[PATCH v5 13/13] coresight: Fix CTI module refcount leak by making it a helper device
Suzuki K Poulose
suzuki.poulose at arm.com
Mon Apr 24 03:43:11 PDT 2023
On 04/04/2023 16:51, 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 at arm.com>
> ---
> drivers/hwtracing/coresight/coresight-core.c | 104 ++++++------------
> .../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, 75 insertions(+), 127 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
> index 16689fe4ba98..2af416bba983 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -236,60 +236,44 @@ 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)
> +/*
> + * Add a helper as an output device. This function takes the @coresight_mutex
> + * because it's assumed that it's called from the helper device, outside of the
> + * core code where the mutex would already be held. Don't add new calls to this
> + * from inside the core code, instead try to add the new helper to the DT and
> + * ACPI where it will be picked up and linked automatically.
> + */
> +void coresight_add_helper(struct coresight_device *csdev,
> + struct coresight_device *helper)
> {
> - int ect_ret = 0;
> - struct coresight_device *ect_csdev = csdev->ect_dev;
> - struct module *mod;
> + int i;
> + struct coresight_connection conn = {};
> + struct coresight_connection *new_conn;
>
> - if (!ect_csdev)
> - return 0;
> - if ((!ect_ops(ect_csdev)->enable) || (!ect_ops(ect_csdev)->disable))
> - return 0;
> + mutex_lock(&coresight_mutex);
> + 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;
>
> - 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;
> - }
> - }
> + /*
> + * Check for duplicates because this is called every time a helper
> + * device is re-loaded. Existing connections will get re-linked
> + * automatically.
> + */
> + for (i = 0; i < csdev->pdata->nr_outconns; ++i)
> + if (csdev->pdata->out_conns[i]->dest_fwnode == conn.dest_fwnode)
> + goto unlock;
>
> - /* 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;
> -}
> + new_conn =
> + coresight_add_out_conn(csdev->dev.parent, csdev->pdata, &conn);
ultra minor nit:
new_conn = coresight_add_out_conn(....,
.... );
> + if (!IS_ERR(new_conn))
> + coresight_add_in_conn(new_conn);
>
> -/*
> - * 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.
> - */
> -void coresight_set_assoc_ectdev_mutex(struct coresight_device *csdev,
> - struct coresight_device *ect_csdev)
> -{
> - mutex_lock(&coresight_mutex);
> - csdev->ect_dev = ect_csdev;
> +unlock:
> mutex_unlock(&coresight_mutex);
> }
> -EXPORT_SYMBOL_GPL(coresight_set_assoc_ectdev_mutex);
> +EXPORT_SYMBOL_GPL(coresight_add_helper);
>
> static int coresight_enable_sink(struct coresight_device *csdev,
> enum cs_mode mode, void *data)
> @@ -303,12 +287,8 @@ 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;
> @@ -326,7 +306,6 @@ 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;
> }
>
> @@ -351,17 +330,11 @@ 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;
> }
>
> @@ -382,7 +355,6 @@ 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) {
> @@ -410,14 +382,9 @@ int coresight_enable_source(struct coresight_device *csdev, enum cs_mode mode,
>
> 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;
> }
> @@ -488,7 +455,6 @@ 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;
> }
You may also remove the "ect" from the
static struct device_type coresight_dev_type[]
Suzuki
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