cache_be_updated(cache)) {
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@@ -1258,6 +1253,10 @@
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mutex_exit(&kernel_mutex);
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+ /* update cache last read time */
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+ now = ut_time_us(NULL);
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+ cache->last_read = now;
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@@ -1288,16 +1287,12 @@
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release trx_i_s_cache_t::rw_lock
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acquire trx_i_s_cache_t::rw_lock, S
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- acquire trx_i_s_cache_t::last_read_mutex
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- release trx_i_s_cache_t::last_read_mutex
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release trx_i_s_cache_t::rw_lock */
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rw_lock_create(&cache->rw_lock, SYNC_TRX_I_S_RWLOCK);
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cache->last_read = 0;
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- mutex_create(&cache->last_read_mutex, SYNC_TRX_I_S_LAST_READ);
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table_cache_init(&cache->innodb_trx, sizeof(i_s_trx_row_t));
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table_cache_init(&cache->innodb_locks, sizeof(i_s_locks_row_t));
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table_cache_init(&cache->innodb_lock_waits,
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@@ -1348,18 +1343,10 @@
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/*===================*/
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trx_i_s_cache_t* cache) /*!< in: cache */
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#ifdef UNIV_SYNC_DEBUG
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ut_a(rw_lock_own(&cache->rw_lock, RW_LOCK_SHARED));
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- /* update cache last read time */
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- now = ut_time_us(NULL);
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- mutex_enter(&cache->last_read_mutex);
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- cache->last_read = now;
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- mutex_exit(&cache->last_read_mutex);
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rw_lock_s_unlock(&cache->rw_lock);
added
removed
patches/bug677407.patch
