From b8b6d0c2c63bcd9252ce20ef990da093dda8b8ce Mon Sep 17 00:00:00 2001
From: Guido van Rossum <guido@python.org>
Date: Sat, 28 Jun 2003 21:53:52 +0000
Subject: Add PyThreadState_SetAsyncExc(long, PyObject *).

A new API (only accessible from C) to interrupt a thread by sending it
an exception.  This is not always effective, but might help some people.
Requested by Just van Rossum and Alex Martelli.  It is intentional
that you have to write your own C extension to call it from Python.

Docs will have to wait.
---
 Python/pystate.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

(limited to 'Python/pystate.c')

diff --git a/Python/pystate.c b/Python/pystate.c
index b083f8cb94..e8cb547156 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -143,6 +143,8 @@ PyThreadState_New(PyInterpreterState *interp)
 		tstate->use_tracing = 0;
 		tstate->tick_counter = 0;
 		tstate->gilstate_counter = 0;
+		tstate->async_exc = NULL;
+		tstate->thread_id = PyThread_get_thread_ident();
 
 		tstate->dict = NULL;
 
@@ -179,6 +181,7 @@ PyThreadState_Clear(PyThreadState *tstate)
 	ZAP(tstate->frame);
 
 	ZAP(tstate->dict);
+	ZAP(tstate->async_exc);
 
 	ZAP(tstate->curexc_type);
 	ZAP(tstate->curexc_value);
@@ -296,6 +299,32 @@ PyThreadState_GetDict(void)
 }
 
 
+/* Asynchronously raise an exception in a thread.
+   Requested by Just van Rossum and Alex Martelli.
+   To prevent naive misuse, you must write your own exception
+   to call this.  Must be called with the GIL held.
+   Returns the number of tstates modified; if it returns a number
+   greater than one, you're in trouble, and you should call it again
+   with exc=NULL to revert the effect.  This raises no exceptions. */
+
+int
+PyThreadState_SetAsyncExc(long id, PyObject *exc) {
+	PyThreadState *tstate = PyThreadState_Get();
+	PyInterpreterState *interp = tstate->interp;
+	PyThreadState *p;
+	int count = 0;
+	for (p = interp->tstate_head; p != NULL; p = p->next) {
+		if (p->thread_id != id)
+			continue;
+		ZAP(p->async_exc);
+		Py_XINCREF(exc);
+		p->async_exc = exc;
+		count += 1;
+	}
+	return count;
+}
+
+
 /* Routines for advanced debuggers, requested by David Beazley.
    Don't use unless you know what you are doing! */
 
@@ -320,6 +349,7 @@ PyThreadState_Next(PyThreadState *tstate) {
 	return tstate->next;
 }
 
+
 /* Python "auto thread state" API. */
 #ifdef WITH_THREAD
 
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