[PATCH 3/3] drm/amdgpu: fix gpu reset issue

Christian König deathsimple at vodafone.de
Thu May 4 11:32:58 UTC 2017 

That's what we used to have with the exclusive lock.

The issue is not what kind of lock or locking or not locking at all, but 
rather where to place it.

Having a rw lock called something like "in_reset" is ok to me, but we 
shouldn't take it in the IOCTL path.

Instead we should block for example the GART TLB flush while being 
inside a reset etc...

Otherwise we run into the same problems (lock inversions for example) as 
we had before.

Regards,
Christian.

Am 04.05.2017 um 13:28 schrieb Liu, Monk:
> Christian
>
> Why not use rw lock ? that way only gpu reset will make those iOCTL blocked,
> and in usual case the performance is still the same
>
> BR Monk
>
> -----Original Message-----
> From: amd-gfx [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf Of Christian König
> Sent: Thursday, May 04, 2017 7:21 PM
> To: Zhou, David(ChunMing) <David1.Zhou at amd.com>; He, Hongbo <Hongbo.He at amd.com>; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH 3/3] drm/amdgpu: fix gpu reset issue
>
> But that should be harmless because we rebuild the GART table after GPU reset, don't we?
>
> Apart from that I'm fine with having a lock or locks to prevent concurrent things from happening while we do the reset.
>
> But we should NOT do the mistake again and try to prevent everything is one big global lock. That was rather bad idea and using an atomic isn't better in any way.
>
> Regards,
> Christian.
>
> Am 04.05.2017 um 12:31 schrieb zhoucm1:
>> Hi Christian,
>>
>> We possibly must re-consider this patch, the direct issue is VM FAULT
>> after gpu reset. one obvious bug is we could bind gtt to gart during
>> GPU reset, binding gtt to gart needs to fill gart table and tlb flush,
>> which is parallel with gpu reset thread.
>>
>> Regards,
>> David Zhou
>>
>> On 2017年04月21日 16:27, Christian König wrote:
>>> NAK, that is exactly what we wanted to avoid.
>>>
>>> We used to have an exclusive lock for this and it cause a whole bunch
>>> of problems.
>>>
>>> Please elaborate why that should be necessary.
>>>
>>> Regards,
>>> Christian.
>>>
>>> Am 21.04.2017 um 09:08 schrieb Roger.He:
>>>> Change-Id: Ib77d33a09f348ebf2e3a9d7861411f4b951ebf7c
>>>> Signed-off-by: Roger.He <Hongbo.He at amd.com>
>>>> ---
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  6 ++++++
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 16 +++++++++++++++-
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c    |  4 ++++
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_ioc32.c  |  7 ++++++-
>>>>    4 files changed, 31 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> index 71364f5..ab0ffa8 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>> @@ -1526,6 +1526,7 @@ struct amdgpu_device {
>>>>        atomic64_t            num_bytes_moved;
>>>>        atomic64_t            num_evictions;
>>>>        atomic_t            gpu_reset_counter;
>>>> +    atomic_t            gpu_reset_state;
>>>>          /* data for buffer migration throttling */
>>>>        struct {
>>>> @@ -1851,6 +1852,11 @@ amdgpu_get_sdma_instance(struct amdgpu_ring
>>>> *ring)
>>>>    #define amdgpu_psp_check_fw_loading_status(adev, i)
>>>> (adev)->firmware.funcs->check_fw_loading_status((adev), (i))
>>>>      /* Common functions */
>>>> +static inline int amdgpu_device_is_reset(struct amdgpu_device
>>>> +*adev) {
>>>> +    return atomic_read(&adev->gpu_reset_state);
>>>> +}
>>>> +
>>>>    int amdgpu_gpu_reset(struct amdgpu_device *adev);
>>>>    bool amdgpu_need_backup(struct amdgpu_device *adev);
>>>>    void amdgpu_pci_config_reset(struct amdgpu_device *adev); diff
>>>> --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> index f882496..0fb4716 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>> @@ -1894,6 +1894,7 @@ int amdgpu_device_init(struct amdgpu_device
>>>> *adev,
>>>>        mutex_init(&adev->grbm_idx_mutex);
>>>>        mutex_init(&adev->mn_lock);
>>>>        hash_init(adev->mn_hash);
>>>> +    atomic_set(&adev->gpu_reset_state, 0);
>>>>          amdgpu_check_arguments(adev);
>>>>    @@ -2655,6 +2656,18 @@ int amdgpu_sriov_gpu_reset(struct
>>>> amdgpu_device *adev, bool voluntary)
>>>>    }
>>>>      /**
>>>> + * amdgpu_device_set_reset_state - set gpu reset state
>>>> + *
>>>> + * @adev: amdgpu device pointer
>>>> + * @state: true when start to reset gpu; false: reset done  */
>>>> +static inline void amdgpu_device_set_reset_state(struct
>>>> amdgpu_device *adev,
>>>> +                            bool state) {
>>>> +    atomic_set(&adev->gpu_reset_state, state); }
>>>> +
>>>> +/**
>>>>     * amdgpu_gpu_reset - reset the asic
>>>>     *
>>>>     * @adev: amdgpu device pointer
>>>> @@ -2678,7 +2691,7 @@ int amdgpu_gpu_reset(struct amdgpu_device *adev)
>>>>        }
>>>>          atomic_inc(&adev->gpu_reset_counter);
>>>> -
>>>> +    amdgpu_device_set_reset_state(adev, true);
>>>>        /* block TTM */
>>>>        resched = ttm_bo_lock_delayed_workqueue(&adev->mman.bdev);
>>>>        /* store modesetting */
>>>> @@ -2811,6 +2824,7 @@ int amdgpu_gpu_reset(struct amdgpu_device *adev)
>>>>            dev_info(adev->dev, "GPU reset failed\n");
>>>>        }
>>>>    +    amdgpu_device_set_reset_state(adev, false);
>>>>        return r;
>>>>    }
>>>>    diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>> index ead00d7..8cc14af 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>> @@ -679,11 +679,15 @@ long amdgpu_drm_ioctl(struct file *filp,
>>>>        struct drm_file *file_priv = filp->private_data;
>>>>        struct drm_device *dev;
>>>>        long ret;
>>>> +
>>>>        dev = file_priv->minor->dev;
>>>>        ret = pm_runtime_get_sync(dev->dev);
>>>>        if (ret < 0)
>>>>            return ret;
>>>>    +    while (amdgpu_device_is_reset(dev->dev_private))
>>>> +        msleep(100);
>>>> +
>>>>        ret = drm_ioctl(filp, cmd, arg);
>>>>          pm_runtime_mark_last_busy(dev->dev);
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ioc32.c
>>>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ioc32.c
>>>> index 2648291..22b8059 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ioc32.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ioc32.c
>>>> @@ -36,10 +36,15 @@
>>>>    long amdgpu_kms_compat_ioctl(struct file *filp, unsigned int cmd,
>>>> unsigned long arg)
>>>>    {
>>>>        unsigned int nr = DRM_IOCTL_NR(cmd);
>>>> +    struct drm_file *file_priv = filp->private_data;
>>>> +    struct amdgpu_device *adev =
>>>> + file_priv->minor->dev->dev_private;
>>>>        int ret;
>>>>    -    if (nr < DRM_COMMAND_BASE)
>>>> +    if (nr < DRM_COMMAND_BASE) {
>>>> +        while (amdgpu_device_is_reset(adev))
>>>> +            msleep(100);
>>>>            return drm_compat_ioctl(filp, cmd, arg);
>>>> +    }
>>>>          ret = amdgpu_drm_ioctl(filp, cmd, arg);
>>>
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