Merged revisions 307623 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

........
  r307623 | rmudgett | 2011-02-10 18:29:17 -0600 (Thu, 10 Feb 2011) | 13 lines

  Reentrancy problem if outgoing call gets different B channel than requested.

  The chan_dahdi pri_fixup_principle() routine needs to protect the Asterisk
  channel with the channel lock when it changes the technology private
  pointer to a new private structure.

  * Added lock protection while pri_fixup_principle() moves a call from one
  private structure to another.

  * Made some pri_fixup_principle() messages more meaningful.

  Partial backport from v1.8 -r300714.
........

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@307624 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_dahdi.c b/channels/chan_dahdi.c
index b681ba9060a48525c6e4a6de736d7a1e7a08e8dd..f7bedbca1fc4f48f0c41a429830f41fe68971925 100644 (file)
--- a/channels/chan_dahdi.c
+++ b/channels/chan_dahdi.c
@@ -12502,6 +12502,51 @@ static struct dahdi_pvt *pri_find_crv(struct dahdi_pri *pri, int crv)
 #endif /* defined(HAVE_PRI) */
 
 #if defined(HAVE_PRI)
+/*!
+ * \internal
+ * \brief Obtain the DAHDI owner channel lock if the owner exists.
+ * \since 1.8
+ *
+ * \param pri DAHDI PRI control structure.
+ * \param chanpos Channel position in the span.
+ *
+ * \note Assumes the pri->lock is already obtained.
+ * \note Assumes the pri->pvts[chanpos]->lock is already obtained.
+ *
+ * \return Nothing
+ */
+static void sig_pri_lock_owner(struct dahdi_pri *pri, int chanpos)
+{
+       for (;;) {
+               if (!pri->pvts[chanpos]->owner) {
+                       /* There is no owner lock to get. */
+                       break;
+               }
+               if (!ast_channel_trylock(pri->pvts[chanpos]->owner)) {
+                       /* We got the lock */
+                       break;
+               }
+               /* We must unlock the PRI to avoid the possibility of a deadlock */
+               ast_mutex_unlock(&pri->lock);
+               DEADLOCK_AVOIDANCE(&pri->pvts[chanpos]->lock);
+               ast_mutex_lock(&pri->lock);
+       }
+}
+#endif /* defined(HAVE_PRI) */
+
+#if defined(HAVE_PRI)
+/*!
+ * \internal
+ * \brief Find the private structure for the libpri call.
+ *
+ * \param pri Span controller structure.
+ * \param channel LibPRI encoded channel ID.
+ *
+ * \note Assumes the pri->lock is already obtained.
+ *
+ * \retval array-index into private pointer array on success.
+ * \retval -1 on error.
+ */
 static int pri_find_principle(struct dahdi_pri *pri, int channel)
 {
        int x;
@@ -12532,6 +12577,19 @@ static int pri_find_principle(struct dahdi_pri *pri, int channel)
 #endif /* defined(HAVE_PRI) */
 
 #if defined(HAVE_PRI)
+/*!
+ * \internal
+ * \brief Fixup the private structure associated with the libpri call.
+ *
+ * \param pri Span controller structure.
+ * \param principle Array-index into private array to move call to if not already there.
+ * \param c LibPRI opaque call pointer to find if need to move call.
+ *
+ * \note Assumes the pri->lock is already obtained.
+ *
+ * \retval principle on success.
+ * \retval -1 on error.
+ */
 static int pri_fixup_principle(struct dahdi_pri *pri, int principle, q931_call *c)
 {
        int x;
@@ -12555,13 +12613,27 @@ static int pri_fixup_principle(struct dahdi_pri *pri, int principle, q931_call *
                        if (principle != x) {
                                struct dahdi_pvt *new = pri->pvts[principle], *old = pri->pvts[x];
 
-                               ast_verb(3, "Moving call from channel %d to channel %d\n",
-                                        old->channel, new->channel);
+                               /* Get locks to safely move to the new private structure. */
+                               ast_mutex_lock(&old->lock);
+                               sig_pri_lock_owner(pri, x);
+                               ast_mutex_lock(&new->lock);
+
+                               ast_verb(3, "Moving call (%s) from channel %d to %d.\n",
+                                       old->owner ? old->owner->name : "",
+                                       old->channel, new->channel);
                                if (new->owner) {
-                                       ast_log(LOG_WARNING, "Can't fix up channel from %d to %d because %d is already in use\n",
-                                               old->channel, new->channel, new->channel);
+                                       ast_log(LOG_WARNING,
+                                               "Can't move call (%s) from channel %d to %d.  It is already in use.\n",
+                                               old->owner ? old->owner->name : "",
+                                               old->channel, new->channel);
+                                       ast_mutex_unlock(&new->lock);
+                                       if (old->owner) {
+                                               ast_channel_unlock(old->owner);
+                                       }
+                                       ast_mutex_unlock(&old->lock);
                                        return -1;
                                }
+
                                /* Fix it all up now */
                                new->owner = old->owner;
                                old->owner = NULL;
@@ -12599,6 +12671,12 @@ static int pri_fixup_principle(struct dahdi_pri *pri, int principle, q931_call *
                                /* More stuff to transfer to the new channel. */
                                new->call_level = old->call_level;
                                old->call_level = DAHDI_CALL_LEVEL_IDLE;
+ 
+                               ast_mutex_unlock(&old->lock);
+                               if (new->owner) {
+                                       ast_channel_unlock(new->owner);
+                               }
+                               ast_mutex_unlock(&new->lock);
                        }
                        return principle;
                }