perl plugin: Shut down an ithread if the embedding pthread terminates.

Each ithread object is registered as thread specific data along with a
destructor function. If the embedding pthread terminates the destructor is
called which takes care of cleanly shutting down the appropriate Perl
interpreter and freeing any related resources.

diff --git a/src/perl.c b/src/perl.c
index 5cec1ed..b289fa0 100644 (file)
--- a/src/perl.c
+++ b/src/perl.c
@@ -112,6 +112,9 @@ typedef struct {
  * point to the "base" thread */
 static c_ithread_list_t *perl_threads = NULL;
 
+/* the key used to store each pthread's ithread */
+static pthread_key_t perl_thr_key;
+
 static int    perl_argc = 0;
 static char **perl_argv = NULL;
 
@@ -776,6 +779,63 @@ static XS (Collectd_call_by_name)
  */
 
 /* must be called with perl_threads->mutex locked */
+static void c_ithread_destroy (c_ithread_t *ithread)
+{
+       dTHXa (ithread->interp);
+
+       assert (NULL != perl_threads);
+
+       PERL_SET_CONTEXT (aTHX);
+       log_debug ("Shutting down Perl interpreter %p...", aTHX);
+
+#if COLLECT_DEBUG
+       sv_report_used ();
+
+       --perl_threads->number_of_threads;
+#endif /* COLLECT_DEBUG */
+
+       perl_destruct (aTHX);
+       perl_free (aTHX);
+
+       if (NULL == ithread->prev)
+               perl_threads->head = ithread->next;
+       else
+               ithread->prev->next = ithread->next;
+
+       if (NULL == ithread->next)
+               perl_threads->tail = ithread->prev;
+       else
+               ithread->next->prev = ithread->prev;
+
+       sfree (ithread);
+       return;
+} /* static void c_ithread_destroy (c_ithread_t *) */
+
+static void c_ithread_destructor (void *arg)
+{
+       c_ithread_t *ithread = (c_ithread_t *)arg;
+       c_ithread_t *t = NULL;
+
+       if (NULL == perl_threads)
+               return;
+
+       pthread_mutex_lock (&perl_threads->mutex);
+
+       for (t = perl_threads->head; NULL != t; t = t->next)
+               if (t == ithread)
+                       break;
+
+       /* the ithread no longer exists */
+       if (NULL == t)
+               return;
+
+       c_ithread_destroy (ithread);
+
+       pthread_mutex_unlock (&perl_threads->mutex);
+       return;
+} /* static void c_ithread_destructor (void *) */
+
+/* must be called with perl_threads->mutex locked */
 static c_ithread_t *c_ithread_create (PerlInterpreter *base)
 {
        c_ithread_t *t = NULL;
@@ -814,6 +874,8 @@ static c_ithread_t *c_ithread_create (PerlInterpreter *base)
        }
 
        perl_threads->tail = t;
+
+       pthread_setspecific (perl_thr_key, (const void *)t);
        return t;
 } /* static c_ithread_t *c_ithread_create (PerlInterpreter *) */
 
@@ -945,30 +1007,22 @@ static int perl_shutdown (void)
        t = perl_threads->tail;
 
        while (NULL != t) {
-               c_ithread_t *last = NULL;
+               c_ithread_t *thr = t;
 
-               aTHX = t->interp;
-               PERL_SET_CONTEXT (aTHX);
-
-               log_debug ("Shutting down Perl interpreter %p...", aTHX);
-
-#if COLLECT_DEBUG
-               sv_report_used ();
-#endif /* COLLECT_DEBUG */
-
-               perl_destruct (aTHX);
-               perl_free (aTHX);
-
-               last = t;
+               /* the pointer has to be advanced before destroying
+                * the thread as this will free the memory */
                t = t->prev;
 
-               sfree (last);
+               c_ithread_destroy (thr);
        }
 
        pthread_mutex_unlock (&perl_threads->mutex);
+       pthread_mutex_destroy (&perl_threads->mutex);
 
        sfree (perl_threads);
 
+       pthread_key_delete (perl_thr_key);
+
        PERL_SYS_TERM ();
 
        plugin_unregister_shutdown ("perl");
@@ -1018,6 +1072,13 @@ static int init_pi (int argc, char **argv)
        }
 #endif /* COLLECT_DEBUG */
 
+       if (0 != pthread_key_create (&perl_thr_key, c_ithread_destructor)) {
+               log_err ("init_pi: pthread_key_create failed");
+
+               /* this must not happen - cowardly giving up if it does */
+               exit (1);
+       }
+
        PERL_SYS_INIT3 (&argc, &argv, &environ);
 
        perl_threads = (c_ithread_list_t *)smalloc (sizeof (c_ithread_list_t));