[PATCH v2] coresight: core: Fix coresight device probe failure issue

[Jinlong Mao]

Hi Suzuki,

On 3/8/2022 9:36 PM, Suzuki K Poulose wrote:
> 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 at arm.com>
>>> Suggested-by: Mike Leach <mike.leach at linaro.org>
>>> Signed-off-by: Mao Jinlong <quic_jinlmao at quicinc.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);
>     }
I will test with your changes and get back to you later.

Thanks
Jinlong Mao
>
> Thanks
> Suzuki