Re: [PATCH v4 05/10] coresight: syscfg: Add API to activate and enable configurations
From: Mathieu Poirier
Date: Thu Feb 25 2021 - 16:47:55 EST
[...]
>
> +
>
> +/**
>
> + * Mark a config descriptor as active.
>
> + * This will be seen when csdev devices are activated in the system.
>
> + *
>
> + * Selection by hash value - generated from the configuration name when it
>
> + * was loaded and added to the cs_etm/configurations file system for selection
>
> + * by perf.
>
> + *
>
> + * @cfg_hash: Hash value of the selected configuration name.
>
> + */
>
> +int cscfg_activate_config(unsigned long cfg_hash)
>
> +{
>
> + struct cscfg_config_desc *curr_item, *match_item = 0;
>
> +
>
> + mutex_lock(&cscfg_mutex);
>
> +
>
> + list_for_each_entry(curr_item, &cscfg_mgr->data.config_desc_list, item) {
>
> + if ((unsigned long)curr_item->id_ea->var == cfg_hash) {
>
> + match_item = curr_item;
>
> + atomic_inc(&cscfg_mgr->data.sys_active_cnt);
>
>
It would be nice to have a comment that mentions why this is needed. I had to
>
go look in patch 09 to see that it prevents a feature from being changed when
>
any configuration is active. And since patch 09 is the only place where
>
@sys_active_cnt is used, please move the declaration and handling of the
>
variable there.
>
>
> + break;
>
> + }
>
> + }
>
> + mutex_unlock(&cscfg_mutex);
>
> +
>
> + if (!match_item)
>
> + return -EINVAL;
>
> +
>
> + dev_dbg(to_device_cscfg(), "Activate config %s.\n", match_item->name);
>
> +
>
> + /* mark the descriptors as active so enable config will use them */
>
> + mutex_lock(&cscfg_csdev_mutex);
>
> + atomic_inc(&match_item->active_cnt);
>
>
What is ->active_cnt used for? I see it referenced in
>
cscfg_csdev_enable_active_config() but it doesn't do much other than to confirm
>
the configuration has been activated by someone.
>
>
There is also a chance that a caller would call cscfg_activate_config() once and
>
call cscfg_csdev_enable_active_config() multiple time, which would really create
>
problems. I would move the incrementation of sys_active_cnt within the mutex
>
hold in cscfg_csdev_enable_active_config() and get rid of ->active_cnt. If I am
>
correct we wouldn't need cscfg_activate_config() after that.
>
I looked at patch 06 and I understand why incrementing sys_active_cnt has to be
done before enabling it. If it wasn't so someone could update the feature
between the time setup_aux() is called and the event is installed on a CPU. As
such cscfg_activate_config() should stay but I still think ->active_cnt should
go.
>
> + mutex_unlock(&cscfg_csdev_mutex);
>
> +
>
> + return 0;
>
> +}
>
> +EXPORT_SYMBOL_GPL(cscfg_activate_config);
>
> +
>
> +void cscfg_deactivate_config(unsigned long cfg_hash)
>
>
I'm fine with either cfg_hash or id_hash, but not both.
>
>
> +{
>
> + struct cscfg_config_desc *curr_item, *match_item = 0;
>
> +
>
> + mutex_lock(&cscfg_mutex);
>
> +
>
> + list_for_each_entry(curr_item, &cscfg_mgr->data.config_desc_list, item) {
>
> + if ((unsigned long)curr_item->id_ea->var == cfg_hash) {
>
> + match_item = curr_item;
>
> + break;
>
> + }
>
> + }
>
> + mutex_unlock(&cscfg_mutex);
>
> + if (!match_item)
>
> + return;
>
> +
>
> + dev_dbg(to_device_cscfg(), "Deactivate config %s.\n", match_item->name);
>
> +
>
> + mutex_lock(&cscfg_csdev_mutex);
>
> + atomic_dec(&match_item->active_cnt);
>
> + mutex_unlock(&cscfg_csdev_mutex);
>
> +
>
> + atomic_dec(&cscfg_mgr->data.sys_active_cnt);
>
> +}
>
> +EXPORT_SYMBOL_GPL(cscfg_deactivate_config);
>
> +
>
> +/* Find and program any active config for the supplied device.*/
>
> +int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
>
> + unsigned long id_hash, int preset)
>
> +{
>
> + struct cscfg_config_csdev *cfg = NULL, *item;
>
> + const struct cscfg_config_desc *desc;
>
> + int err = 0;
>
> +
>
> + /* quickly check global count */
>
> + if (!atomic_read(&cscfg_mgr->data.sys_active_cnt))
>
> + return 0;
>
> +
>
> + mutex_lock(&cscfg_csdev_mutex);
>
> + list_for_each_entry(item, &csdev->config_csdev_list, node) {
>
> + desc = item->desc;
>
> + if ((atomic_read(&desc->active_cnt)) &&
>
> + ((unsigned long)desc->id_ea->var == id_hash)) {
>
> + cfg = item;
>
> + break;
>
> + }
>
> + }
>
> + if (cfg) {
>
> + err = cscfg_csdev_enable_config(cfg, preset);
>
> + if (!err)
>
> + csdev->active_cfg_ctxt = (void *)cfg;
>
> + }
>
> + mutex_unlock(&cscfg_csdev_mutex);
>
> + return err;
>
> +}
>
> +EXPORT_SYMBOL_GPL(cscfg_csdev_enable_active_config);
>
> +
>
> +/* save and disable the active config for the device */
>
> +void cscfg_csdev_disable_active_config(struct coresight_device *csdev)
>
> +{
>
> + struct cscfg_config_csdev *cfg;
>
> +
>
> + mutex_lock(&cscfg_csdev_mutex);
>
> + cfg = (struct cscfg_config_csdev *)csdev->active_cfg_ctxt;
>
> + if (cfg)
>
> + cscfg_csdev_disable_config(cfg);
>
> + mutex_unlock(&cscfg_csdev_mutex);
>
> +}
>
> +EXPORT_SYMBOL_GPL(cscfg_csdev_disable_active_config);
>
> +
>
> /* Initialise system configuration management device. */
>
>
>
> struct device *to_device_cscfg(void)
>
> @@ -546,6 +672,7 @@ int __init cscfg_init(void)
>
> INIT_LIST_HEAD(&cscfg_mgr->data.feat_desc_list);
>
> INIT_LIST_HEAD(&cscfg_mgr->data.config_desc_list);
>
> cscfg_mgr->data.nr_csdev = 0;
>
> + atomic_set(&cscfg_mgr->data.sys_active_cnt, 0);
>
>
>
> dev_info(to_device_cscfg(), "CoreSight Configuration manager initialised");
>
> return 0;
>
> diff --git a/drivers/hwtracing/coresight/coresight-syscfg.h b/drivers/hwtracing/coresight/coresight-syscfg.h
>
> index ebf5e1491d86..301e26e1e98f 100644
>
> --- a/drivers/hwtracing/coresight/coresight-syscfg.h
>
> +++ b/drivers/hwtracing/coresight/coresight-syscfg.h
>
> @@ -17,13 +17,15 @@
>
> * @csdev_list: List of coresight devices registered with the configuration manager.
>
> * @feat_desc_list: List of feature descriptors to load into registered devices.
>
> * @config_desc_list: List of system configuration descriptors to load into registered devices.
>
> - * @nr_csdev: Number of registered devices with the cscfg system
>
> + * @nr_csdev: Number of registered devices with the cscfg system
>
> + * @sys_active_cnt: Total number of active config descriptor references.
>
> */
>
> struct cscfg_api_data {
>
> struct list_head csdev_desc_list;
>
> struct list_head feat_desc_list;
>
> struct list_head config_desc_list;
>
> int nr_csdev;
>
> + atomic_t sys_active_cnt;
>
> };
>
>
>
> /**
>
> @@ -53,6 +55,12 @@ int cscfg_register_csdev(struct coresight_device *csdev,
>
> struct cscfg_match_desc *info,
>
> struct cscfg_csdev_feat_ops *ops);
>
> void cscfg_unregister_csdev(struct coresight_device *csdev);
>
> +int cscfg_activate_config(unsigned long cfg_hash);
>
> +void cscfg_deactivate_config(unsigned long cfg_hash);
>
> +void cscfg_csdev_reset_feats(struct coresight_device *csdev);
>
> +int cscfg_csdev_enable_active_config(struct coresight_device *csdev,
>
> + unsigned long id_hash, int preset);
>
> +void cscfg_csdev_disable_active_config(struct coresight_device *csdev);
>
>
>
> /**
>
> * System configuration manager device.
>
> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>
> index d0126ed326a6..3941854e8280 100644
>
> --- a/include/linux/coresight.h
>
> +++ b/include/linux/coresight.h
>
> @@ -221,6 +221,7 @@ struct coresight_sysfs_link {
>
> * @has_conns_grp: Have added a "connections" group for sysfs links.
>
> * @feature_csdev_list: List of complex feature programming added to the device.
>
> * @config_csdev_list: List of system configurations added to the device.
>
> + * @active_cfg_ctxt: Context information for current active congfig.
>
> */
>
> struct coresight_device {
>
> struct coresight_platform_data *pdata;
>
> @@ -245,6 +246,7 @@ struct coresight_device {
>
> /* system configuration and feature lists */
>
> struct list_head feature_csdev_list;
>
> struct list_head config_csdev_list;
>
> + void *active_cfg_ctxt;
>
> };
>
>
>
> /*
>
> --
>
> 2.17.1
>
>