Hi, Sergey! 08.02.2014 18:50, Sergey Vojtovich пишет:
Hi Sanja,
JFYI: while reporting this bug I came up with two questions that I couldn't answer quickly. Probably they make sense, if not just ignore them:
1. This code was introduced with https://bugs.launchpad.net/maria/+bug/782223, revision: wlad@montyprogram.com-20110514163720-rmico2qegtptjguk <quot> The callstack leading of "free" containing critical section is: mysqld!free my_no_flags_free Query_cache::free_cache Query_cache::resize fix_query_cache_size set_var::update sql_set_variables mysql_execute_command mysql_parse <quot>
It means that this code was supposed to be executed exactly by Query_cache::resize(), where you disable it.
Question: if this code is not supposed to be executed by ::resize(), is it needed at all?
It makes some other things so probably it is needed (and as can see stack it was more about whole cache, but of course I can't revise head of Wlad :)
2. In Query_cache::resize() I can see block-level locks are acquired with the following comment: <quot> Wait for all readers and writers to exit. When the list of all queries is iterated over with a block level lock, we are done. </quot>
Isn't it needed in ::free_cache() also?
Free cache used in 1) init (it definitely do not need) 2) unlock with check that there is no requests (when switching cache off) 3) destruction here (as I think) all clients should be disconnected already because of server shutdown. 4) resize (but here you see that it was locked and unlocked [skip]