Avoid a deadlock with ALL of the locks in the masquerade function, not just the

pairs of channels.  (Closes issue #10406)


git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.4@84049 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 17 insertions, 5 deletions

diff --git a/main/channel.c b/main/channel.c
index 1ffa06416..0ae9af4b0 100644
--- a/main/channel.c
+++ b/main/channel.c
@@ -3410,7 +3410,11 @@ int ast_channel_make_compatible(struct ast_channel *chan, struct ast_channel *pe
 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 @@ int ast_channel_masquerade(struct ast_channel *original, struct ast_channel *clo
 		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);