Author: lstewart
Date: Mon Jun 17 09:49:07 2013
New Revision: 251838
URL: http://svnweb.freebsd.org/changeset/base/251838
Log:
The fix committed in r250951 replaced the reported panic with a deadlock...
gold
star for me. EVENTHANDLER_DEREGISTER() attempts to acquire the lock which is
held by the event handler framework while executing event handler functions,
leading to deadlock.
Move EVENTHANDLER_DEREGISTER() to alq_load_handler() and thus deregister the
ALQ
shutdown_pre_sync handler at module unload time, which takes care of the
originally reported panic and fixes the deadlock introduced in r250951.
Reported by: Luiz Otavio O Souza
MFC after: 3 days
X-MFC with: 250951
Modified:
head/sys/kern/kern_alq.c
Modified: head/sys/kern/kern_alq.c
==============================================================================
--- head/sys/kern/kern_alq.c Mon Jun 17 08:57:09 2013 (r251837)
+++ head/sys/kern/kern_alq.c Mon Jun 17 09:49:07 2013 (r251838)
@@ -229,8 +229,6 @@ ald_shutdown(void *arg, int howto)
{
struct alq *alq;
- EVENTHANDLER_DEREGISTER(shutdown_pre_sync, alq_eventhandler_tag);
-
ALD_LOCK();
/* Ensure no new queues can be created. */
@@ -938,6 +936,8 @@ alq_load_handler(module_t mod, int what,
if (LIST_FIRST(&ald_queues) == NULL) {
ald_shutingdown = 1;
ALD_UNLOCK();
+ EVENTHANDLER_DEREGISTER(shutdown_pre_sync,
+ alq_eventhandler_tag);
ald_shutdown(NULL, 0);
mtx_destroy(&ald_mtx);
} else {
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