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Date: Tue, 8 Mar 2022 13:36:30 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Mao Jinlong <quic_jinlmao@...cinc.com>,
Mathieu Poirier <mathieu.poirier@...aro.org>,
Mike Leach <mike.leach@...aro.org>,
Leo Yan <leo.yan@...aro.org>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
Tingwei Zhang <quic_tingweiz@...cinc.com>,
Yuanfang Zhang <quic_yuanfang@...cinc.com>,
Tao Zhang <quic_taozha@...cinc.com>,
Hao Zhang <quic_hazha@...cinc.com>
Subject: Re: [PATCH v2] coresight: core: Fix coresight device probe failure
issue
On 08/03/2022 11:56, Suzuki K Poulose wrote:
> Hi Jinlong
>
> On 04/03/2022 08:23, Mao Jinlong wrote:
>> It is possibe that probe failure issue happens when the device
>> and its child_device's probe happens at the same time.
>> In coresight_make_links, has_conns_grp is true for parent, but
>> has_conns_grp is false for child device as has_conns_grp is set
>> to true in coresight_create_conns_sysfs_group. The probe of parent
>> device will fail at this condition. Add has_conns_grp check for
>> child device before make the links and make the process from
>> device_register to connection_create be atomic to avoid this
>> probe failure issue.
>>
>> Suggested-by: Suzuki K Poulose <suzuki.poulose@....com>
>> Suggested-by: Mike Leach <mike.leach@...aro.org>
>> Signed-off-by: Mao Jinlong <quic_jinlmao@...cinc.com>
>> ---
>> drivers/hwtracing/coresight/coresight-core.c | 12 ++++++------
>> 1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-core.c
>> b/drivers/hwtracing/coresight/coresight-core.c
>> index 88653d1c06a4..b3e3bc59c09b 100644
>> --- a/drivers/hwtracing/coresight/coresight-core.c
>> +++ b/drivers/hwtracing/coresight/coresight-core.c
>> @@ -1382,7 +1382,7 @@ static int coresight_fixup_device_conns(struct
>> coresight_device *csdev)
>> continue;
>> conn->child_dev =
>> coresight_find_csdev_by_fwnode(conn->child_fwnode);
>> - if (conn->child_dev) {
>> + if (conn->child_dev && conn->child_dev->has_conns_grp) {
>> ret = coresight_make_links(csdev, conn,
>> conn->child_dev);
>> if (ret)
>> @@ -1594,7 +1594,8 @@ struct coresight_device
>> *coresight_register(struct coresight_desc *desc)
>> refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
>> if (!refcnts) {
>> ret = -ENOMEM;
>> - goto err_free_csdev;
>> + kfree(csdev);
>> + goto err_out;
>> }
>> csdev->refcnt = refcnts;
>> @@ -1619,8 +1620,10 @@ struct coresight_device
>> *coresight_register(struct coresight_desc *desc)
>> csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
>> dev_set_name(&csdev->dev, "%s", desc->name);
>> + mutex_lock(&coresight_mutex);
>> ret = device_register(&csdev->dev);
>> if (ret) {
>> + mutex_unlock(&coresight_mutex);
>> put_device(&csdev->dev);
>> /*
>> * All resources are free'd explicitly via
>> @@ -1634,6 +1637,7 @@ struct coresight_device
>> *coresight_register(struct coresight_desc *desc)
>> ret = etm_perf_add_symlink_sink(csdev);
>> if (ret) {
>> + mutex_unlock(&coresight_mutex);
>> device_unregister(&csdev->dev);
>> /*
>> * As with the above, all resources are free'd
>> @@ -1645,8 +1649,6 @@ struct coresight_device
>> *coresight_register(struct coresight_desc *desc)
>> }
>> }
>> - mutex_lock(&coresight_mutex);
>> -
>> ret = coresight_create_conns_sysfs_group(csdev);
>> if (!ret)
>> ret = coresight_fixup_device_conns(csdev);
>> @@ -1663,8 +1665,6 @@ struct coresight_device
>> *coresight_register(struct coresight_desc *desc)
>> return csdev;
>> -err_free_csdev:
>> - kfree(csdev);
>> err_out:
>> /* Cleanup the connection information */
>> coresight_release_platform_data(NULL, desc->pdata);
>
> Could we consolidate the unlock sequence to a single point with
> something like this (untested):
>
>
> diff --git a/drivers/hwtracing/coresight/coresight-core.c
> b/drivers/hwtracing/coresight/coresight-core.c
> index af00dca8d1ac..198ee140c6e6 100644
> --- a/drivers/hwtracing/coresight/coresight-core.c
> +++ b/drivers/hwtracing/coresight/coresight-core.c
> @@ -1571,6 +1571,7 @@ struct coresight_device *coresight_register(struct
> coresight_desc *desc)
> int nr_refcnts = 1;
> atomic_t *refcnts = NULL;
> struct coresight_device *csdev;
> + bool registered = false;
>
> csdev = kzalloc(sizeof(*csdev), GFP_KERNEL);
> if (!csdev) {
> @@ -1591,7 +1592,8 @@ struct coresight_device *coresight_register(struct
> coresight_desc *desc)
> refcnts = kcalloc(nr_refcnts, sizeof(*refcnts), GFP_KERNEL);
> if (!refcnts) {
> ret = -ENOMEM;
> - goto err_free_csdev;
> + kfree(csdev);
> + goto err_out;
> }
>
> csdev->refcnt = refcnts;
> @@ -1616,6 +1618,13 @@ struct coresight_device
> *coresight_register(struct coresight_desc *desc)
> csdev->dev.fwnode = fwnode_handle_get(dev_fwnode(desc->dev));
> dev_set_name(&csdev->dev, "%s", desc->name);
>
> + /*
> + * Make sure the device registration and the connection fixup
> + * are synchronised, so that we don't see uninitialised devices
> + * on the coresight bus while trying to resolve the connections.
> + */
> + mutex_lock(&coresight_mutex);
> +
> ret = device_register(&csdev->dev);
> if (ret) {
> put_device(&csdev->dev);
> @@ -1623,7 +1632,7 @@ struct coresight_device *coresight_register(struct
> coresight_desc *desc)
> * All resources are free'd explicitly via
> * coresight_device_release(), triggered from put_device().
> */
> - goto err_out;
> + goto out_unlock;
> }
>
> if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
> @@ -1638,11 +1647,11 @@ struct coresight_device
> *coresight_register(struct coresight_desc *desc)
> * from put_device(), which is in turn called from
> * function device_unregister().
> */
> - goto err_out;
> + goto out_unlock;
> }
> }
> -
> - mutex_lock(&coresight_mutex);
> + /* Device is now registered */
> + registered = true;
>
> ret = coresight_create_conns_sysfs_group(csdev);
> if (!ret)
> @@ -1652,16 +1661,15 @@ struct coresight_device
> *coresight_register(struct coresight_desc *desc)
> if (!ret && cti_assoc_ops && cti_assoc_ops->add)
> cti_assoc_ops->add(csdev);
>
> +out_unlock:
> mutex_unlock(&coresight_mutex);
> - if (ret) {
> + /* Success */
> + if (!ret)
> + return csdev;
> +
> + /* Unregister the device if needed */
> + if (registered)
> coresight_unregister(csdev);
> - return ERR_PTR(ret);
> - }
Apologies, this should be preserved :
i.e,
if (registered) {
coresight_unregister(csdev);
return ERR_PTR(ret);
}
Thanks
Suzuki
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