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Message-ID: <61bb4e6d-5451-2f01-19b2-76c396854c23@arm.com>
Date: Tue, 4 Apr 2023 13:55:22 +0100
From: James Clark <james.clark@....com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
coresight@...ts.linaro.org, quic_jinlmao@...cinc.com,
mike.leach@...aro.org
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>,
Leo Yan <leo.yan@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-stm32@...md-mailman.stormreply.com
Subject: Re: [PATCH v3 13/13] coresight: Fix CTI module refcount leak by
making it a helper device
On 04/04/2023 10:21, Suzuki K Poulose wrote:
> On 29/03/2023 12:53, James Clark wrote:
>> The CTI module has some hard coded refcounting code that has a leak.
>> For example running perf and then trying to unload it fails:
>>
>> perf record -e cs_etm// -a -- ls
>> rmmod coresight_cti
>>
>> rmmod: ERROR: Module coresight_cti is in use
>>
>> The coresight core already handles references of devices in use, so by
>> making CTI a normal helper device, we get working refcounting for free.
>>
>> Signed-off-by: James Clark <james.clark@....com>
>> ---
>> drivers/hwtracing/coresight/coresight-core.c | 99 ++++++-------------
>> .../hwtracing/coresight/coresight-cti-core.c | 52 +++++-----
>> .../hwtracing/coresight/coresight-cti-sysfs.c | 4 +-
>> drivers/hwtracing/coresight/coresight-cti.h | 4 +-
>> drivers/hwtracing/coresight/coresight-priv.h | 4 +-
>> drivers/hwtracing/coresight/coresight-sysfs.c | 4 +
>> include/linux/coresight.h | 30 +-----
>> 7 files changed, 70 insertions(+), 127 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c
>> b/drivers/hwtracing/coresight/coresight-core.c
>> index 65f5bd8516d8..458d91b4e23f 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -254,60 +254,39 @@ void coresight_disclaim_device(struct
>> coresight_device *csdev)
>> }
>> EXPORT_SYMBOL_GPL(coresight_disclaim_device);
>> -/* enable or disable an associated CTI device of the supplied CS
>> device */
>> -static int
>> -coresight_control_assoc_ectdev(struct coresight_device *csdev, bool
>> enable)
>> -{
>> - int ect_ret = 0;
>> - struct coresight_device *ect_csdev = csdev->ect_dev;
>> - struct module *mod;
>> -
>> - if (!ect_csdev)
>> - return 0;
>> - if ((!ect_ops(ect_csdev)->enable) || (!ect_ops(ect_csdev)->disable))
>> - return 0;
>> -
>> - mod = ect_csdev->dev.parent->driver->owner;
>> - if (enable) {
>> - if (try_module_get(mod)) {
>> - ect_ret = ect_ops(ect_csdev)->enable(ect_csdev);
>> - if (ect_ret) {
>> - module_put(mod);
>> - } else {
>> - get_device(ect_csdev->dev.parent);
>> - csdev->ect_enabled = true;
>> - }
>> - } else
>> - ect_ret = -ENODEV;
>> - } else {
>> - if (csdev->ect_enabled) {
>> - ect_ret = ect_ops(ect_csdev)->disable(ect_csdev);
>> - put_device(ect_csdev->dev.parent);
>> - module_put(mod);
>> - csdev->ect_enabled = false;
>> - }
>> - }
>> -
>> - /* output warning if ECT enable is preventing trace operation */
>> - if (ect_ret)
>> - dev_info(&csdev->dev, "Associated ECT device (%s) %s failed\n",
>> - dev_name(&ect_csdev->dev),
>> - enable ? "enable" : "disable");
>> - return ect_ret;
>> -}
>> -
>> /*
>> - * Set the associated ect / cti device while holding the coresight_mutex
>> + * Add a helper as an output device while holding the coresight_mutex
>> * to avoid a race with coresight_enable that may try to use this
>> value.
>> */
>> -void coresight_set_assoc_ectdev_mutex(struct coresight_device *csdev,
>> - struct coresight_device *ect_csdev)
>> +void coresight_add_helper_mutex(struct coresight_device *csdev,
>> + struct coresight_device *helper)
>
> minor nit: It may be a good idea to rename this, in line with the
> kernel naming convention :
>
> coresight_add_helper_unlocked()
>
> Or if this is the only variant, it is OK to leave it as :
> coresight_add_helper()
> with a big fat comment in the function description to indicate
> that it takes the mutex and may be even add a :
>
There is already a bit of a comment in the description but I can expand
on it more.
> might_sleep() and lockdep_assert_not_held(&coresight_mutex);
>
> in the function.
>
I'm not sure if lockdep_assert_not_held() would be right because
sometimes it could be held if another device is being created at the
same time? Or something like a session is started at the same time a CTI
device is added.
>> {
>> + int i;
>> + struct coresight_connection conn = {};
>> +
>> mutex_lock(&coresight_mutex);
>> - csdev->ect_dev = ect_csdev;
>> + conn.dest_fwnode = fwnode_handle_get(dev_fwnode(&helper->dev));
>> + conn.dest_dev = helper;
>> + conn.dest_port = conn.src_port = -1;
>> + conn.src_dev = csdev;
>> +
>> + /*
>> + * Check for duplicates because this is called every time a helper
>> + * device is re-loaded. Existing connections will get re-linked
>> + * automatically.
>> + */
>
> Thanks for adding this comment here. It does look like the already added
> output connection to the "origin" device would automatically resolve the
> connection and add in the "in-connection" to the CTI device.
>
>> + for (i = 0; i < csdev->pdata->nr_outconns; ++i)
>> + if (csdev->pdata->out_conns[i]->dest_fwnode == conn.dest_fwnode)
>> + goto unlock;
>> +
>> + coresight_add_out_conn(csdev->dev.parent, csdev->pdata, &conn);
>
> This makes me wonder if we should return the new connection in
> coresight_add_out_conn() in case of success, rather than assuming the
> last one (which is always the case though.).
>
> i.e.,
> new_conn = coresight_add_out_conn(...)
> if (new_conn)
> coresight_add_in_conn(new_conn);
>
Yeah I thought about doing that too, will change it.
>> + coresight_add_in_conn(
>> + csdev->pdata->out_conns[csdev->pdata->nr_outconns - 1]);
>> +
>> +unlock:
>> mutex_unlock(&coresight_mutex);
>> }
>> -EXPORT_SYMBOL_GPL(coresight_set_assoc_ectdev_mutex);
>> +EXPORT_SYMBOL_GPL(coresight_add_helper_mutex);
>> static int coresight_enable_sink(struct coresight_device *csdev,
>> enum cs_mode mode, void *data)
>> @@ -321,12 +300,8 @@ static int coresight_enable_sink(struct
>> coresight_device *csdev,
>> if (!sink_ops(csdev)->enable)
>> return -EINVAL;
>> - ret = coresight_control_assoc_ectdev(csdev, true);
>> - if (ret)
>> - return ret;
>> ret = sink_ops(csdev)->enable(csdev, mode, data);
>> if (ret) {
>> - coresight_control_assoc_ectdev(csdev, false);
>> return ret;
>> }
>> csdev->enable = true;
>> @@ -344,7 +319,6 @@ static void coresight_disable_sink(struct
>> coresight_device *csdev)
>> ret = sink_ops(csdev)->disable(csdev);
>> if (ret)
>> return;
>> - coresight_control_assoc_ectdev(csdev, false);
>> csdev->enable = false;
>> }
>> @@ -369,17 +343,11 @@ static int coresight_enable_link(struct
>> coresight_device *csdev,
>> return PTR_ERR(outconn);
>> if (link_ops(csdev)->enable) {
>> - ret = coresight_control_assoc_ectdev(csdev, true);
>> - if (!ret) {
>> - ret = link_ops(csdev)->enable(csdev, inconn, outconn);
>> - if (ret)
>> - coresight_control_assoc_ectdev(csdev, false);
>> - }
>> + ret = link_ops(csdev)->enable(csdev, inconn, outconn);
>> + if (!ret)
>> + csdev->enable = true;
>> }
>> - if (!ret)
>> - csdev->enable = true;
>> -
>> return ret;
>> }
>> @@ -400,7 +368,6 @@ static void coresight_disable_link(struct
>> coresight_device *csdev,
>> if (link_ops(csdev)->disable) {
>> link_ops(csdev)->disable(csdev, inconn, outconn);
>> - coresight_control_assoc_ectdev(csdev, false);
>> }
>> if (link_subtype == CORESIGHT_DEV_SUBTYPE_LINK_MERG) {
>> @@ -428,14 +395,9 @@ int coresight_enable_source(struct
>> coresight_device *csdev, void *data,
>> if (!csdev->enable) {
>> if (source_ops(csdev)->enable) {
>> - ret = coresight_control_assoc_ectdev(csdev, true);
>> - if (ret)
>> - return ret;
>> ret = source_ops(csdev)->enable(csdev, data, mode);
>> - if (ret) {
>> - coresight_control_assoc_ectdev(csdev, false);
>> + if (ret)
>> return ret;
>> - }
>> }
>> csdev->enable = true;
>> }
>> @@ -499,7 +461,6 @@ bool coresight_disable_source(struct
>> coresight_device *csdev, void *data)
>> if (atomic_dec_return(&csdev->refcnt) == 0) {
>> if (source_ops(csdev)->disable)
>> source_ops(csdev)->disable(csdev, data);
>> - coresight_control_assoc_ectdev(csdev, false);
>> coresight_disable_helpers(csdev);
>> csdev->enable = false;
>> }
>> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c
>> b/drivers/hwtracing/coresight/coresight-cti-core.c
>> index 277c890a1f1f..db7a2212ec18 100644
>> --- a/drivers/hwtracing/coresight/coresight-cti-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
>> @@ -555,7 +555,10 @@ static void cti_add_assoc_to_csdev(struct
>> coresight_device *csdev)
>> mutex_lock(&ect_mutex);
>> /* exit if current is an ECT device.*/
>> - if ((csdev->type == CORESIGHT_DEV_TYPE_ECT) || list_empty(&ect_net))
>> + if ((csdev->type == CORESIGHT_DEV_TYPE_HELPER &&
>> + csdev->subtype.helper_subtype ==
>> + CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI) ||
>> + list_empty(&ect_net))
>> goto cti_add_done;
>> /* if we didn't find the csdev previously we used the fwnode
>> name */
>> @@ -571,8 +574,7 @@ static void cti_add_assoc_to_csdev(struct
>> coresight_device *csdev)
>> * if we found a matching csdev then update the ECT
>> * association pointer for the device with this CTI.
>> */
>> - coresight_set_assoc_ectdev_mutex(csdev,
>> - ect_item->csdev);
>> + coresight_add_helper_mutex(csdev, ect_item->csdev);
>> break;
>> }
>> }
>> @@ -582,26 +584,30 @@ static void cti_add_assoc_to_csdev(struct
>> coresight_device *csdev)
>> /*
>> * Removing the associated devices is easier.
>> - * A CTI will not have a value for csdev->ect_dev.
>> */
>> static void cti_remove_assoc_from_csdev(struct coresight_device *csdev)
>> {
>> struct cti_drvdata *ctidrv;
>> struct cti_trig_con *tc;
>> + union coresight_dev_subtype cti_subtype = {
>> + .helper_subtype = CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI
>> + };
>> + struct coresight_device *cti_csdev = coresight_find_output_type(
>> + csdev->pdata, CORESIGHT_DEV_TYPE_HELPER, cti_subtype);
>
> minor nit: Please could we split the initialisation ? Or at least move
> this after the next variable declaration below ?
>
>
> Rest looks fine to me.
>
> Suzuki
>
>> struct cti_device *ctidev;
>> + if (!cti_csdev)
>> + return;
>> +
>> mutex_lock(&ect_mutex);
>> - if (csdev->ect_dev) {
>> - ctidrv = csdev_to_cti_drvdata(csdev->ect_dev);
>> - ctidev = &ctidrv->ctidev;
>> - list_for_each_entry(tc, &ctidev->trig_cons, node) {
>> - if (tc->con_dev == csdev) {
>> - cti_remove_sysfs_link(ctidrv, tc);
>> - tc->con_dev = NULL;
>> - break;
>> - }
>> + ctidrv = csdev_to_cti_drvdata(cti_csdev);
>> + ctidev = &ctidrv->ctidev;
>> + list_for_each_entry(tc, &ctidev->trig_cons, node) {
>> + if (tc->con_dev == csdev) {
>> + cti_remove_sysfs_link(ctidrv, tc);
>> + tc->con_dev = NULL;
>> + break;
>> }
>> - csdev->ect_dev = NULL;
>> }
>> mutex_unlock(&ect_mutex);
>> }
>> @@ -630,8 +636,8 @@ static void cti_update_conn_xrefs(struct
>> cti_drvdata *drvdata)
>> /* if we can set the sysfs link */
>> if (cti_add_sysfs_link(drvdata, tc))
>> /* set the CTI/csdev association */
>> - coresight_set_assoc_ectdev_mutex(tc->con_dev,
>> - drvdata->csdev);
>> + coresight_add_helper_mutex(tc->con_dev,
>> + drvdata->csdev);
>> else
>> /* otherwise remove reference from CTI */
>> tc->con_dev = NULL;
>> @@ -646,8 +652,6 @@ static void cti_remove_conn_xrefs(struct
>> cti_drvdata *drvdata)
>> list_for_each_entry(tc, &ctidev->trig_cons, node) {
>> if (tc->con_dev) {
>> - coresight_set_assoc_ectdev_mutex(tc->con_dev,
>> - NULL);
>> cti_remove_sysfs_link(drvdata, tc);
>> tc->con_dev = NULL;
>> }
>> @@ -795,27 +799,27 @@ static void cti_pm_release(struct cti_drvdata
>> *drvdata)
>> }
>> /** cti ect operations **/
>> -int cti_enable(struct coresight_device *csdev)
>> +int cti_enable(struct coresight_device *csdev, enum cs_mode mode,
>> void *data)
>> {
>> struct cti_drvdata *drvdata = csdev_to_cti_drvdata(csdev);
>> return cti_enable_hw(drvdata);
>> }
>> -int cti_disable(struct coresight_device *csdev)
>> +int cti_disable(struct coresight_device *csdev, void *data)
>> {
>> struct cti_drvdata *drvdata = csdev_to_cti_drvdata(csdev);
>> return cti_disable_hw(drvdata);
>> }
>> -static const struct coresight_ops_ect cti_ops_ect = {
>> +static const struct coresight_ops_helper cti_ops_ect = {
>> .enable = cti_enable,
>> .disable = cti_disable,
>> };
>> static const struct coresight_ops cti_ops = {
>> - .ect_ops = &cti_ops_ect,
>> + .helper_ops = &cti_ops_ect,
>> };
>> /*
>> @@ -922,8 +926,8 @@ static int cti_probe(struct amba_device *adev,
>> const struct amba_id *id)
>> /* set up coresight component description */
>> cti_desc.pdata = pdata;
>> - cti_desc.type = CORESIGHT_DEV_TYPE_ECT;
>> - cti_desc.subtype.ect_subtype = CORESIGHT_DEV_SUBTYPE_ECT_CTI;
>> + cti_desc.type = CORESIGHT_DEV_TYPE_HELPER;
>> + cti_desc.subtype.helper_subtype =
>> CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI;
>> cti_desc.ops = &cti_ops;
>> cti_desc.groups = drvdata->ctidev.con_groups;
>> cti_desc.dev = dev;
>> diff --git a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>> b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>> index e528cff9d4e2..d25dd2737b49 100644
>> --- a/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>> +++ b/drivers/hwtracing/coresight/coresight-cti-sysfs.c
>> @@ -112,11 +112,11 @@ static ssize_t enable_store(struct device *dev,
>> ret = pm_runtime_resume_and_get(dev->parent);
>> if (ret)
>> return ret;
>> - ret = cti_enable(drvdata->csdev);
>> + ret = cti_enable(drvdata->csdev, CS_MODE_SYSFS, NULL);
>> if (ret)
>> pm_runtime_put(dev->parent);
>> } else {
>> - ret = cti_disable(drvdata->csdev);
>> + ret = cti_disable(drvdata->csdev, NULL);
>> if (!ret)
>> pm_runtime_put(dev->parent);
>> }
>> diff --git a/drivers/hwtracing/coresight/coresight-cti.h
>> b/drivers/hwtracing/coresight/coresight-cti.h
>> index 8b106b13a244..cb9ee616d01f 100644
>> --- a/drivers/hwtracing/coresight/coresight-cti.h
>> +++ b/drivers/hwtracing/coresight/coresight-cti.h
>> @@ -215,8 +215,8 @@ int cti_add_connection_entry(struct device *dev,
>> struct cti_drvdata *drvdata,
>> const char *assoc_dev_name);
>> struct cti_trig_con *cti_allocate_trig_con(struct device *dev, int
>> in_sigs,
>> int out_sigs);
>> -int cti_enable(struct coresight_device *csdev);
>> -int cti_disable(struct coresight_device *csdev);
>> +int cti_enable(struct coresight_device *csdev, enum cs_mode mode,
>> void *data);
>> +int cti_disable(struct coresight_device *csdev, void *data);
>> void cti_write_all_hw_regs(struct cti_drvdata *drvdata);
>> void cti_write_intack(struct device *dev, u32 ackval);
>> void cti_write_single_reg(struct cti_drvdata *drvdata, int offset,
>> u32 value);
>> diff --git a/drivers/hwtracing/coresight/coresight-priv.h
>> b/drivers/hwtracing/coresight/coresight-priv.h
>> index a843f9d5c737..fff565d1cb42 100644
>> --- a/drivers/hwtracing/coresight/coresight-priv.h
>> +++ b/drivers/hwtracing/coresight/coresight-priv.h
>> @@ -211,8 +211,8 @@ void coresight_release_platform_data(struct
>> coresight_device *csdev,
>> struct coresight_platform_data *pdata);
>> struct coresight_device *
>> coresight_find_csdev_by_fwnode(struct fwnode_handle *r_fwnode);
>> -void coresight_set_assoc_ectdev_mutex(struct coresight_device *csdev,
>> - struct coresight_device *ect_csdev);
>> +void coresight_add_helper_mutex(struct coresight_device *csdev,
>> + struct coresight_device *helper);
>> void coresight_set_percpu_sink(int cpu, struct coresight_device
>> *csdev);
>> struct coresight_device *coresight_get_percpu_sink(int cpu);
>> diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c
>> b/drivers/hwtracing/coresight/coresight-sysfs.c
>> index 464ba5e1343b..dd78e9fcfc4d 100644
>> --- a/drivers/hwtracing/coresight/coresight-sysfs.c
>> +++ b/drivers/hwtracing/coresight/coresight-sysfs.c
>> @@ -148,6 +148,10 @@ int coresight_make_links(struct coresight_device
>> *orig,
>> char *outs = NULL, *ins = NULL;
>> struct coresight_sysfs_link *link = NULL;
>> + /* Helper devices aren't shown in sysfs */
>> + if (conn->dest_port == -1 && conn->src_port == -1)
>> + return 0;
>> +
>> do {
>> outs = devm_kasprintf(&orig->dev, GFP_KERNEL,
>> "out:%d", conn->src_port);
>> diff --git a/include/linux/coresight.h b/include/linux/coresight.h
>> index d2739a0286f1..ed37552761e4 100644
>> --- a/include/linux/coresight.h
>> +++ b/include/linux/coresight.h
>> @@ -40,8 +40,7 @@ enum coresight_dev_type {
>> CORESIGHT_DEV_TYPE_LINK,
>> CORESIGHT_DEV_TYPE_LINKSINK,
>> CORESIGHT_DEV_TYPE_SOURCE,
>> - CORESIGHT_DEV_TYPE_HELPER,
>> - CORESIGHT_DEV_TYPE_ECT,
>> + CORESIGHT_DEV_TYPE_HELPER
>> };
>> enum coresight_dev_subtype_sink {
>> @@ -66,12 +65,7 @@ enum coresight_dev_subtype_source {
>> enum coresight_dev_subtype_helper {
>> CORESIGHT_DEV_SUBTYPE_HELPER_CATU,
>> -};
>> -
>> -/* Embedded Cross Trigger (ECT) sub-types */
>> -enum coresight_dev_subtype_ect {
>> - CORESIGHT_DEV_SUBTYPE_ECT_NONE,
>> - CORESIGHT_DEV_SUBTYPE_ECT_CTI,
>> + CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI
>> };
>> /**
>> @@ -84,8 +78,6 @@ enum coresight_dev_subtype_ect {
>> * by @coresight_dev_subtype_source.
>> * @helper_subtype: type of helper this component is, as defined
>> * by @coresight_dev_subtype_helper.
>> - * @ect_subtype: type of cross trigger this component is, as
>> - * defined by @coresight_dev_subtype_ect
>> */
>> union coresight_dev_subtype {
>> /* We have some devices which acts as LINK and SINK */
>> @@ -95,7 +87,6 @@ union coresight_dev_subtype {
>> };
>> enum coresight_dev_subtype_source source_subtype;
>> enum coresight_dev_subtype_helper helper_subtype;
>> - enum coresight_dev_subtype_ect ect_subtype;
>> };
>> /**
>> @@ -237,8 +228,6 @@ struct coresight_sysfs_link {
>> * from source to that sink.
>> * @ea: Device attribute for sink representation under PMU
>> directory.
>> * @def_sink: cached reference to default sink found for this
>> device.
>> - * @ect_dev: Associated cross trigger device. Not part of the
>> trace data
>> - * path or connections.
>> * @nr_links: number of sysfs links created to other components
>> from this
>> * device. These will appear in the "connections" group.
>> * @has_conns_grp: Have added a "connections" group for sysfs links.
>> @@ -261,12 +250,9 @@ struct coresight_device {
>> bool activated; /* true only if a sink is part of a path */
>> struct dev_ext_attribute *ea;
>> struct coresight_device *def_sink;
>> - /* cross trigger handling */
>> - struct coresight_device *ect_dev;
>> /* sysfs links between components */
>> int nr_links;
>> bool has_conns_grp;
>> - bool ect_enabled; /* true only if associated ect device is
>> enabled */
>> /* system configuration and feature lists */
>> struct list_head feature_csdev_list;
>> struct list_head config_csdev_list;
>> @@ -378,23 +364,11 @@ struct coresight_ops_helper {
>> int (*disable)(struct coresight_device *csdev, void *data);
>> };
>> -/**
>> - * struct coresight_ops_ect - Ops for an embedded cross trigger device
>> - *
>> - * @enable : Enable the device
>> - * @disable : Disable the device
>> - */
>> -struct coresight_ops_ect {
>> - int (*enable)(struct coresight_device *csdev);
>> - int (*disable)(struct coresight_device *csdev);
>> -};
>> -
>> struct coresight_ops {
>> const struct coresight_ops_sink *sink_ops;
>> const struct coresight_ops_link *link_ops;
>> const struct coresight_ops_source *source_ops;
>> const struct coresight_ops_helper *helper_ops;
>> - const struct coresight_ops_ect *ect_ops;
>> };
>> #if IS_ENABLED(CONFIG_CORESIGHT)
>
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