Bug #50912 Assertion `ticket->m_type >= mdl_request->type' failed on HANDLER + I_S

Description:
Using I_S tables after HANDLER causes the following assertion:

mysqld: mdl.cc:1286: bool MDL_context::try_acquire_lock(MDL_request*): Assertion `ticket->m_type >= mdl_request->type' failed.

#6  0x000000315a42bec9 in __assert_fail () from /lib64/libc.so.6
#7  0x00000000008464ff in MDL_context::try_acquire_lock (this=0x2d27ce8, mdl_request=0x2e21c68) at mdl.cc:1286
#8  0x00000000006944e4 in open_table_get_mdl_lock (thd=0x2d27c18, table_list=0x2e21938, mdl_request=0x2e21c68, ot_ctx=0x7f82ea03c160, flags=514)
    at sql_base.cc:2390
#9  0x00000000006995bb in open_table (thd=0x2d27c18, table_list=0x2e21938, mem_root=0x7f82ea03c120, ot_ctx=0x7f82ea03c160, flags=514) at sql_base.cc:2664
#10 0x000000000069a835 in open_and_process_table (thd=0x2d27c18, lex=0x2d294b0, tables=0x2e21938, counter=0x7f82ea03c2ac, flags=514,
    prelocking_strategy=0x7f82ea03c230, has_prelocking_list=false, ot_ctx=0x7f82ea03c160, new_frm_mem=0x7f82ea03c120) at sql_base.cc:4176
#11 0x000000000069af6d in open_tables (thd=0x2d27c18, start=0x7f82ea03c270, counter=0x7f82ea03c2ac, flags=514, prelocking_strategy=0x7f82ea03c230)
    at sql_base.cc:4497
#12 0x000000000054af08 in open_tables (thd=0x2d27c18, tables=0x7f82ea03c270, counter=0x7f82ea03c2ac, flags=514) at mysql_priv.h:1538
#13 0x000000000069b3c0 in open_normal_and_derived_tables (thd=0x2d27c18, tables=0x2e21938, flags=514) at sql_base.cc:5150
#14 0x00000000007c5a8f in get_all_tables (thd=0x2d27c18, tables=0x2d83a98, cond=0x0) at sql_show.cc:3471
#15 0x00000000007b241a in get_schema_tables_result (join=0x2d8f0d8, executed_place=PROCESSED_BY_JOIN_EXEC) at sql_show.cc:6316
#16 0x00000000006d6c18 in JOIN::exec (this=0x2d8f0d8) at sql_select.cc:1801
#17 0x00000000006d3833 in mysql_select (thd=0x2d27c18, rref_pointer_array=0x2d29d00, tables=0x2d83a98, wild_num=1, fields=@0x2d29c38, conds=0x0, og_num=0,
    order=0x0, group=0x0, having=0x0, proc_param=0x0, select_options=2684619264, result=0x2d85758, unit=0x2d29550, select_lex=0x2d29b30)
    at sql_select.cc:2473
#18 0x00000000006d8ceb in handle_select (thd=0x2d27c18, lex=0x2d294b0, result=0x2d85758, setup_tables_done_option=0) at sql_select.cc:272
#19 0x0000000000645d43 in execute_sqlcom_select (thd=0x2d27c18, all_tables=0x2d83a98) at sql_parse.cc:4571
#20 0x00000000006472a8 in mysql_execute_command (thd=0x2d27c18) at sql_parse.cc:2043
#21 0x000000000064ebc0 in mysql_parse (thd=0x2d27c18, inBuf=0x2d83888 "SELECT * FROM information_schema . tables", length=41, found_semicolon=0x7f82ea03ef10)
    at sql_parse.cc:5584
#22 0x000000000064f7d9 in dispatch_command (command=COM_QUERY, thd=0x2d27c18, packet=0x2d7b7f9 "SELECT * FROM information_schema . tables ",
    packet_length=42) at sql_parse.cc:1008
#23 0x0000000000650c3c in do_command (thd=0x2d27c18) at sql_parse.cc:694
#24 0x000000000063f354 in handle_one_connection (arg=0x2d27c18) at sql_connect.cc:1163
#25 0x000000315b0073da in start_thread () from /lib64/libpthread.so.0
#26 0x000000315a4e627d in clone () from /lib64/libc.so.6

How to repeat:
CREATE TABLE IF NOT EXISTS t1 (f1 integer);
HANDLER t1  OPEN AS A;
SELECT * FROM information_schema . tables ;

HANDLER OPEN acquires a metadata lock of type MDL_SHARED.
The I_S query requests a MDL_SHARED_HIGH_PRIO lock.
The existing MDL_SHARED ticket is found in find_ticket() since
it satisfies ticket->has_stronger_or_equal_type(mdl_request->type).

However since MDL_SHARED_HIGH_PRIO < MDL_SHARED, this assert is
triggered right after. A similar assert would have been triggered
in clone_ticket() right afterwards.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/99478

3077 Jon Olav Hauglid	2010-02-05
      Bug #50912 Assertion `ticket->m_type >= mdl_request->type'
                 failed on HANDLER + I_S
      
      This assert was triggered when an I_S query tried to lock a table
      already locked by a HANDLER statement in the same connection. 
      
      First the HANDLER took a MDL_SHARED lock. Afterwards, the I_S query
      requested a MDL_SHARED_HIGH_PRIO lock. The existing MDL_SHARED ticket
      is found in find_ticket() since it satisfies 
      ticket->has_stronger_or_equal_type(mdl_request->type) as MDL_SHARED
      and MDL_SHARED_HIGH_PRIO have equal strengths, just different priority.
      
      However, two asserts later check lock type strengths using relational
      operators (>= and <=) rather than MDL_ticket::has_stronger_or_equal_type().
      These asserts are triggered since MDL_SHARED >= MDL_SHARED_HIGH_PRIORITY
      is false (mapped to 1 and 2 respectively).
      
      This patch updates the asserts to use MDL_ticket::has_stronger_or_equal_type()
      rather than relational operators to check lock type strength.
      
      Test case added to include/handler.inc.

Approved with minor comments sent by e-mail.

A patch for this bug has been committed. After review, it may
be pushed to the relevant source trees for release in the next
version. You can access the patch from:

  http://lists.mysql.com/commits/99538

3084 Jon Olav Hauglid	2010-02-06
      Bug #50912 Assertion `ticket->m_type >= mdl_request->type'
                 failed on HANDLER + I_S
      
      This assert was triggered when an I_S query tried to acquire a
      metadata lock on a table which was already locked by a HANDLER
      statement in the same connection.
      
      First the HANDLER took a MDL_SHARED lock. Afterwards, the I_S query
      requested a MDL_SHARED_HIGH_PRIO lock. The existing MDL_SHARED ticket
      is found in find_ticket() since it satisfies 
      ticket->has_stronger_or_equal_type(mdl_request->type) as MDL_SHARED
      and MDL_SHARED_HIGH_PRIO have equal strengths, just different priority.
      
      However, two asserts later check lock type strengths using relational
      operators (>= and <=) rather than MDL_ticket::has_stronger_or_equal_type().
      These asserts are triggered since MDL_SHARED >= MDL_SHARED_HIGH_PRIORITY
      is false (mapped to 1 and 2 respectively).
      
      This patch updates the asserts to use MDL_ticket::has_stronger_or_equal_type()
      rather than relational operators to check lock type strength.
      
      Test case added to include/handler.inc.

Pushed to mysql-next-4284.

Closing the bug as the patch adjusts two asserts that only exist in 
next-4284. Since this is an internal tree, no documentation changes
are necessary.

Pushed into 6.0.14-alpha (revid:alik@sun.com-20100216101445-2ofzkh48aq2e0e8o) (version source revid:kostja@sun.com-20100210211106-nq8ztcq2z9o4csit) (merge vers: 6.0.14-alpha) (pib:16)

Pushed into mysql-next-mr (revid:alik@sun.com-20100216101208-33qkfwdr0tep3pf2) (version source revid:kostja@sun.com-20100206103007-2te50xtpwd7o3spx) (pib:16)

Pushed into 5.5.3-m3 (revid:alik@sun.com-20100306103849-hha31z2enhh7jwt3) (version source revid:vvaintroub@mysql.com-20100216221947-luyhph0txl2c5tc8) (merge vers: 5.5.99-m3) (pib:16)

No changelog entry needed.