Merged revisions 270867 via svnmerge from

https://origsvn.digium.com/svn/asterisk/trunk

................
  r270867 | dvossel | 2010-06-16 12:36:51 -0500 (Wed, 16 Jun 2010) | 28 lines

  Merged revisions 270866 via svnmerge from
  https://origsvn.digium.com/svn/asterisk/branches/1.4

  ........
    r270866 | dvossel | 2010-06-16 12:35:29 -0500 (Wed, 16 Jun 2010) | 22 lines

    fixes chan_iax2 race condition

    There is code in chan_iax2.c that attempts to guarantee that only a single
    active thread will handle a call number at a time.  This code works once
    the thread is added to an active_list of threads, but we are not currently
    guaranteed that a newly activated thread will enter the active_list immediately
    because it is left up to the thread to add itself after frames have been
    queued to it.  This means that if two frames come in for the same call number
    at the same time, it is possible for them to grab two separate threads because
    the first thread did not add itself to the active_list fast enough.  This
    causes some pretty complex problems.

    This patch resolves this race condition by immediately adding an activated
    thread to the active_list within the network thread and only depending on
    the thread to remove itself once it is done processing the frames queued to
    it.  By doing this we are guaranteed that if another frame for the same call
    number comes in at the same time, that this thread will immediately be found
    in the active_list of threads.

    Review: https://reviewboard.asterisk.org/r/720/
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git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.2@270868 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index 3cf2596fbf4609c55551749faaec646d98e2a83e..6fc1b658098b8149b3bd773bdfe9e6ccb4547f72 100644 (file)
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -9252,6 +9252,7 @@ static int socket_read(int *id, int fd, short events, void *cbdata)
                        memcpy(&thread->ffinfo.sin, &thread->iosin, sizeof(thread->ffinfo.sin));
                        thread->ffinfo.type = fh->type;
                        thread->ffinfo.csub = fh->csub;
+                       AST_LIST_INSERT_HEAD(&active_list, thread, list);
                }
                AST_LIST_UNLOCK(&active_list);
        }
@@ -11215,11 +11216,6 @@ static void *iax2_process_thread(void *data)
                if (thread->iostate == IAX_IOSTATE_IDLE)
                        continue;
 
-               /* Add ourselves to the active list now */
-               AST_LIST_LOCK(&active_list);
-               AST_LIST_INSERT_HEAD(&active_list, thread, list);
-               AST_LIST_UNLOCK(&active_list);
-
                /* See what we need to do */
                switch(thread->iostate) {
                case IAX_IOSTATE_READY:
@@ -11243,7 +11239,9 @@ static void *iax2_process_thread(void *data)
                thread->curfunc[0]='\0';
 #endif         
 
-               /* Now... remove ourselves from the active list, and return to the idle list */
+               /* The network thread added us to the active_thread list when we were given
+                * frames to process, Now that we are done, we must remove ourselves from
+                * the active list, and return to the idle list */
                AST_LIST_LOCK(&active_list);
                AST_LIST_REMOVE(&active_list, thread, list);
                AST_LIST_UNLOCK(&active_list);