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MDEV-10777: Server crashed due to query_cache_info plugin

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Possible fix. Make the pluging more safe.
This commit is contained in:
Oleksandr Byelkin
2016-09-14 18:15:03 +02:00
parent 3f5aedccca
commit e226276950
3 changed files with 42 additions and 9 deletions
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37
plugin/qc_info/qc_info.cc
View File

@ -106,6 +106,9 @@ static ST_FIELD_INFO qc_info_fields[]=
{0, 0, MYSQL_TYPE_STRING, 0, 0, 0, 0}
};
static const char unknown[]= "#UNKNOWN#";
static int qc_info_fill_table(THD *thd, TABLE_LIST *tables,
COND *cond)
{
@ -146,7 +149,8 @@ static int qc_info_fill_table(THD *thd, TABLE_LIST *tables,
query_cache_block_raw = my_hash_element(queries, i);
query_cache_block = (Query_cache_block*)query_cache_block_raw;
if (query_cache_block->type != Query_cache_block::QUERY)
if (unlikely(!query_cache_block ||
query_cache_block->type != Query_cache_block::QUERY))
continue;
query_cache_query = query_cache_block->query();
@ -169,14 +173,33 @@ static int qc_info_fill_table(THD *thd, TABLE_LIST *tables,
table->field[COLUMN_GROUP_CONCAT_MAX_LENGTH]->store(flags.group_concat_max_len, 0);
cs_client= get_charset(flags.character_set_client_num, MYF(MY_WME));
table->field[COLUMN_CHARACTER_SET_CLIENT]->store(cs_client->csname, strlen(cs_client->csname), scs);
if (likely(cs_client))
table->field[COLUMN_CHARACTER_SET_CLIENT]->
store(cs_client->csname, strlen(cs_client->csname), scs);
else
table->field[COLUMN_CHARACTER_SET_CLIENT]->
store(STRING_WITH_LEN(unknown), scs);
cs_result= get_charset(flags.character_set_results_num, MYF(MY_WME));
table->field[COLUMN_CHARACTER_SET_RESULT]->store(cs_result->csname, strlen(cs_result->csname), scs);
if (likely(cs_result))
table->field[COLUMN_CHARACTER_SET_RESULT]->
store(cs_result->csname, strlen(cs_result->csname), scs);
else
table->field[COLUMN_CHARACTER_SET_RESULT]->
store(STRING_WITH_LEN(unknown), scs);
collation= get_charset(flags.collation_connection_num, MYF(MY_WME));
table->field[COLUMN_COLLATION]->store(collation->name, strlen(collation->name), scs);
if (likely(collation))
table->field[COLUMN_COLLATION]->
store(collation->name, strlen(collation->name), scs);
else
table->field[COLUMN_COLLATION]-> store(STRING_WITH_LEN(unknown), scs);
tz= flags.time_zone->get_name();
if (likely(tz))
table->field[COLUMN_TIMEZONE]->store(tz->ptr(), tz->length(), scs);
else
table->field[COLUMN_TIMEZONE]-> store(STRING_WITH_LEN(unknown), scs);
table->field[COLUMN_DEFAULT_WEEK_FORMAT]->store(flags.default_week_format, 0);
table->field[COLUMN_DIV_PRECISION_INCREMENT]->store(flags.div_precision_increment, 0);
@ -204,7 +227,8 @@ static int qc_info_fill_table(THD *thd, TABLE_LIST *tables,
/* If we have result blocks, process them */
first_result_block= query_cache_query->result();
if(first_result_block)
if(query_cache_query->is_results_ready() &&
first_result_block)
{
/* initialize so we can loop over the result blocks*/
result_block= first_result_block;
@ -231,7 +255,8 @@ static int qc_info_fill_table(THD *thd, TABLE_LIST *tables,
}
table->field[COLUMN_RESULT_BLOCKS_COUNT]->store(result_blocks_count, 0);
table->field[COLUMN_RESULT_BLOCKS_SIZE]->store(result_blocks_size, 0);
table->field[COLUMN_RESULT_BLOCKS_SIZE_USED]->store(result_blocks_size_used, 0);
table->field[COLUMN_RESULT_BLOCKS_SIZE_USED]->
store(result_blocks_size_used, 0);
if (schema_table_store_record(thd, table))
goto cleanup;

3
sql/sql_cache.cc
View File

@ -961,7 +961,7 @@ inline void Query_cache_query::unlock_reading()
void Query_cache_query::init_n_lock()
{
DBUG_ENTER("Query_cache_query::init_n_lock");
res=0; wri = 0; len = 0;
res=0; wri = 0; len = 0; ready= 0;
mysql_rwlock_init(key_rwlock_query_cache_query_lock, &lock);
lock_writing();
DBUG_PRINT("qcache", ("inited & locked query for block 0x%lx",
@ -1226,6 +1226,7 @@ void Query_cache::end_of_result(THD *thd)
query_cache.split_block(last_result_block,len);
header->found_rows(limit_found_rows);
header->set_results_ready(); // signal for plugin
header->result()->type= Query_cache_block::RESULT;
/* Drop the writer. */

9
sql/sql_cache.h
View File

@ -156,8 +156,9 @@ struct Query_cache_query
Query_cache_block *res;
Query_cache_tls *wri;
ulong len;
uint8 tbls_type;
unsigned int last_pkt_nr;
uint8 tbls_type;
uint8 ready;
Query_cache_query() {} /* Remove gcc warning */
inline void init_n_lock();
@ -177,6 +178,12 @@ struct Query_cache_query
{
return (((uchar*)this) + ALIGN_SIZE(sizeof(Query_cache_query)));
}
/**
following used to check if result ready in plugin without
locking rw_lock of the query.
*/
inline void set_results_ready() { ready= 1; }
inline bool is_results_ready() { return ready; }
void lock_writing();
void lock_reading();
bool try_lock_writing();