linux-kernel - Re: [PATCH 2/2] module: fix bne2 "gave up waiting for init of module libcrc32c"

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Date:	Tue, 1 Jun 2010 21:35:10 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Brandon Philips <brandon@...p.org>
cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	LKML <linux-kernel@...r.kernel.org>,
	Jon Masters <jonathan@...masters.org>,
	Tejun Heo <htejun@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Kay Sievers <kay.sievers@...y.org>
Subject: Re: [PATCH 2/2] module: fix bne2 "gave up waiting for init of module
 libcrc32c"



On Tue, 1 Jun 2010, Brandon Philips wrote:
> 
> FWIW, I tried this same idea initially and it breaks because the
> kobject EEXIST is coming from mod_sysfs_init() which happens further
> up in load_module() before the list_add_rcu().

Ahh, right. So we'd need to mvoe that down too. As Rusty says, the kobject 
EEXIST warning should be fairly harmless - albeit annoying. Do things 
actually _work_ with that thing apart from the kobject warning?

> I also tried the obvious variation of moving the list_add_rcu() up
> to where the find_module is but got:

Yeah, I don't think moving it up will work, because then the module symbol 
resolver will see itself before having set up the symbols. So I think we 
need to expose it on the modules list only after having done the 
"simplify_symbols()" etc.

I dunno.

Does this work?

(Caveat emptor - I tried to make sure the error cases nest correctly, and 
it all compiles, but it's untested. As usual. Rusty mentioned a "see 
testing patch", but I didn't see it. Maybe he did the same thing)

		Linus
---
 kernel/module.c |   35 +++++++++++++++++++----------------
 1 files changed, 19 insertions(+), 16 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index a1f46a5..247c0aa 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2198,11 +2198,6 @@ static noinline struct module *load_module(void __user *umod,
 		goto free_mod;
 	}
 
-	if (find_module(mod->name)) {
-		err = -EEXIST;
-		goto free_mod;
-	}
-
 	mod->state = MODULE_STATE_COMING;
 
 	/* Allow arches to frob section contents and sizes.  */
@@ -2293,11 +2288,6 @@ static noinline struct module *load_module(void __user *umod,
 	/* Now we've moved module, initialize linked lists, etc. */
 	module_unload_init(mod);
 
-	/* add kobject, so we can reference it. */
-	err = mod_sysfs_init(mod);
-	if (err)
-		goto free_unload;
-
 	/* Set up license info based on the info section */
 	set_license(mod, get_modinfo(sechdrs, infoindex, "license"));
 
@@ -2486,16 +2476,28 @@ static noinline struct module *load_module(void __user *umod,
 	 * The mutex protects against concurrent writers.
 	 */
 	mutex_lock(&module_mutex);
+
+	if (find_module(mod->name)) {
+		err = -EEXIST;
+		/* This will also unlock the mutex */
+		goto already_exists;
+	}
+
 	list_add_rcu(&mod->list, &modules);
 	mutex_unlock(&module_mutex);
 
+	/* add kobject, so we can reference it. */
+	err = mod_sysfs_init(mod);
+	if (err)
+		goto unlink;
+
 	err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp, NULL);
 	if (err < 0)
-		goto unlink;
+		goto sysfs_uninit;
 
 	err = mod_sysfs_setup(mod, mod->kp, mod->num_kp);
 	if (err < 0)
-		goto unlink;
+		goto sysfs_uninit;
 	add_sect_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
 	add_notes_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
 
@@ -2507,18 +2509,19 @@ static noinline struct module *load_module(void __user *umod,
 	/* Done! */
 	return mod;
 
+ sysfs_uninit:
+	free_modinfo(mod);
+	kobject_del(&mod->mkobj.kobj);
+	kobject_put(&mod->mkobj.kobj);
  unlink:
 	mutex_lock(&module_mutex);
 	/* Unlink carefully: kallsyms could be walking list. */
 	list_del_rcu(&mod->list);
+ already_exists:
 	mutex_unlock(&module_mutex);
 	synchronize_sched();
 	module_arch_cleanup(mod);
  cleanup:
-	free_modinfo(mod);
-	kobject_del(&mod->mkobj.kobj);
-	kobject_put(&mod->mkobj.kobj);
- free_unload:
 	module_unload_free(mod);
 #if defined(CONFIG_MODULE_UNLOAD)
 	free_percpu(mod->refptr);
--
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