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module: put modules in list much earlier.

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Prarit's excellent bug report:
> In recent Fedora releases (F17 & F18) some users have reported seeing
> messages similar to
>
> [   15.478160] kvm: Could not allocate 304 bytes percpu data
> [   15.478174] PERCPU: allocation failed, size=304 align=32, alloc from
> reserved chunk failed
>
> during system boot.  In some cases, users have also reported seeing this
> message along with a failed load of other modules.
>
> What is happening is systemd is loading an instance of the kvm module for
> each cpu found (see commit e9bda3b).  When the module load occurs the kernel
> currently allocates the modules percpu data area prior to checking to see
> if the module is already loaded or is in the process of being loaded.  If
> the module is already loaded, or finishes load, the module loading code
> releases the current instance's module's percpu data.

Now we have a new state MODULE_STATE_UNFORMED, we can insert the
module into the list (and thus guarantee its uniqueness) before we
allocate the per-cpu region.

Reported-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Tested-by: Prarit Bhargava <prarit@redhat.com>
This commit is contained in:
Rusty Russell 2013-01-12 13:27:34 +10:30
parent 0d21b0e347
commit 1fb9341ac3
2 changed files with 50 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

90
kernel/module.c
View File

@ -3017,7 +3017,7 @@ static bool finished_loading(const char *name)
bool ret;
mutex_lock(&module_mutex);
mod = find_module(name);
mod = find_module_all(name, true);
ret = !mod || mod->state == MODULE_STATE_LIVE
|| mod->state == MODULE_STATE_GOING;
mutex_unlock(&module_mutex);
@ -3141,6 +3141,32 @@ static int load_module(struct load_info *info, const char __user *uargs,
goto free_copy;
}
/*
* We try to place it in the list now to make sure it's unique
* before we dedicate too many resources. In particular,
* temporary percpu memory exhaustion.
*/
mod->state = MODULE_STATE_UNFORMED;
again:
mutex_lock(&module_mutex);
if ((old = find_module_all(mod->name, true)) != NULL) {
if (old->state == MODULE_STATE_COMING
|| old->state == MODULE_STATE_UNFORMED) {
/* 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_module;
goto again;
}
err = -EEXIST;
mutex_unlock(&module_mutex);
goto free_module;
}
list_add_rcu(&mod->list, &modules);
mutex_unlock(&module_mutex);
#ifdef CONFIG_MODULE_SIG
mod->sig_ok = info->sig_ok;
if (!mod->sig_ok)
@ -3150,7 +3176,7 @@ static int load_module(struct load_info *info, const char __user *uargs,
/* Now module is in final location, initialize linked lists, etc. */
err = module_unload_init(mod);
if (err)
goto free_module;
goto unlink_mod;
/* Now we've got everything in the final locations, we can
* find optional sections. */
@ -3185,54 +3211,33 @@ static int load_module(struct load_info *info, const char __user *uargs,
goto free_arch_cleanup;
}
/* Mark state as coming so strong_try_module_get() ignores us. */
mod->state = MODULE_STATE_COMING;
/* Now sew it into the lists so we can get lockdep and oops
* info during argument parsing. No one should access us, since
* strong_try_module_get() will fail.
* lockdep/oops can run asynchronous, so use the RCU list insertion
* function to insert in a way safe to concurrent readers.
* The mutex protects against concurrent writers.
*/
again:
mutex_lock(&module_mutex);
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;
}
/* This has to be done once we're sure module name is unique. */
dynamic_debug_setup(info->debug, info->num_debug);
/* Find duplicate symbols */
mutex_lock(&module_mutex);
/* Find duplicate symbols (must be called under lock). */
err = verify_export_symbols(mod);
if (err < 0)
goto ddebug;
goto ddebug_cleanup;
/* This relies on module_mutex for list integrity. */
module_bug_finalize(info->hdr, info->sechdrs, mod);
list_add_rcu(&mod->list, &modules);
/* Mark state as coming so strong_try_module_get() ignores us,
* but kallsyms etc. can see us. */
mod->state = MODULE_STATE_COMING;
mutex_unlock(&module_mutex);
/* Module is ready to execute: parsing args may do that. */
err = parse_args(mod->name, mod->args, mod->kp, mod->num_kp,
-32768, 32767, &ddebug_dyndbg_module_param_cb);
if (err < 0)
goto unlink;
goto bug_cleanup;
/* Link in to syfs. */
err = mod_sysfs_setup(mod, info, mod->kp, mod->num_kp);
if (err < 0)
goto unlink;
goto bug_cleanup;
/* Get rid of temporary copy. */
free_copy(info);
@ -3242,16 +3247,13 @@ static int load_module(struct load_info *info, const char __user *uargs,
return do_init_module(mod);
unlink:
bug_cleanup:
/* module_bug_cleanup needs module_mutex protection */
mutex_lock(&module_mutex);
/* 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:
mutex_unlock(&module_mutex);
ddebug_cleanup:
dynamic_debug_remove(info->debug);
synchronize_sched();
kfree(mod->args);
free_arch_cleanup:
@ -3260,6 +3262,12 @@ static int load_module(struct load_info *info, const char __user *uargs,
free_modinfo(mod);
free_unload:
module_unload_free(mod);
unlink_mod:
mutex_lock(&module_mutex);
/* Unlink carefully: kallsyms could be walking list. */
list_del_rcu(&mod->list);
wake_up_all(&module_wq);
mutex_unlock(&module_mutex);
free_module:
module_deallocate(mod, info);
free_copy:

1
lib/bug.c
View File

@ -55,6 +55,7 @@ static inline unsigned long bug_addr(const struct bug_entry *bug)
}
#ifdef CONFIG_MODULES
/* Updates are protected by module mutex */
static LIST_HEAD(module_bug_list);
static const struct bug_entry *module_find_bug(unsigned long bugaddr)