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Message-ID: <CAJ9a7Vj=WGPM3t2HtfrS-o=+9rntL90E=++8Gsxk1W8Aj=nggQ@mail.gmail.com>
Date: Thu, 4 Mar 2021 18:15:13 +0000
From: Mike Leach <mike.leach@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>
Cc: linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
Coresight ML <coresight@...ts.linaro.org>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
Yabin Cui <yabinc@...gle.com>,
Jonathan Corbet <corbet@....net>, Leo Yan <leo.yan@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Tingwei Zhang <tingwei@...eaurora.org>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 05/10] coresight: syscfg: Add API to activate and
enable configurations
Hi Suzuki,
On Thu, 4 Mar 2021 at 16:49, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>
> On 1/28/21 5:09 PM, Mike Leach wrote:
> > Configurations are first activated, then when any coresight device is
> > enabled, the active configurations are checked and any matching
> > one is enabled.
> >
> > This patch provides the activation / enable API.
> >
> > Signed-off-by: Mike Leach <mike.leach@...aro.org>
> > ---
> > .../hwtracing/coresight/coresight-config.h | 2 +
> > .../hwtracing/coresight/coresight-syscfg.c | 127 ++++++++++++++++++
> > .../hwtracing/coresight/coresight-syscfg.h | 10 +-
> > include/linux/coresight.h | 2 +
> > 4 files changed, 140 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h
> > index 98380b496046..26396b70c826 100644
> > --- a/drivers/hwtracing/coresight/coresight-config.h
> > +++ b/drivers/hwtracing/coresight/coresight-config.h
> > @@ -156,6 +156,7 @@ struct cscfg_config_feat_ref {
> > * @presets: Array of preset values.
> > * @id_ea: Extended attribute for perf configid value
> > * @event_ea: Extended attribute for perf event value
> > + * @active_cnt: ref count for activate on this configuration.
> > */
> > struct cscfg_config_desc {
> > const char *name;
> > @@ -168,6 +169,7 @@ struct cscfg_config_desc {
> > const u64 *presets; /* nr_presets * nr_total_params */
> > struct dev_ext_attribute *id_ea;
> > struct dev_ext_attribute *event_ea;
> > + atomic_t active_cnt;
> > };
> >
> > /**
> > diff --git a/drivers/hwtracing/coresight/coresight-syscfg.c b/drivers/hwtracing/coresight/coresight-syscfg.c
> > index a070f135eca3..d79cf5b36758 100644
> > --- a/drivers/hwtracing/coresight/coresight-syscfg.c
> > +++ b/drivers/hwtracing/coresight/coresight-syscfg.c
> > @@ -298,6 +298,7 @@ static int cscfg_load_config(struct cscfg_config_desc *cfg_desc)
> > return err;
> >
> > list_add(&cfg_desc->item, &cscfg_mgr->data.config_desc_list);
> > + atomic_set(&cfg_desc->active_cnt, 0);
> > return 0;
> > }
> >
> > @@ -477,6 +478,131 @@ void cscfg_unregister_csdev(struct coresight_device *csdev)
> > }
> > EXPORT_SYMBOL_GPL(cscfg_unregister_csdev);
> >
> > +void cscfg_csdev_reset_feats(struct coresight_device *csdev)
> > +{
> > + struct cscfg_feature_csdev *feat;
> > +
> > + mutex_lock(&cscfg_csdev_mutex);
> > + if (list_empty(&csdev->feature_csdev_list))
> > + goto unlock_exit;
> > +
> > + list_for_each_entry(feat, &csdev->feature_csdev_list, node)
> > + cscfg_reset_feat(feat);
> > +
> > +unlock_exit:
> > + mutex_unlock(&cscfg_csdev_mutex);
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_csdev_reset_feats);
> > +
> > +/**
> > + * 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;
>
> nit: s/0/NULL
>
OK.
> > +
> > + 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);
> > + 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);
> > + mutex_unlock(&cscfg_csdev_mutex);
>
> Is there a guarantee that this item is active and present in the list after
> we dropped the mutex above ? We could certainly nest the mutex as long as
> we follow the order everywhere to prevent such a race.
>
Although removal not supported in this set, the rule is that nothing
can be removed while any configuration is active (count on
sys_active_cnt). - but a comment here could be added.
That said, given this is an atomic, not sure that the mutex is
necessary (I think previous versions did more than just update the
count), & perhaps the increment should be moved to the main
list_for_each loop.
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(cscfg_activate_config);
> > +
> > +void cscfg_deactivate_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;
> > + 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.
>
> nit: Is this aligned ? (It is from Patch 1, though).
>
> > * @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
>
> Spurious change ?
>
This struct disappears in the v5 respin, so the comments will too.
> > + * @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;
> > };
> >
>
> Suzuki
>
Thanks for the review.
Mike
--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK
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