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coresight: configfs: Fix unload of configurations on module exit

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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.

Fixes: eb2ec49606 ("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>
Reviewed-and-tested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220628173004.30002-2-mike.leach@linaro.org
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
This commit is contained in:
Mike Leach 2022-06-28 18:30:03 +01:00 committed by Mathieu Poirier
parent 2af89ebacf
commit 199380decc
1 changed files with 95 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

108
drivers/hwtracing/coresight/coresight-syscfg.c
View File

@ -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,
@ -1022,8 +1043,10 @@ 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. */
@ -1042,6 +1065,13 @@ 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 +1086,73 @@ create_dev_exit_unlock:
return err;
}
/*
* 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_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);
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: prior module failed to unload configuration\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)
{
struct cscfg_config_desc *cfg_desc;
mutex_lock(&cscfg_mutex);
list_for_each_entry(cfg_desc, &cscfg_mgr->config_desc_list, item) {
etm_perf_del_symlink_cscfg(cfg_desc);
}
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 +1160,16 @@ 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)