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Fix memory leaks in PL/Python.

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Previously, plpython was in the habit of allocating a lot of stuff in
TopMemoryContext, and it was very slipshod about making sure that stuff
got cleaned up; in particular, use of TopMemoryContext as fn_mcxt for
function calls represents an unfixable leak, since we generally don't
know what the called function might have allocated in fn_mcxt.  This
results in session-lifespan leakage in certain usage scenarios, as for
example in a case reported by Ed Behn back in July.

To fix, get rid of all the retail allocations in TopMemoryContext.
All long-lived allocations are now made in sub-contexts that are
associated with specific objects (either pl/python procedures, or
Python-visible objects such as cursors and plans).  We can clean these
up when the associated object is deleted.

I went so far as to get rid of PLy_malloc completely.  There were a
couple of places where it could still have been used safely, but on
the whole it was just an invitation to bad coding.

Haribabu Kommi, based on a draft patch by Heikki Linnakangas;
some further work by me
This commit is contained in:
Tom Lane
2015-11-05 13:52:30 -05:00
parent 64b2e7ad91
commit 8c75ad436f
15 changed files with 222 additions and 224 deletions
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30
src/pl/plpython/plpy_cursorobject.c
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@@ -8,6 +8,7 @@
#include "access/xact.h"
#include "mb/pg_wchar.h"
#include "utils/memutils.h"
#include "plpython.h"
@@ -111,7 +112,12 @@ PLy_cursor_query(const char *query)
return NULL;
cursor->portalname = NULL;
cursor->closed = false;
PLy_typeinfo_init(&cursor->result);
cursor->mcxt = AllocSetContextCreate(TopMemoryContext,
"PL/Python cursor context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
PLy_typeinfo_init(&cursor->result, cursor->mcxt);
oldcontext = CurrentMemoryContext;
oldowner = CurrentResourceOwner;
@@ -139,7 +145,7 @@ PLy_cursor_query(const char *query)
elog(ERROR, "SPI_cursor_open() failed: %s",
SPI_result_code_string(SPI_result));
cursor->portalname = PLy_strdup(portal->name);
cursor->portalname = MemoryContextStrdup(cursor->mcxt, portal->name);
PLy_spi_subtransaction_commit(oldcontext, oldowner);
}
@@ -200,7 +206,12 @@ PLy_cursor_plan(PyObject *ob, PyObject *args)
return NULL;
cursor->portalname = NULL;
cursor->closed = false;
PLy_typeinfo_init(&cursor->result);
cursor->mcxt = AllocSetContextCreate(TopMemoryContext,
"PL/Python cursor context",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
PLy_typeinfo_init(&cursor->result, cursor->mcxt);
oldcontext = CurrentMemoryContext;
oldowner = CurrentResourceOwner;
@@ -261,7 +272,7 @@ PLy_cursor_plan(PyObject *ob, PyObject *args)
elog(ERROR, "SPI_cursor_open() failed: %s",
SPI_result_code_string(SPI_result));
cursor->portalname = PLy_strdup(portal->name);
cursor->portalname = MemoryContextStrdup(cursor->mcxt, portal->name);
PLy_spi_subtransaction_commit(oldcontext, oldowner);
}
@@ -315,12 +326,13 @@ PLy_cursor_dealloc(PyObject *arg)
if (PortalIsValid(portal))
SPI_cursor_close(portal);
cursor->closed = true;
}
if (cursor->mcxt)
{
MemoryContextDelete(cursor->mcxt);
cursor->mcxt = NULL;
}
PLy_free(cursor->portalname);
cursor->portalname = NULL;
PLy_typeinfo_dealloc(&cursor->result);
arg->ob_type->tp_free(arg);
}