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Prevent a potential three-thread deadlock. Also added a comment block

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to explicitly state the locking order necessary inside app_queue.

(closes issue #11862)
Reported by: flujan
Patches:
      11862.patch uploaded by putnopvut (license 60)
	  Tested by: flujan



git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.4@103120 65c4cc65-6c06-0410-ace0-fbb531ad65f3
This commit is contained in:
Mark Michelson
2008-02-08 18:48:17 +00:00
parent 19f5074cd8
commit cb8ffc789e
1 changed files with 22 additions and 7 deletions
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29
apps/app_queue.c
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@@ -99,6 +99,20 @@ ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
#include "asterisk/astobj2.h"
#include "asterisk/global_datastores.h"
/* Please read before modifying this file.
* There are three locks which are regularly used
* throughout this file, the queue list lock, the lock
* for each individual queue, and the interface list lock.
* Please be extra careful to always lock in the following order
* 1) queue list lock
* 2) individual queue lock
* 3) interface list lock
* This order has sort of "evolved" over the lifetime of this
* application, but it is now in place this way, so please adhere
* to this order!
*/
enum {
QUEUE_STRATEGY_RINGALL = 0,
QUEUE_STRATEGY_ROUNDROBIN,
@@ -889,15 +903,16 @@ static int remove_from_interfaces(const char *interface)
{
struct member_interface *curint;
if (interface_exists_global(interface))
return 0;
AST_LIST_LOCK(&interfaces);
AST_LIST_TRAVERSE_SAFE_BEGIN(&interfaces, curint, list) {
if (!strcasecmp(curint->interface, interface)) {
if (!interface_exists_global(interface)) {
if (option_debug)
ast_log(LOG_DEBUG, "Removing %s from the list of interfaces that make up all of our queue members.\n", interface);
AST_LIST_REMOVE_CURRENT(&interfaces, list);
free(curint);
}
if (option_debug)
ast_log(LOG_DEBUG, "Removing %s from the list of interfaces that make up all of our queue members.\n", interface);
AST_LIST_REMOVE_CURRENT(&interfaces, list);
free(curint);
break;
}
}
@@ -4248,9 +4263,9 @@ static int reload_queues(void)
continue;
}
remove_from_interfaces(cur->interface);
q->membercount--;
ao2_unlink(q->members, cur);
remove_from_interfaces(cur->interface);
ao2_ref(cur, -1);
}