current/SOURCES/kernel-module-fix-symbol-waiting-when-module-fails-before-i.patch

From 6f13909f4fe9652f189b462c6c98767309000321 Mon Sep 17 00:00:00 2001
From: Rusty Russell <rusty@rustcorp.com.au>
Date: Fri, 28 Sep 2012 14:31:03 +0930
Subject: [PATCH] module: fix symbol waiting when module fails before init

We use resolve_symbol_wait(), which blocks if the module containing
the symbol is still loading.  However:

1) The module_wq we use is only woken after calling the modules' init
   function, but there are other failure paths after the module is
   placed in the linked list where we need to do the same thing.

2) wake_up() only wakes one waiter, and our waitqueue is shared by all
   modules, so we need to wake them all.

3) wake_up_all() doesn't imply a memory barrier: I feel happier calling
   it after we've grabbed and dropped the module_mutex, not just after
   the state assignment.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 kernel/module.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 7f2ee45f..63cf6e7 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2959,7 +2959,7 @@ static struct module *load_module(void __user *umod,
        /* Unlink carefully: kallsyms could be walking list. */
        list_del_rcu(&mod->list);
        module_bug_cleanup(mod);
-
+       wake_up_all(&module_wq);
  ddebug:
        dynamic_debug_remove(info.debug);
  unlock:
@@ -3034,7 +3034,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
                blocking_notifier_call_chain(&module_notify_list,
                                             MODULE_STATE_GOING, mod);
                free_module(mod);
-               wake_up(&module_wq);
+               wake_up_all(&module_wq);
                return ret;
        }
        if (ret > 0) {
@@ -3046,9 +3046,8 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
                dump_stack();
        }
 
-       /* Now it's a first class citizen!  Wake up anyone waiting for it. */
+       /* Now it's a first class citizen! */
        mod->state = MODULE_STATE_LIVE;
-       wake_up(&module_wq);
        blocking_notifier_call_chain(&module_notify_list,
                                     MODULE_STATE_LIVE, mod);
 
@@ -3071,6 +3070,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
        mod->init_ro_size = 0;
        mod->init_text_size = 0;
        mutex_unlock(&module_mutex);
+       wake_up_all(&module_wq);
 
        return 0;
 }
-- 
1.7.12.4

1	From 6f13909f4fe9652f189b462c6c98767309000321 Mon Sep 17 00:00:00 2001
2	From: Rusty Russell <rusty@rustcorp.com.au>
3	Date: Fri, 28 Sep 2012 14:31:03 +0930
4	Subject: [PATCH] module: fix symbol waiting when module fails before init
5
6	We use resolve_symbol_wait(), which blocks if the module containing
7	the symbol is still loading. However:
8
9	1) The module_wq we use is only woken after calling the modules' init
10	function, but there are other failure paths after the module is
11	placed in the linked list where we need to do the same thing.
12
13	2) wake_up() only wakes one waiter, and our waitqueue is shared by all
14	modules, so we need to wake them all.
15
16	3) wake_up_all() doesn't imply a memory barrier: I feel happier calling
17	it after we've grabbed and dropped the module_mutex, not just after
18	the state assignment.
19
20	Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
21	---
22	kernel/module.c \| 8 ++++----
23	1 file changed, 4 insertions(+), 4 deletions(-)
24
25	diff --git a/kernel/module.c b/kernel/module.c
26	index 7f2ee45f..63cf6e7 100644
27	--- a/kernel/module.c
28	+++ b/kernel/module.c
29	@@ -2959,7 +2959,7 @@ static struct module load_module(void __user umod,
30	/* Unlink carefully: kallsyms could be walking list. */
31	list_del_rcu(&mod->list);
32	module_bug_cleanup(mod);
33	-
34	+ wake_up_all(&module_wq);
35	ddebug:
36	dynamic_debug_remove(info.debug);
37	unlock:
38	@@ -3034,7 +3034,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
39	blocking_notifier_call_chain(&module_notify_list,
40	MODULE_STATE_GOING, mod);
41	free_module(mod);
42	- wake_up(&module_wq);
43	+ wake_up_all(&module_wq);
44	return ret;
45	}
46	if (ret > 0) {
47	@@ -3046,9 +3046,8 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
48	dump_stack();
49	}
50
51	- /* Now it's a first class citizen! Wake up anyone waiting for it. */
52	+ /* Now it's a first class citizen! */
53	mod->state = MODULE_STATE_LIVE;
54	- wake_up(&module_wq);
55	blocking_notifier_call_chain(&module_notify_list,
56	MODULE_STATE_LIVE, mod);
57
58	@@ -3071,6 +3070,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod,
59	mod->init_ro_size = 0;
60	mod->init_text_size = 0;
61	mutex_unlock(&module_mutex);
62	+ wake_up_all(&module_wq);
63
64	return 0;
65	}
66	--
67	1.7.12.4
68