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[68.147.0.187]) by smtp.gmail.com with ESMTPSA id t189sm6845630pgt.39.2021.02.25.13.46.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Feb 2021 13:46:58 -0800 (PST) Date: Thu, 25 Feb 2021 14:46:57 -0700 From: Mathieu Poirier To: Mike Leach Cc: linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org, linux-doc@vger.kernel.org, suzuki.poulose@arm.com, yabinc@google.com, corbet@lwn.net, leo.yan@linaro.org, alexander.shishkin@linux.intel.com, tingwei@codeaurora.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 05/10] coresight: syscfg: Add API to activate and enable configurations Message-ID: <20210225214657.GB3567106@xps15> References: <20210128170936.9222-1-mike.leach@linaro.org> <20210128170936.9222-6-mike.leach@linaro.org> <20210225212050.GA3567106@xps15> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210225212050.GA3567106@xps15> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [...] > > + > > +/** > > + * 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 > >