On Wed, Jun 22, 2022 at 11:16:20AM +0100, Mike Leach wrote:
Any loaded configurations must be correctly unloaded on coresight module exit, or issues can arise with nested locking in the configfs directory code if built with CONFIG_LOCKDEP.
Prior to this patch, the preloaded configuration configfs directory entries were being unloaded by the recursive code in configfs_unregister_subsystem().
However, when built with CONFIG_LOCKDEP, this caused a nested lock warning, which was not mitigated by the LOCKDEP dependent code in fs/configfs/dir.c designed to prevent this, due to the different directory levels for the root of the directory being removed.
As the preloaded (and all other) configurations are registered after configfs_register_subsystem(), we now explicitly unload them before the call to configfs_unregister_subsystem().
The new routine cscfg_unload_cfgs_on_exit() iterates through the load owner list to unload any remaining configurations that were not unloaded by the user before the module exits. This covers both the CSCFG_OWNER_PRELOAD and CSCFG_OWNER_MODULE owner types, and will be extended to cover future load owner types for CoreSight configurations.
Applies to coresight/next
The above sentence will end up in the kernel log forever, which is not what we want.
Fixes: eb2ec49606c2 ("coresight: syscfg: Update load API for config loadable modules") Reported-by: Suzuki Poulose suzuki.poulose@arm.com Signed-off-by: Mike Leach mike.leach@linaro.org
.../hwtracing/coresight/coresight-syscfg.c | 106 ++++++++++++++++-- 1 file changed, 95 insertions(+), 11 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c index 11850fd8c3b5..9cd7d3c91d8e 100644 --- a/drivers/hwtracing/coresight/coresight-syscfg.c +++ b/drivers/hwtracing/coresight/coresight-syscfg.c @@ -414,6 +414,27 @@ static void cscfg_remove_owned_csdev_features(struct coresight_device *csdev, vo } } +/*
- Unregister all configuration and features from configfs owned by load_owner.
- Although this is called without the list mutex being held, it is in the
- context of an unload operation which are strictly serialised,
- so the lists cannot change during this call.
- */
+static void cscfg_fs_unregister_cfgs_feats(void *load_owner) +{
- struct cscfg_config_desc *config_desc;
- struct cscfg_feature_desc *feat_desc;
- list_for_each_entry(config_desc, &cscfg_mgr->config_desc_list, item) {
if (config_desc->load_owner == load_owner)cscfg_configfs_del_config(config_desc);- }
- list_for_each_entry(feat_desc, &cscfg_mgr->feat_desc_list, item) {
if (feat_desc->load_owner == load_owner)cscfg_configfs_del_feature(feat_desc);- }
+}
/*
- removal is relatively easy - just remove from all lists, anything that
- matches the owner. Memory for the descriptors will be managed by the owner,
@@ -1022,10 +1043,13 @@ struct device *cscfg_device(void) /* Must have a release function or the kernel will complain on module unload */ static void cscfg_dev_release(struct device *dev) {
- mutex_lock(&cscfg_mutex); kfree(cscfg_mgr); cscfg_mgr = NULL;
- mutex_unlock(&cscfg_mutex);
}
/* a device is needed to "own" some kernel elements such as sysfs entries. */ static int cscfg_create_device(void) { @@ -1042,6 +1066,13 @@ static int cscfg_create_device(void) if (!cscfg_mgr) goto create_dev_exit_unlock;
- /* initialise the cscfg_mgr structure */
- INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list);
- INIT_LIST_HEAD(&cscfg_mgr->feat_desc_list);
- INIT_LIST_HEAD(&cscfg_mgr->config_desc_list);
- INIT_LIST_HEAD(&cscfg_mgr->load_order_list);
- atomic_set(&cscfg_mgr->sys_active_cnt, 0);
- /* setup the device */ dev = cscfg_device(); dev->release = cscfg_dev_release;
@@ -1056,17 +1087,74 @@ static int cscfg_create_device(void) return err; } -static void cscfg_clear_device(void) +/*
- Loading and unloading is generally on user discretion.
- If exiting due to coresight module unload, we need to unload any configurations that remain,
- before we unregister the configfs intrastructure.
- Do this by walking the load_owner list and taking appropriate action, depending on the load
- owner type.
- */
+static void cscfg_unload_cfgs_on_exit(void) {
- struct cscfg_config_desc *cfg_desc;
- struct cscfg_load_owner_info *owner_info = NULL;
- /*
* grab the mutex - even though we are exiting, some configfs files* may still be live till we dump them, so ensure list data is* protected from a race condition.*/
- list_for_each_entry(cfg_desc, &cscfg_mgr->config_desc_list, item) {
etm_perf_del_symlink_cscfg(cfg_desc);
- while (!list_empty(&cscfg_mgr->load_order_list)) {
/* remove in reverse order of loading */owner_info = list_last_entry(&cscfg_mgr->load_order_list,struct cscfg_load_owner_info, item);/* action according to type */switch (owner_info->type) {case CSCFG_OWNER_PRELOAD:/** preloaded descriptors are statically allocated in* this module - just need to unload dynamic items from* csdev lists, and remove from configfs directories.*/pr_info("cscfg: unloading preloaded configurations\n");break;case CSCFG_OWNER_MODULE:/** this is an error - the loadable module must have been unloaded prior* to the coresight module unload. Therefore that module has not* correctly unloaded configs in its own exit code.* Nothing to do other than emit an error string as the static descriptor* references we need to unload will have disappeared with the module.*/pr_err("cscfg: ERROR - a loadable module failed to ""unload configs on exit\n");
This gives me a checkpatch warning. Please correct and resend a new revision.
Thanks, Mathieu
goto list_remove;}/* remove from configfs - outside the scope of the list mutex */mutex_unlock(&cscfg_mutex);cscfg_fs_unregister_cfgs_feats(owner_info);mutex_lock(&cscfg_mutex);/* Next unload from csdev lists. */cscfg_unload_owned_cfgs_feats(owner_info);+list_remove:
/* remove from load order list */list_del(&owner_info->item);- mutex_unlock(&cscfg_mutex);
+}
+static void cscfg_clear_device(void) +{
- cscfg_unload_cfgs_on_exit(); cscfg_configfs_release(cscfg_mgr); device_unregister(cscfg_device());
- mutex_unlock(&cscfg_mutex);
} /* Initialise system config management API device */ @@ -1074,20 +1162,16 @@ int __init cscfg_init(void) { int err = 0;
- /* create the device and init cscfg_mgr */ err = cscfg_create_device(); if (err) return err;
- /* initialise configfs subsystem */ err = cscfg_configfs_init(cscfg_mgr); if (err) goto exit_err;
- INIT_LIST_HEAD(&cscfg_mgr->csdev_desc_list);
- INIT_LIST_HEAD(&cscfg_mgr->feat_desc_list);
- INIT_LIST_HEAD(&cscfg_mgr->config_desc_list);
- INIT_LIST_HEAD(&cscfg_mgr->load_order_list);
- atomic_set(&cscfg_mgr->sys_active_cnt, 0);
- /* preload built-in configurations */ err = cscfg_preload(THIS_MODULE); if (err)
-- 2.17.1