maria-developers team mailing list archive

[Oleksandr Byelkin <sanja@xxxxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxxx-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


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