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Fix conversion of ctypes pointers passed to C extension #154

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Merged
Araneidae merged 3 commits into from
Mar 12, 2024
Merged

Fix conversion of ctypes pointers passed to C extension #154

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df92d94
Fix conversion of ctypes pointers passed to C extension
Araneidae Mar 12, 2024
57790d4
Wrap comment going over 80 column limit
Araneidae Mar 12, 2024
d55483d
Update change log
Araneidae Mar 12, 2024
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24 changes: 15 additions & 9 deletions softioc/extension.c
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Original file line number Diff line number Diff line change
Expand Up @@ -98,9 +98,12 @@ static PyObject *db_put_field(PyObject *self, PyObject *args)
{
const char *name;
short dbrType;
void *pbuffer;
PyObject *buffer_ptr;
long length;
if (!PyArg_ParseTuple(args, "shnl", &name, &dbrType, &pbuffer, &length))
if (!PyArg_ParseTuple(args, "shOl", &name, &dbrType, &buffer_ptr, &length))
return NULL;
void *pbuffer = PyLong_AsVoidPtr(buffer_ptr);
if (!pbuffer)
return NULL;

struct dbAddr dbAddr;
Expand All @@ -110,11 +113,11 @@ static PyObject *db_put_field(PyObject *self, PyObject *args)

long put_result;
/* There are two important locks to consider at this point: The Global
* Interpreter Lock (GIL) and the EPICS record lock. A deadlock is possible if
* this thread holds the GIL and wants the record lock (which happens inside
* dbPutField), and there exists another EPICS thread that has the record lock
* and wants to call Python (which requires the GIL).
* This can occur if this code is called as part of an asynchronous on_update
* Interpreter Lock (GIL) and the EPICS record lock. A deadlock is possible
* if this thread holds the GIL and wants the record lock (which happens
* inside dbPutField), and there exists another EPICS thread that has the
* record lock and wants to call Python (which requires the GIL). This can
* occur if this code is called as part of an asynchronous on_update
* callback.
* Therefore, we must ensure we relinquish the GIL while we perform this
* EPICS call, to avoid potential deadlocks.
Expand All @@ -133,9 +136,12 @@ static PyObject *db_get_field(PyObject *self, PyObject *args)
{
const char *name;
short dbrType;
void *pbuffer;
PyObject *buffer_ptr;
long length;
if (!PyArg_ParseTuple(args, "shnl", &name, &dbrType, &pbuffer, &length))
if (!PyArg_ParseTuple(args, "shOl", &name, &dbrType, &buffer_ptr, &length))
return NULL;
void *pbuffer = PyLong_AsVoidPtr(buffer_ptr);
if (!pbuffer)
return NULL;

struct dbAddr dbAddr;
Expand Down