Re: Plugins redux (was Re: [PATCHES] PL instrumentation

On Wed, 2006-08-09 at 12:44 -0400, Tom Lane wrote:
> A plugin such as a plpgsql debugger would do this in its _PG_init()
> function:
>
> static PLpgSQL_plugin my_plugin = { ... function addresses ... };
>
> PLpgSQL_plugin **var_ptr;
>
> var_ptr = (PLpgSQL_plugin **) find_rendezvous_variable("PLpgSQL_plugin");
> *var_ptr = &my_plugin;
>
> and this in its _PG_fini() function:
>
> PLpgSQL_plugin **var_ptr;
>
> var_ptr = (PLpgSQL_plugin **) find_rendezvous_variable("PLpgSQL_plugin");
> *var_ptr = NULL;
>
> Meanwhile, plpgsql itself would do this in its _PG_init() function:
>
> static PLpgSQL_plugin **plugin_ptr = NULL;
>
> plugin_ptr = (PLpgSQL_plugin **) find_rendezvous_variable("PLpgSQL_plugin");
>
> and in the places where it wants to pass control to the plugin, it'd do
>
> if (*plugin_ptr)
> ((*plugin_ptr)->function_field) (... args ...);
>

I know this is a trivial question, but is there some kind of lock that
would prevent the PG_fini for the plpgsql debugger from executing after
"if(*plugin_ptr)" and before "((*plugin_ptr)->function_field)(...)"?

Regards,
Jeff Davis