Bug #19403 Crash that happens during removing of database name from cache (#2)

Description:
Working on stress testing of 5.1 tree I found  case when mysql server crashes during removing of database name from cache. There was already registered very similar issue(BUG#12212) for mysql 5.0.

test-case:
-----------------------------------------------
drop table if exists tb2;

create table tb2(a1 int);
insert into tb2 values(1);

DROP DATABASE IF EXISTS test1;
CREATE DATABASE test1;

Backtrace:
------------------------------------------------
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 4508592 (LWP 26353)]
0x005da8c8 in strcmp () from /lib/tls/libc.so.6
(gdb) bt
#0  0x005da8c8 in strcmp () from /lib/tls/libc.so.6
#1  0x0822d6af in remove_db_from_cache (db=0x8eff098 "test1") at sql_base.cc:5866
#2  0x082c7396 in mysql_rm_db (thd=0xb720e8b8, db=0x8eff098 "test1", if_exists=true, silent=false)
    at sql_db.cc:788
#3  0x081fc2b7 in mysql_execute_command (thd=0xb720e8b8) at sql_parse.cc:3694
#4  0x08202399 in mysql_parse (thd=0xb720e8b8, inBuf=0x8eff038 "DROP DATABASE IF EXISTS test1", length=29)
    at sql_parse.cc:5894
#5  0x081f70d3 in dispatch_command (command=COM_QUERY, thd=0xb720e8b8,
    packet=0xb7211ef9 "DROP DATABASE IF EXISTS test1", packet_length=30) at sql_parse.cc:1741
#6  0x081f696f in do_command (thd=0xb720e8b8) at sql_parse.cc:1537
#7  0x081f5989 in handle_one_connection (arg=0xb720e8b8) at sql_parse.cc:1179
#8  0x006e0341 in start_thread () from /lib/tls/libpthread.so.0
#9  0x006396fe in clone () from /lib/tls/libc.so.6

How to repeat:
Run attached  test case

Test suite for reproducing of registerd issue

Attachment: bug19403.tar.gz (application/x-tgz, text), 354 bytes.

Below is instruction how to repeat reported issue.

To run attached test case you need:

1. Unpack attached archive in mysql-test directory 
tar xzfv suite-bug19403.tar.gz

2. Run following command:

./mysql-test-run --stress --stress-threads=10 --stress-test-count=1000 --stress-suite=bug19403 test19403

Please test in 4.1 and 5.0 before verifying.

I was able to repeat only on 5.1BK:

   
   Output of mysqltest:
   mysqltest: At line 8: query 'DROP DATABASE IF EXISTS test1' failed: 2013: Lost connection to MySQL server during query

------------------------------------------------------------------------------------

test_loop[0:1000 0:995]: TID 5 test: 'test19403'  Errors: No Errors. Test Passed OK

test_loop[0:1000 0:1000]: TID 1 test: 'test19403'  Errors: No Errors. Test Passed OK

test_loop[0:1000 0:998]: TID 6 test: 'test19403'  Errors: No Errors. Test Passed OK

test_loop[0:1000 0:999]: TID 10 test: 'test19403'  Errors: No Errors. Test Passed OK

test_loop[0:1000 0:996]: TID 8 test: 'test19403'  Errors: No Errors. Test Passed OK

EXIT
Ending Tests
Shutting-down MySQL daemon

Master shutdown finished
Slave shutdown finished
miguel@hegel:~/dbs/mysql-5.0/mysql-test> 
-----------------------------------------------------------------------------------------

miguel@hegel:~/dbs/mysql-4.1/mysql-test> ./mysql-test-run --stress --stress-threads=10 --stress-test-count=1000 --stress-suite=bug19403 test19403
Logging: ./mysql-test-run --stress --stress-threads=10 --stress-test-count=1000 --stress-suite=bug19403 test19403
Unrecognized option: --stress

Approved by email.

Pushed to 5.1.12

Noted in 5.1.12 changelog.

When DROP DATABASE was issued while concurrently issuing DROP TABLE
(or RENAME TABLE, CREATE TABLE LIKE or any other statement that
required a name lock) in another connection, the server crashed.