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
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. + */ mutex_lock(&cscfg_mutex); - 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"); + 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)