Safely handle AMI connections/reload requests that occur during startup.

During asterisk startup, a lock on the list of modules is obtained by the
primary thread while each module is initialized.  Issue 13778 pointed out a
problem with this approach, however.  Because the AMI is loaded before other
modules, it is possible for a module reload to be issued by a connected client
(via Action: Command), causing a deadlock.

The resolution for 13778 was to move initialization of the manager to happen
after the other modules had already been lodaded.  While this fixed this
particular issue, it caused a problem for users (like FreePBX) who call AMI
scripts via an #exec in a configuration file (See issue 15189).

The solution I have come up with is to defer any reload requests that come in
until after the server is fully booted.  When a call comes in to
ast_module_reload (from wherever) before we are fully booted, the request is
added to a queue of pending requests.  Once we are done booting up, we then
execute these deferred requests in turn.

Note that I have tried to make this a bit more intelligent in that it will not
queue up more than 1 request for the same module to be reloaded, and if a
general reload request comes in ('module reload') the queue is flushed and we
only issue a single deferred reload for the entire system.

As for how this will impact existing installations - Before 13778, a reload
issued before module initialization was completed would result in a deadlock.
After 13778, you simply couldn't connect to the manager during startup (which
causes problems with #exec-that-calls-AMI configuration files).  I believe this
is a good general purpose solution that won't negatively impact existing
installations.

(closes issue #15189)
(closes issue #13778)
Reported by: p_lindheimer
Patches:
      06032009_15189_deferred_reloads.diff uploaded by seanbright (license 71)
Tested by: p_lindheimer, seanbright

Review: https://reviewboard.asterisk.org/r/272/


git-svn-id: http://svn.digium.com/svn/asterisk/branches/1.4@199022 f38db490-d61c-443f-a65b-d21fe96a405b

1 files changed, 12 insertions, 0 deletions

diff --git a/include/asterisk.h b/include/asterisk.h
index a827a23f0..41e98f022 100644
--- a/include/asterisk.h
+++ b/include/asterisk.h
@@ -126,6 +126,18 @@ struct ast_module;
 int ast_module_reload(const char *name);
 
 /*!
+ * \brief Process reload requests received during startup.
+ *
+ * This function requests that the loader execute the pending reload requests
+ * that were queued during server startup.
+ *
+ * \note This function will do nothing if the server has not completely started
+ *       up.  Once called, the reload queue is emptied, and further invocations
+ *       will have no affect.
+ */
+void ast_process_pending_reloads(void);
+
+/*!
  * \brief Register a function to be executed before Asterisk exits.
  * \param func The callback function to use.
  *