#At bzr+ssh://bk-internal.mysql.com/bzrroot/server/mysql-maria/ based on revid:sanja@stripped
2709 Guilhem Bichot 2008-11-27
Fix for BUG#40661 "Maria: crash in embedded server (when detecting deadlock?)"
bug is actually a weirdness in test system, so moving test portion into maria_notembedded.test
modified:
mysql-test/suite/maria/r/maria.result
mysql-test/suite/maria/r/maria_notembedded.result
mysql-test/suite/maria/t/maria.test
mysql-test/suite/maria/t/maria_notembedded.test
per-file messages:
mysql-test/suite/maria/r/maria.result
result update
mysql-test/suite/maria/r/maria_notembedded.result
result update
mysql-test/suite/maria/t/maria.test
Removing test portion into maria_notembedded.test. Explanation below.
Running maria.test with --mem --embedded --valgrind I got:
==378== Invalid read of size 4
==378== at 0x857C755: _lf_pinbox_real_free (lf_alloc-pin.c:342)
==378== by 0x857C640: _lf_pinbox_free (lf_alloc-pin.c:267)
==378== by 0x857D50C: ldelete (lf_hash.c:226)
==378== by 0x857DBC1: lf_hash_delete (lf_hash.c:429)
==378== by 0x8243D82: unlock_lock_and_free_resource
(waiting_threads.c:676)
==378== by 0x8244A79: wt_thd_release (waiting_threads.c:948)
==378== by 0x83F301D: wt_thd_release_self (trnman.c:98)
==378== by 0x83F3D49: trnman_end_trn (trnman.c:431)
==378== by 0x837C437: ma_commit (ma_commit.c:60)
==378== by 0x835F082: ha_maria::external_lock(THD*, int)
(ha_maria.cc:2387)
==378== by 0x84D1011: handler::ha_external_lock(THD*, int)
(handler.cc:4433)
==378== by 0x856DA92: unlock_external(THD*, st_table**, unsigned)
(lock.cc:786)
==378== by 0x856DD6F: mysql_unlock_tables(THD*, st_mysql_lock*)
(lock.cc:389)
==378== by 0x8274A57: close_thread_tables(THD*) (sql_base.cc:1307)
==378== by 0x82ABEC3: unlock_locked_tables(THD*) (sql_parse.cc:99)
==378== by 0x82B0BB3: mysql_execute_command(THD*)
(sql_parse.cc:3372)
==378== Address 0x5894a0c is 164 bytes inside a block of size 184
free'd
==378== at 0x40233FC: free (vg_replace_malloc.c:323)
==378== by 0x823CF92: my_thread_end (my_thr_init.c:348)
==378== by 0x8200FEE: mysql_thread_end (libmysql.c:250)
==378== by 0x81A9487: send_one_query (mysqltest.c:535)
==378== by 0x4050111: start_thread (in /lib/libpthread-2.5.so)
==378== by 0x41A52ED: clone (in /lib/libc-2.5.so)
(among other errors). The line where the invalid read happens is:
if (available_stack_size(&pinbox, *pins->stack_ends_here) >
alloca_size)
and stack_ends_here was previously set here:
el->stack_ends_here= & my_thread_var->stack_ends_here;
The mysqltest "send" command, in embedded mode, is implemented this way
(mysqltest.c:do_send_query()): a *new OS thread* is created in
mysqltest, and does this:
mysql_thread_init();
VOID(mysql_send_query(&cn->mysql, cn->cur_query,
cn->cur_query_len));
mysql_thread_end();
So, con_d "send insert t1 values (2)" creates a new OS thread, which
gets a thread-specific data (mysql_thread_init()), then sends the
query; in particular, this sets el->stack_ends_here to a pointer inside
the thread-specific data (see my_thread_var above), that is, thd->pins
depends on the thread-specific data.
This sent "insert" blocks as expected, thread-specific data is free()d
(my_thread_end() above), OS thread terminates.
Then "default" connection runs "insert t1 values (3)"
which blocks on the 3 already inserted by the con_d.
This blocking (see waiting_threads.c) creates a WT_RESOURCE, which has,
as owner, con_d's WT_THD.
When con_d calls "unlock tables" (see stack trace), it wants to release
this resource, which involves con_d's thd->pins, so it ends up reading
stack_ends_here which points inside the freed thread-specific data =>
Valgrind error, crashes...
So this is an effect of having one single connection (con_d) for which
two queries:
send insert t1 values (2)
unlock tables
are done by different OS threads. That is indeed weird design of
mysqltest, and it breaks on the dependency of lf_alloc-pin.c on
thread-specific data. It is maybe already explained in those comments
in lf_alloc-pin.c:
" It is assumed that pins belong to a THD and are not transferable
between THD's (LF_PINS::stack_ends_here being a primary reason
for this limitation)."
" It is assumed that pins belong to a thread and are not
transferable
between threads."
In correct usage of libmysqld (no two queries sent for one connection
by two threads), this problem would not happen, so I call it a
deficiency of the test system.
mysql-test/suite/maria/t/maria_notembedded.test
moving test portion into maria_notembedded.test
=== modified file 'mysql-test/suite/maria/r/maria.result'
--- a/mysql-test/suite/maria/r/maria.result 2008-10-15 12:44:31 +0000
+++ b/mysql-test/suite/maria/r/maria.result 2008-11-27 15:13:02 +0000
@@ -2203,19 +2203,6 @@ check table t2 extended;
Table Op Msg_type Msg_text
test.t2 check status OK
drop table t2;
-create table t1 (a int unique) transactional=1;
-insert t1 values (1);
-lock table t1 write concurrent;
-insert t1 values (2);
-lock table t1 write concurrent;
-insert t1 values (3);
-insert t1 values (2);
-insert t1 values (3);
-ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
-unlock tables;
-ERROR 23000: Duplicate entry '2' for key 'a'
-unlock tables;
-drop table t1;
CREATE TABLE t1 (
col0 float DEFAULT NULL,
col1 date DEFAULT NULL,
=== modified file 'mysql-test/suite/maria/r/maria_notembedded.result'
--- a/mysql-test/suite/maria/r/maria_notembedded.result 2008-10-11 08:27:03 +0000
+++ b/mysql-test/suite/maria/r/maria_notembedded.result 2008-11-27 15:13:02 +0000
@@ -23,3 +23,16 @@ select count(*) from t1;
count(*)
1
drop table t1;
+create table t1 (a int unique) transactional=1;
+insert t1 values (1);
+lock table t1 write concurrent;
+insert t1 values (2);
+lock table t1 write concurrent;
+insert t1 values (3);
+insert t1 values (2);
+insert t1 values (3);
+ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
+unlock tables;
+ERROR 23000: Duplicate entry '2' for key 'a'
+unlock tables;
+drop table t1;
=== modified file 'mysql-test/suite/maria/t/maria.test'
--- a/mysql-test/suite/maria/t/maria.test 2008-10-15 12:44:31 +0000
+++ b/mysql-test/suite/maria/t/maria.test 2008-11-27 15:13:02 +0000
@@ -1469,31 +1469,6 @@ insert into t2 values (repeat('x',28)),
check table t2 extended;
drop table t2;
-#
-# an example of a deadlock
-#
-create table t1 (a int unique) transactional=1;
-insert t1 values (1);
-lock table t1 write concurrent;
-insert t1 values (2);
-connect(con_d,localhost,root,,);
-lock table t1 write concurrent;
-insert t1 values (3);
-send insert t1 values (2);
-connection default;
-let $wait_condition=select count(*) = 1 from information_schema.processlist where state="waiting for a resource";
---source include/wait_condition.inc
---error ER_LOCK_DEADLOCK
-insert t1 values (3);
-unlock tables;
-connection con_d;
---error ER_DUP_ENTRY
-reap;
-unlock tables;
-disconnect con_d;
-connection default;
-drop table t1;
-
CREATE TABLE t1 (
col0 float DEFAULT NULL,
col1 date DEFAULT NULL,
=== modified file 'mysql-test/suite/maria/t/maria_notembedded.test'
--- a/mysql-test/suite/maria/t/maria_notembedded.test 2008-10-11 08:27:03 +0000
+++ b/mysql-test/suite/maria/t/maria_notembedded.test 2008-11-27 15:13:02 +0000
@@ -26,6 +26,34 @@ select * from t1;
select count(*) from t1;
drop table t1;
+# This cannot be run in embedded server, see BUG#40661, because
+# mysqltest runs "send" commands in separate OS thread.
+#
+# an example of a deadlock
+#
+create table t1 (a int unique) transactional=1;
+insert t1 values (1);
+lock table t1 write concurrent;
+insert t1 values (2);
+connect(con_d,localhost,root,,);
+lock table t1 write concurrent;
+insert t1 values (3);
+send insert t1 values (2);
+connection default;
+let $wait_condition=select count(*) = 1 from information_schema.processlist where state="waiting for a resource";
+--source include/wait_condition.inc
+--error ER_LOCK_DEADLOCK
+insert t1 values (3);
+unlock tables;
+connection con_d;
+--error ER_DUP_ENTRY
+reap;
+unlock tables;
+disconnect con_d;
+connection default;
+drop table t1;
+
+
--disable_result_log
--disable_query_log
eval set session storage_engine=$default_engine;
| Thread |
|---|
| • bzr commit into MySQL/Maria:mysql-maria branch (guilhem:2709) Bug#40661 | Guilhem Bichot | 27 Nov |
