[asterisk-commits] tilghman: branch 1.4 r84049 - /branches/1.4/main/channel.c

[SVN commits to the Asterisk project]

Author: tilghman
Date: Fri Sep 28 00:30:22 2007
New Revision: 84049

URL: http://svn.digium.com/view/asterisk?view=rev&rev=84049
Log:
Avoid a deadlock with ALL of the locks in the masquerade function, not just the
pairs of channels.  (Closes issue #10406)

Modified:
    branches/1.4/main/channel.c

Modified: branches/1.4/main/channel.c
URL: http://svn.digium.com/view/asterisk/branches/1.4/main/channel.c?view=diff&rev=84049&r1=84048&r2=84049
==============================================================================
--- branches/1.4/main/channel.c (original)
+++ branches/1.4/main/channel.c Fri Sep 28 00:30:22 2007
@@ -3410,7 +3410,11 @@
 int ast_channel_masquerade(struct ast_channel *original, struct ast_channel *clone)
 {
 	int res = -1;
-	struct ast_channel *final_orig = original, *final_clone = clone;
+	struct ast_channel *final_orig, *final_clone;
+
+retrymasq:
+	final_orig = original;
+	final_clone = clone;
 
 	ast_channel_lock(original);
 	while (ast_channel_trylock(clone)) {
@@ -3428,11 +3432,19 @@
 		final_clone = clone->_bridge;
 
 	if ((final_orig != original) || (final_clone != clone)) {
-		ast_channel_lock(final_orig);
-		while (ast_channel_trylock(final_clone)) {
+		/* Lots and lots of deadlock avoidance.  The main one we're competing with
+		 * is ast_write(), which locks channels recursively, when working with a
+		 * proxy channel. */
+		if (ast_channel_trylock(final_orig)) {
+			ast_channel_unlock(clone);
+			ast_channel_unlock(original);
+			goto retrymasq;
+		}
+		if (ast_channel_trylock(final_clone)) {
 			ast_channel_unlock(final_orig);
-			usleep(1);
-			ast_channel_lock(final_orig);
+			ast_channel_unlock(clone);
+			ast_channel_unlock(original);
+			goto retrymasq;
 		}
 		ast_channel_unlock(clone);
 		ast_channel_unlock(original);