python plugin: Fixing possible problems with the GIL.

If AfterFork is called after threads have been initialized.
Also handle SIGTERM while reading from an interactive session slightly more gracefully.

diff --git a/src/python.c b/src/python.c
index 1a7359cd526a5d9a5e7e725dc77671d88cf6d29d..27a1b25c4e1ecd14890cf6f81d8de7069ed26b81 100644 (file)
--- a/src/python.c
+++ b/src/python.c
@@ -925,7 +925,17 @@ static PyMethodDef cpy_methods[] = {
 static int cpy_shutdown(void) {
        PyObject *ret;
 
-       PyEval_RestoreThread(state);
+       if (!state) {
+               printf("================================================================\n");
+               printf("collectd shutdown while running an interactive session. This will\n");
+               printf("probably leave your terminal in a mess.\n");
+               printf("Run the command \"reset\" to get it back into a usable state.\n");
+               printf("You can press Ctrl+D in the interactive session to\n");
+               printf("close collectd and avoid this problem in the future.\n");
+               printf("================================================================\n");
+       }
+
+       CPY_LOCK_THREADS
 
        for (cpy_callback_t *c = cpy_shutdown_callbacks; c; c = c->next) {
                ret = PyObject_CallFunctionObjArgs(c->callback, c->data, (void *) 0); /* New reference. */
@@ -936,18 +946,23 @@ static int cpy_shutdown(void) {
        }
        PyErr_Print();
 
+       Py_BEGIN_ALLOW_THREADS
        cpy_unregister_list(&cpy_config_callbacks);
        cpy_unregister_list(&cpy_init_callbacks);
        cpy_unregister_list(&cpy_shutdown_callbacks);
        cpy_shutdown_triggered = 1;
+       Py_END_ALLOW_THREADS
 
-       if (!cpy_num_callbacks)
+       if (!cpy_num_callbacks) {
                Py_Finalize();
+               return 0;
+       }
 
+       CPY_RELEASE_THREADS
        return 0;
 }
 
-static void *cpy_interactive(void *data) {
+static void *cpy_interactive(void *pipefd) {
        PyOS_sighandler_t cur_sig;
 
        /* Signal handler in a plugin? Bad stuff, but the best way to
@@ -972,18 +987,18 @@ static void *cpy_interactive(void *data) {
         * This will make sure that SIGINT won't kill collectd but
         * still interrupt syscalls like sleep and pause. */
 
-       PyEval_AcquireThread(state);
        if (PyImport_ImportModule("readline") == NULL) {
                /* This interactive session will suck. */
                cpy_log_exception("interactive session init");
        }
        cur_sig = PyOS_setsig(SIGINT, python_sigint_handler);
-       /* We totally forked just now. Everyone saw that, right? */
        PyOS_AfterFork();
+       PyEval_InitThreads();
+       close(*(int *) pipefd);
        PyRun_InteractiveLoop(stdin, "<stdin>");
        PyOS_setsig(SIGINT, cur_sig);
        PyErr_Print();
-       PyEval_ReleaseThread(state);
+       state = PyEval_SaveThread();
        NOTICE("python: Interactive interpreter exited, stopping collectd ...");
        pthread_kill(main_thread, SIGINT);
        return NULL;
@@ -991,6 +1006,8 @@ static void *cpy_interactive(void *data) {
 
 static int cpy_init(void) {
        PyObject *ret;
+       int pipefd[2];
+       char buf;
        static pthread_t thread;
 
        if (!Py_IsInitialized()) {
@@ -999,8 +1016,22 @@ static int cpy_init(void) {
                Py_Finalize();
                return 0;
        }
-       PyEval_InitThreads();
-       /* Now it's finally OK to use python threads. */
+       main_thread = pthread_self();
+       if (do_interactive) {
+               if (pipe(pipefd)) {
+                       ERROR("python: Unable to create pipe.");
+                       return 1;
+               }
+               if (plugin_thread_create(&thread, NULL, cpy_interactive, pipefd + 1)) {
+                       ERROR("python: Error creating thread for interactive interpreter.");
+               }
+               (void)read(pipefd[0], &buf, 1);
+               (void)close(pipefd[0]);
+       } else {
+               PyEval_InitThreads();
+               state = PyEval_SaveThread();
+       }
+       CPY_LOCK_THREADS
        for (cpy_callback_t *c = cpy_init_callbacks; c; c = c->next) {
                ret = PyObject_CallFunctionObjArgs(c->callback, c->data, (void *) 0); /* New reference. */
                if (ret == NULL)
@@ -1008,13 +1039,7 @@ static int cpy_init(void) {
                else
                        Py_DECREF(ret);
        }
-       state = PyEval_SaveThread();
-       main_thread = pthread_self();
-       if (do_interactive) {
-               if (plugin_thread_create(&thread, NULL, cpy_interactive, NULL)) {
-                       ERROR("python: Error creating thread for interactive interpreter.");
-               }
-       }
+       CPY_RELEASE_THREADS
 
        return 0;
 }