Subject: module: move find_module check to end From: Linus Torvalds I think Rusty may have made the lock a bit _too_ finegrained there, and didn't add it to some places that needed it. It looks, for example, like PATCH 1/2 actually drops the lock in places where it's needed ("find_module()" is documented to need it, but now load_module() didn't hold it at all when it did the find_module()). Rather than adding a new "module_loading" list, I think we should be able to just use the existing "modules" list, and just fix up the locking a bit. In fact, maybe we could just move the "look up existing module" a bit later - optimistically assuming that the module doesn't exist, and then just undoing the work if it turns out that we were wrong, just before adding ourselves to the list. Signed-off-by: Rusty Russell --- kernel/module.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/kernel/module.c b/kernel/module.c --- a/kernel/module.c +++ b/kernel/module.c @@ -2234,11 +2234,6 @@ static noinline struct module *load_modu 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. */ @@ -2517,6 +2512,12 @@ static noinline struct module *load_modu * 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); @@ -2542,6 +2544,7 @@ static noinline struct module *load_modu 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);