[PATCH] module unload deadlock fix

From: Rusty Russell <rusty@rustcorp.com.au>

From: Andrea Arcangeli <andrea@suse.de>

We should drop module sem before calling mod->exit, for practical reasons:
too many module exit functions oops or hang, resulting in a permenantly held
module sem, which blocks all module ops including lsmod.

kernel/module.c

@@ -596,7 +596,9 @@ sys_delete_module(const char __user *name_user, unsigned int flags)
 		wait_for_zero_refcount(mod);
 
 	/* Final destruction now noone is using it. */
+	up(&module_mutex);
 	mod->exit();
+	down(&module_mutex);
 	free_module(mod);
 
  out: