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Bug#17083851 BACKPORT BUG#11765744 TO 5.1, 5.5 AND 5.6

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Description:
Original fix Bug#11765744 changed mutex to read write lock
to avoid multiple recursive lock acquire operation on 
LOCK_status mutex.  
On Windows, locking read-write lock recursively is not safe. 
Slim read-write locks, which MySQL uses if they are supported by
Windows version, do not support recursion according to their 
documentation. For our own implementation of read-write lock, 
which is used in cases when Windows version doesn't support SRW,
recursive locking of read-write lock can easily lead to deadlock
if there are concurrent lock requests.

Fix:  
This patch reverts the previous fix for bug#11765744 that used
read-write locks. Instead problem of recursive locking for
LOCK_status mutex is solved by tracking recursion level using 
counter in THD object and acquiring lock only once when we enter 
fill_status() function first time.
This commit is contained in:
prabakaran thirumalai
2013-07-30 09:44:11 +05:30
parent f7940e407a
commit d95e57a328
3 changed files with 20 additions and 2 deletions
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1
sql/sql_class.cc
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@@ -605,6 +605,7 @@ THD::THD()
Open_tables_state(refresh_version), rli_fake(NULL), rli_slave(NULL),
lock_id(&main_lock_id),
user_time(0), in_sub_stmt(0),
fill_status_recursion_level(0),
sql_log_bin_toplevel(false),
binlog_table_maps(0), binlog_flags(0UL),
table_map_for_update(0),