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

[Jinlong Mao]

Hi Suzuki,

On 3/9/2022 10:57 AM, Jinlong Mao wrote:
> 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 tested with your changes.
No probe failure during reboot stress test.
I submit "[PATCH v3] coresight: core: Fix coresight device probe failure 
issue".
Please help to review.

Thanks
Jinlong Mao

> I will test with your changes and get back to you later.
>
> Thanks
> Jinlong Mao
>>
>> Thanks
>> Suzuki