Description:
This is an offshoot of Bug#20358 which is a bundle of hangs for various reason. This bug
deals with ::open() bug. The symptoms would be following:
1) InnoDB hanging on adaptive hash index with non-zero (typically 1) reader count.
<snip>
--Thread 1151424864 has waited at btr0sea.c line 995 for 265.00 seconds the semaphore:
X-lock on RW-latch at 0x2aaaaf3970b8 created in file btr0sea.c line 139
a writer (thread id 1151424864) has reserved it in mode wait exclusive
number of readers 1, waiters flag 1
</snip>
2) Find the thread holding the hash index latch by searching for "holds adaptive hash
latch" in .err
<snip>
---TRANSACTION 0 11972017, ACTIVE 329 sec, process no 32401, OS thread id 1164941664,
thread declared inside InnoDB 500
mysql tables in use 6, locked 0
, holds adaptive hash latch
MySQL thread id 54162, query id 45172395 172.16.12.6 ofmg Copying to tmp table
SELECT federation.name, federation.abbreviation, federation.type,
federation.colour_1, federation.colour_2, federation.colour_3,
federation.date_created, federation.membership_fee, federation.number_of_teams_joining,
federation.number_of_teams_joined,
IF(current_federation_member.organizer=1,federation.description,''),
federation.media_money_negotiated, federation.reputation, federation.locked,
founder_user.id, founder_user.name, founder_team.name,
IF(current_federation_member.user_id IS NULL,0,current_federation_member.organizer),
IF(current_federation_member.user_id IS NUL
Trx read view will not see trx with id >= 0 11972018, sees < 0 11970906
</snip>
3)Note the OS thread id (1164941664) above and see if the same thread is waiting for
dictionary mutex.
<snip>
--Thread 1164941664 has waited at dict0dict.c line 781 for 334.00 seconds the semaphore:
Mutex at 0x2aaaaf4858b8 created file dict0dict.c line 709, lock var 1
waiters flag 1
</snip>
If the above is true then we have hit ::open() bug.
Though MySQL should look into the real cause of calling ::open() while holding hash index
latch, we can fix the hang by releasing the adaptive hash latch unconditionally in
::open()
How to repeat:
see above.
