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@xxxxxxx>
>
> -----Original Message-----
> From: amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of StDenis, Tom
> Sent: Monday, January 7, 2019 10:16 AM
> To: amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: StDenis, Tom <Tom.StDenis@xxxxxxx>
> 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@xxxxxxx>
> ---
> 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.
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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