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Message-ID: <7db54684-2637-ba82-7146-c8a559337933@quicinc.com>
Date: Wed, 9 Mar 2022 10:57:08 +0800
From: Jinlong Mao <quic_jinlmao@...cinc.com>
To: Suzuki K Poulose <suzuki.poulose@....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
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@....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);
> }
I will test with your changes and get back to you later.
Thanks
Jinlong Mao
>
> Thanks
> Suzuki
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