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Message-ID: <64bdcca3-b54f-37de-0bee-2f79c1511da1@quicinc.com>
Date: Wed, 9 Mar 2022 22:27:10 +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>, <quic_jinlmao@...cinc.com>
Subject: Re: [PATCH v2] coresight: core: Fix coresight device probe failure
issue
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@....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 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
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