Re: [PATCH v3 13/13] coresight: Fix CTI module refcount leak by making it a helper device

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@arm.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 :

might_sleep() and lockdep_assert_not_held(&coresight_mutex);

in the function.

{

• 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);

• 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)