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References: <20230310160610.742382-1-james.clark@arm.com> <20230310160610.742382-10-james.clark@arm.com>
In-Reply-To: <20230310160610.742382-10-james.clark@arm.com>
From:   Mike Leach <mike.leach@linaro.org>
Date:   Wed, 22 Mar 2023 09:29:21 +0000
Message-ID: <CAJ9a7VgBp9HjZBHobe99QK5B3vbp8y639Ap-FLqWhGm2AuTOLg@mail.gmail.com>
Subject: Re: [PATCH v2 9/9] coresight: Fix CTI module refcount leak by making
 it a helper device
To:     James Clark <james.clark@arm.com>
Cc:     coresight@lists.linaro.org,
        Mathieu Poirier <mathieu.poirier@linaro.org>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Leo Yan <leo.yan@linaro.org>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi James

On Fri, 10 Mar 2023 at 16:07, James Clark <james.clark@arm.com> 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  | 73 +++----------------
>  .../hwtracing/coresight/coresight-cti-core.c  | 56 +++++++++-----
>  .../hwtracing/coresight/coresight-cti-sysfs.c |  4 +-
>  drivers/hwtracing/coresight/coresight-cti.h   |  4 +-
>  include/linux/coresight.h                     | 28 +------
>  5 files changed, 53 insertions(+), 112 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 3e6ccd9e8d4e..94d84404fb29 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -253,48 +253,6 @@ 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
>   * to avoid a race with coresight_enable that may try to use this value.
> @@ -302,8 +260,14 @@ coresight_control_assoc_ectdev(struct coresight_device *csdev, bool enable)
>  void coresight_set_assoc_ectdev_mutex(struct coresight_device *csdev,
>                                       struct coresight_device *ect_csdev)

Now we have generic helpers this could become a generic "add helper"
routine - for helpers such as CTI that aren't picked up by the trace
data port graph that catches other things.

e.g.
coresight_set_assoc_helper_mutex(struct coresight_device *csdev,
struct coresight_device *helper_csdev)


Regards

Mike

>  {
> +       struct coresight_connection conn = {};
> +
>         mutex_lock(&coresight_mutex);
> -       csdev->ect_dev = ect_csdev;
> +       conn.remote_fwnode = fwnode_handle_get(dev_fwnode(&ect_csdev->dev));
> +       conn.remote_dev = ect_csdev;
> +       conn.remote_port = conn.port = -1;
> +       coresight_add_conn(csdev->dev.parent, csdev->pdata, &conn);
> +       coresight_fixup_inputs(csdev);
>         mutex_unlock(&coresight_mutex);
>  }
>  EXPORT_SYMBOL_GPL(coresight_set_assoc_ectdev_mutex);
> @@ -320,12 +284,8 @@ 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;
> @@ -343,7 +303,6 @@ 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;
>  }
>
> @@ -368,17 +327,11 @@ static int coresight_enable_link(struct coresight_device *csdev,
>                 return outport;
>
>         if (link_ops(csdev)->enable) {
> -               ret = coresight_control_assoc_ectdev(csdev, true);
> -               if (!ret) {
> -                       ret = link_ops(csdev)->enable(csdev, inport, outport);
> -                       if (ret)
> -                               coresight_control_assoc_ectdev(csdev, false);
> -               }
> +               ret = link_ops(csdev)->enable(csdev, inport, outport);
> +               if (!ret)
> +                       csdev->enable = true;
>         }
>
> -       if (!ret)
> -               csdev->enable = true;
> -
>         return ret;
>  }
>
> @@ -407,7 +360,6 @@ static void coresight_disable_link(struct coresight_device *csdev,
>
>         if (link_ops(csdev)->disable) {
>                 link_ops(csdev)->disable(csdev, inport, outport);
> -               coresight_control_assoc_ectdev(csdev, false);
>         }
>
>         for (i = 0; i < nr_conns; i++)
> @@ -424,12 +376,8 @@ static int coresight_enable_source(struct coresight_device *csdev,
>
>         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, NULL, mode);
>                         if (ret) {
> -                               coresight_control_assoc_ectdev(csdev, false);
>                                 return ret;
>                         }
>                 }
> @@ -482,7 +430,6 @@ static bool coresight_disable_source(struct coresight_device *csdev)
>         if (atomic_dec_return(csdev->refcnt) == 0) {
>                 if (source_ops(csdev)->disable)
>                         source_ops(csdev)->disable(csdev, NULL);
> -               coresight_control_assoc_ectdev(csdev, false);
>                 csdev->enable = false;
>         }
>         return !csdev->enable;
> diff --git a/drivers/hwtracing/coresight/coresight-cti-core.c b/drivers/hwtracing/coresight/coresight-cti-core.c
> index 277c890a1f1f..dbce6680759f 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 */
> @@ -580,6 +583,22 @@ static void cti_add_assoc_to_csdev(struct coresight_device *csdev)
>         mutex_unlock(&ect_mutex);
>  }
>
> +static struct coresight_device *cti__get_cti_device(struct coresight_device *csdev)
> +{
> +       int i;
> +       struct coresight_device *tmp;
> +
> +       for (i = 0; i < csdev->pdata->nr_outconns; i++) {
> +               tmp = csdev->pdata->out_conns[i].remote_dev;
> +
> +               if (tmp && tmp->type == CORESIGHT_DEV_TYPE_HELPER &&
> +                   tmp->subtype.helper_subtype ==
> +                           CORESIGHT_DEV_SUBTYPE_HELPER_ECT_CTI)
> +                       return tmp;
> +       }
> +       return NULL;
> +}
> +
>  /*
>   * Removing the associated devices is easier.
>   * A CTI will not have a value for csdev->ect_dev.
> @@ -588,20 +607,21 @@ static void cti_remove_assoc_from_csdev(struct coresight_device *csdev)
>  {
>         struct cti_drvdata *ctidrv;
>         struct cti_trig_con *tc;
> +       struct coresight_device *cti_csdev = cti__get_cti_device(csdev);
>         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);
>  }
> @@ -646,8 +666,6 @@ 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 +813,27 @@ 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 +940,8 @@ 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/include/linux/coresight.h b/include/linux/coresight.h
> index c6ee1634d813..cf7a8658ee88 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;
>  };
>
>  /**
> @@ -264,12 +255,9 @@ 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;
> @@ -377,23 +365,11 @@ 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)
> --
> 2.34.1
>


-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK