Merged revisions 259858 via svnmerge from
authorDavid Vossel <dvossel@digium.com>
Wed, 28 Apr 2010 21:20:03 +0000 (21:20 +0000)
committerDavid Vossel <dvossel@digium.com>
Wed, 28 Apr 2010 21:20:03 +0000 (21:20 +0000)
https://origsvn.digium.com/svn/asterisk/branches/1.4

........
  r259858 | dvossel | 2010-04-28 16:16:03 -0500 (Wed, 28 Apr 2010) | 33 lines

  resolves deadlocks in chan_local

  Issue_1.
  In the local_hangup() 3 locks must be held at the same time... pvt, pvt->chan,
  and pvt->owner.  Proper deadlock avoidance is done when the channel to hangup
  is the outbound chan_local channel, but when it is not the outbound channel we
  have an issue... We attempt to do deadlock avoidance only on the tech pvt, when
  both the tech pvt and the pvt->owner are locked coming into that loop.  By
  never giving up the pvt->owner channel deadlock avoidance is not entirely possible.
  This patch resolves that by doing deadlock avoidance on both the pvt->owner and the pvt
  when trying to get the pvt->chan lock.

  Issue_2.
  ast_prod() is used in ast_activate_generator() to queue a frame on the channel
  and make the channel's read function get called.  This function is used in
  ast_activate_generator() while the channel is locked, which mean's the channel
  will have a lock both from the generator code and the frame_queue code by the
  time it gets to chan_local.c's local_queue_frame code... local_queue_frame
  contains some of the same crazy deadlock avoidance that local_hangup requires,
  and this recursive lock prevents that deadlock avoidance from happening correctly.
  This patch removes ast_prod() from the channel lock so only one lock is held during
  the local_queue_frame function.

  (closes issue #17185)
  Reported by: schmoozecom
  Patches:
        issue_17185_v1.diff uploaded by dvossel (license 671)
        issue_17185_v2.diff uploaded by dvossel (license 671)
  Tested by: schmoozecom, GameGamer43

  Review: https://reviewboard.asterisk.org/r/631/
........

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@259870 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_local.c
main/channel.c

index 7a9bda3..337aadc 100644 (file)
@@ -667,12 +667,12 @@ static int local_hangup(struct ast_channel *ast)
                        /* Deadlock avoidance */
                        while (p->owner && ast_channel_trylock(p->owner)) {
                                ast_mutex_unlock(&p->lock);
-                               if (ast) {
-                                       ast_channel_unlock(ast);
+                               if (p->chan) {
+                                       ast_channel_unlock(p->chan);
                                }
                                usleep(1);
-                               if (ast) {
-                                       ast_channel_lock(ast);
+                               if (p->chan) {
+                                       ast_channel_lock(p->chan);
                                }
                                ast_mutex_lock(&p->lock);
                        }
@@ -687,8 +687,17 @@ static int local_hangup(struct ast_channel *ast)
        } else {
                ast_module_user_remove(p->u_owner);
                while (p->chan && ast_channel_trylock(p->chan)) {
-                       DEADLOCK_AVOIDANCE(&p->lock);
+                               ast_mutex_unlock(&p->lock);
+                               if (p->owner) {
+                                       ast_channel_unlock(p->owner);
+                               }
+                               usleep(1);
+                               if (p->owner) {
+                                       ast_channel_lock(p->owner);
+                               }
+                               ast_mutex_lock(&p->lock);
                }
+
                p->owner = NULL;
                if (p->chan) {
                        ast_queue_hangup(p->chan);
index d958559..ca6cdf8 100644 (file)
@@ -2544,25 +2544,22 @@ int ast_activate_generator(struct ast_channel *chan, struct ast_generator *gen,
        int res = 0;
 
        ast_channel_lock(chan);
-
        if (chan->generatordata) {
                if (chan->generator && chan->generator->release)
                        chan->generator->release(chan, chan->generatordata);
                chan->generatordata = NULL;
        }
-
-       ast_prod(chan);
        if (gen->alloc && !(chan->generatordata = gen->alloc(chan, params))) {
                res = -1;
        }
-       
        if (!res) {
                ast_settimeout(chan, 50, generator_force, chan);
                chan->generator = gen;
        }
-
        ast_channel_unlock(chan);
 
+       ast_prod(chan);
+
        return res;
 }