[PATCH] add missing mutex lock to amdgpu_get_xgmi_hive() (v2)
Grodzovsky, Andrey
Andrey.Grodzovsky at amd.com
Mon Jan 7 16:51:58 UTC 2019
On 01/07/2019 11:36 AM, StDenis, Tom wrote:
> On 2019-01-07 11:33 a.m., Grodzovsky, Andrey wrote:
>>
>> On 01/07/2019 11:16 AM, Liu, Shaoyun wrote:
>>> I think it's reasonable to use the hive specific lock for hive specific functions.
>>> The changes is acked-by Shaoyun.liu < Shaoyun.liu at amd.com>
>>>
>>> -----Original Message-----
>>> From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> On Behalf Of StDenis, Tom
>>> Sent: Monday, January 7, 2019 10:16 AM
>>> To: amd-gfx at lists.freedesktop.org
>>> Cc: StDenis, Tom <Tom.StDenis at amd.com>
>>> Subject: [PATCH] add missing mutex lock to amdgpu_get_xgmi_hive() (v2)
>>>
>>> v2: Move locks around in other functions so that this function can stand on its own. Also only hold the hive specific lock for add/remove device instead of the driver global lock so you can't add/remove devices in parallel from one hive.
>>>
>>> Signed-off-by: Tom St Denis <tom.stdenis at amd.com>
>>> ---
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 2 +-
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c | 36 ++++++++++++++--------
>>> drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h | 2 +-
>>> 3 files changed, 25 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> index 39d5d058b2c7..13d8e2ad2f7a 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>> @@ -3525,7 +3525,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
>>> * by different nodes. No point also since the one node already executing
>>> * reset will also reset all the other nodes in the hive.
>>> */
>>> - hive = amdgpu_get_xgmi_hive(adev);
>>> + hive = amdgpu_get_xgmi_hive(adev, 0);
>>> if (hive && adev->gmc.xgmi.num_physical_nodes > 1 &&
>>> !mutex_trylock(&hive->hive_lock))
>>> return 0;
>> Let's say i have device 0 in hive A and it just got a gpu reset and at
>> the same time device 1 is being added to same have though
>> amdgpu_xgmi_add_device, hive->hive_lock is acquired by this new device
>> being added and so gpu reset for device 0 bails out on
>> '!mutex_trylock(&hive->hive_lock))' without completing the reset.
>> Also in general i feel a bit uncomfortable about the confusing
>> acquisition scheme in the function and the fact that you take the
>> hive->hive_lock inside amdgpu_get_xgmi_hive but release is still outside
>> of the function.
> Is adding a device while resetting a device even a valid operation
> anyways?
In theory it's valid if you have hot pluggable devices
>
> I think this means more so that the reset logic is broken. Instead
> there should be a per-hive reset lock that is taken and that is tested
> instead.
>
> Tom
The hive->hive_lock was added exactly for this purpose and used only for
that purpose. Maybe the naming i gave it wasn't reflective of it's
purpose :)
Andrey
>
>
>> Andrey
>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
>>> index 8a8bc60cb6b4..ebf50809485f 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.c
>>> @@ -40,26 +40,39 @@ void *amdgpu_xgmi_hive_try_lock(struct amdgpu_hive_info *hive)
>>> return &hive->device_list;
>>> }
>>>
>>> -struct amdgpu_hive_info *amdgpu_get_xgmi_hive(struct amdgpu_device *adev)
>>> +struct amdgpu_hive_info *amdgpu_get_xgmi_hive(struct amdgpu_device
>>> +*adev, int lock)
>>> {
>>> int i;
>>> struct amdgpu_hive_info *tmp;
>>>
>>> if (!adev->gmc.xgmi.hive_id)
>>> return NULL;
>>> +
>>> + mutex_lock(&xgmi_mutex);
>>> +
>>> for (i = 0 ; i < hive_count; ++i) {
>>> tmp = &xgmi_hives[i];
>>> - if (tmp->hive_id == adev->gmc.xgmi.hive_id)
>>> + if (tmp->hive_id == adev->gmc.xgmi.hive_id) {
>>> + if (lock)
>>> + mutex_lock(&tmp->hive_lock);
>>> + mutex_unlock(&xgmi_mutex);
>>> return tmp;
>>> + }
>>> }
>>> - if (i >= AMDGPU_MAX_XGMI_HIVE)
>>> + if (i >= AMDGPU_MAX_XGMI_HIVE) {
>>> + mutex_unlock(&xgmi_mutex);
>>> return NULL;
>>> + }
>>>
>>> /* initialize new hive if not exist */
>>> tmp = &xgmi_hives[hive_count++];
>>> tmp->hive_id = adev->gmc.xgmi.hive_id;
>>> INIT_LIST_HEAD(&tmp->device_list);
>>> mutex_init(&tmp->hive_lock);
>>> + if (lock)
>>> + mutex_lock(&tmp->hive_lock);
>>> +
>>> + mutex_unlock(&xgmi_mutex);
>>>
>>> return tmp;
>>> }
>>> @@ -111,8 +124,8 @@ int amdgpu_xgmi_add_device(struct amdgpu_device *adev)
>>> return ret;
>>> }
>>>
>>> - mutex_lock(&xgmi_mutex);
>>> - hive = amdgpu_get_xgmi_hive(adev);
>>> + /* find hive and take lock */
>>> + hive = amdgpu_get_xgmi_hive(adev, 1);
>>> if (!hive)
>>> goto exit;
>>>
>>> @@ -142,8 +155,8 @@ int amdgpu_xgmi_add_device(struct amdgpu_device *adev)
>>> break;
>>> }
>>>
>>> + mutex_unlock(&hive->hive_lock);
>>> exit:
>>> - mutex_unlock(&xgmi_mutex);
>>> return ret;
>>> }
>>>
>>> @@ -154,15 +167,12 @@ void amdgpu_xgmi_remove_device(struct amdgpu_device *adev)
>>> if (!adev->gmc.xgmi.supported)
>>> return;
>>>
>>> - mutex_lock(&xgmi_mutex);
>>> -
>>> - hive = amdgpu_get_xgmi_hive(adev);
>>> + hive = amdgpu_get_xgmi_hive(adev, 1);
>>> if (!hive)
>>> - goto exit;
>>> + return;
>>>
>>> if (!(hive->number_devices--))
>>> mutex_destroy(&hive->hive_lock);
>>> -
>>> -exit:
>>> - mutex_unlock(&xgmi_mutex);
>>> + else
>>> + mutex_unlock(&hive->hive_lock);
>>> }
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h
>>> index 6151eb9c8ad3..8d7984844174 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xgmi.h
>>> @@ -32,7 +32,7 @@ struct amdgpu_hive_info {
>>> struct mutex hive_lock;
>>> };
>>>
>>> -struct amdgpu_hive_info *amdgpu_get_xgmi_hive(struct amdgpu_device *adev);
>>> +struct amdgpu_hive_info *amdgpu_get_xgmi_hive(struct amdgpu_device
>>> +*adev, int lock);
>>> int amdgpu_xgmi_update_topology(struct amdgpu_hive_info *hive, struct amdgpu_device *adev); int amdgpu_xgmi_add_device(struct amdgpu_device *adev); void amdgpu_xgmi_remove_device(struct amdgpu_device *adev);
>>> --
>>> 2.17.2
>>>
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