From: Florian Forster <octo@collectd.org>
Date: Sun, 4 Mar 2012 10:10:20 +0000 (+0100)
Subject: perl plugin: Fix a race condition.
X-Git-Tag: collectd-4.10.7~10^2
X-Git-Url: https://git.verplant.org/?a=commitdiff_plain;h=2e48eb524ab27e58d402ef2e88b12d84705cd2b3;p=collectd.git

perl plugin: Fix a race condition.

This hopefully fixes GitHub issue #9.
---

diff --git a/src/perl.c b/src/perl.c
index a2f5da29..41e763dc 100644
--- a/src/perl.c
+++ b/src/perl.c
@@ -1923,6 +1923,11 @@ static int perl_read (void)
 		aTHX = t->interp;
 	}
 
+	/* Assert that we're not running as the base thread. Otherwise, we might
+	 * run into concurrency issues with c_ithread_create(). See
+	 * https://github.com/collectd/collectd/issues/9 for details. */
+	assert (aTHX != perl_threads->head->interp);
+
 	log_debug ("perl_read: c_ithread: interp = %p (active threads: %i)",
 			aTHX, perl_threads->number_of_threads);
 	return pplugin_call_all (aTHX_ PLUGIN_READ);
@@ -1931,6 +1936,7 @@ static int perl_read (void)
 static int perl_write (const data_set_t *ds, const value_list_t *vl,
 		user_data_t __attribute__((unused)) *user_data)
 {
+	int status;
 	dTHX;
 
 	if (NULL == perl_threads)
@@ -1946,9 +1952,20 @@ static int perl_write (const data_set_t *ds, const value_list_t *vl,
 		aTHX = t->interp;
 	}
 
+	/* Lock the base thread if this is not called from one of the read threads
+	 * to avoid race conditions with c_ithread_create(). See
+	 * https://github.com/collectd/collectd/issues/9 for details. */
+	if (aTHX == perl_threads->head->interp)
+		pthread_mutex_lock (&perl_threads->mutex);
+
 	log_debug ("perl_write: c_ithread: interp = %p (active threads: %i)",
 			aTHX, perl_threads->number_of_threads);
-	return pplugin_call_all (aTHX_ PLUGIN_WRITE, ds, vl);
+	status = pplugin_call_all (aTHX_ PLUGIN_WRITE, ds, vl);
+
+	if (aTHX == perl_threads->head->interp)
+		pthread_mutex_unlock (&perl_threads->mutex);
+
+	return status;
 } /* static int perl_write (const data_set_t *, const value_list_t *) */
 
 static void perl_log (int level, const char *msg,
@@ -1969,7 +1986,17 @@ static void perl_log (int level, const char *msg,
 		aTHX = t->interp;
 	}
 
+	/* Lock the base thread if this is not called from one of the read threads
+	 * to avoid race conditions with c_ithread_create(). See
+	 * https://github.com/collectd/collectd/issues/9 for details. */
+	if (aTHX == perl_threads->head->interp)
+		pthread_mutex_lock (&perl_threads->mutex);
+
 	pplugin_call_all (aTHX_ PLUGIN_LOG, level, msg);
+
+	if (aTHX == perl_threads->head->interp)
+		pthread_mutex_unlock (&perl_threads->mutex);
+
 	return;
 } /* static void perl_log (int, const char *) */