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Add INJECTION_POINT_CACHED() to run injection points directly from cache

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This new macro is able to perform a direct lookup from the local cache
of injection points (refreshed each time a point is loaded or run),
without touching the shared memory state of injection points at all.

This works in combination with INJECTION_POINT_LOAD(), and it is better
than INJECTION_POINT() in a critical section due to the fact that it
would avoid all memory allocations should a concurrent detach happen
since a LOAD(), as it retrieves a callback from the backend-private
memory.

The documentation is updated to describe in more details how to use this
new macro with a load.  Some tests are added to the module
injection_points based on a new SQL function that acts as a wrapper of
INJECTION_POINT_CACHED().

Based on a suggestion from Heikki Linnakangas.

Author: Heikki Linnakangas, Michael Paquier
Discussion: https://postgr.es/m/58d588d0-e63f-432f-9181-bed29313dece@iki.fi
This commit is contained in:
Michael Paquier
2024-07-18 09:50:41 +09:00
parent 6159331acf
commit a0a5869a85
7 changed files with 69 additions and 7 deletions
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14
src/test/modules/injection_points/injection_points.c
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@@ -333,6 +333,20 @@ injection_points_run(PG_FUNCTION_ARGS)
PG_RETURN_VOID();
}
/*
* SQL function for triggering an injection point from cache.
*/
PG_FUNCTION_INFO_V1(injection_points_cached);
Datum
injection_points_cached(PG_FUNCTION_ARGS)
{
char *name = text_to_cstring(PG_GETARG_TEXT_PP(0));
INJECTION_POINT_CACHED(name);
PG_RETURN_VOID();
}
/*
* SQL function for waking up an injection point waiting in injection_wait().
*/