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authorRusty Russell <rusty@rustcorp.com.au>2012-09-28 14:31:03 +0930
committerRusty Russell <rusty@rustcorp.com.au>2012-09-28 14:31:03 +0930
commit9bb9c3be56834653878f766f471fa1c20e562f4c (patch)
tree5b84043b800db520f551c86f10418e2e2a852cf0
parent6f13909f4fe9652f189b462c6c98767309000321 (diff)
module: wait when loading a module which is currently initializing.
The original module-init-tools module loader used a fnctl lock on the .ko file to avoid attempts to simultaneously load a module. Unfortunately, you can't get an exclusive fcntl lock on a read-only fd, making this not work for read-only mounted filesystems. module-init-tools has a hacky sleep-and-loop for this now. It's not that hard to wait in the kernel, and only return -EEXIST once the first module has finished loading (or continue loading the module if the first one failed to initialize for some reason). It's also consistent with what we do for dependent modules which are still loading. Suggested-by: Lucas De Marchi <lucas.demarchi@profusion.mobi> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
-rw-r--r--kernel/module.c28
1 files changed, 26 insertions, 2 deletions
diff --git a/kernel/module.c b/kernel/module.c
index 63cf6e7f1394..74bc19562ca3 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2845,6 +2845,20 @@ static int post_relocation(struct module *mod, const struct load_info *info)
return module_finalize(info->hdr, info->sechdrs, mod);
}
+/* Is this module of this name done loading? No locks held. */
+static bool finished_loading(const char *name)
+{
+ struct module *mod;
+ bool ret;
+
+ mutex_lock(&module_mutex);
+ mod = find_module(name);
+ ret = !mod || mod->state != MODULE_STATE_COMING;
+ mutex_unlock(&module_mutex);
+
+ return ret;
+}
+
/* Allocate and load the module: note that size of section 0 is always
zero, and we rely on this for optional sections. */
static struct module *load_module(void __user *umod,
@@ -2852,7 +2866,7 @@ static struct module *load_module(void __user *umod,
const char __user *uargs)
{
struct load_info info = { NULL, };
- struct module *mod;
+ struct module *mod, *old;
long err;
pr_debug("load_module: umod=%p, len=%lu, uargs=%p\n",
@@ -2918,8 +2932,18 @@ static struct module *load_module(void __user *umod,
* function to insert in a way safe to concurrent readers.
* The mutex protects against concurrent writers.
*/
+again:
mutex_lock(&module_mutex);
- if (find_module(mod->name)) {
+ if ((old = find_module(mod->name)) != NULL) {
+ if (old->state == MODULE_STATE_COMING) {
+ /* Wait in case it fails to load. */
+ mutex_unlock(&module_mutex);
+ err = wait_event_interruptible(module_wq,
+ finished_loading(mod->name));
+ if (err)
+ goto free_arch_cleanup;
+ goto again;
+ }
err = -EEXIST;
goto unlock;
}