Re: [PATCH] drm/amdgpu: Add autodump debugfs node for gpu reset

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Hi Jiange,

FYI I'm working on adding a new "--autodump" command to umr that uses this feature.
This is not yet merged but you can find the code here: https://gitlab.freedesktop.org/pepp/umr/-/tree/autodump

> (3) At the same time, considering the use case of this node, I believe that only the first GPU reset is worthy of a dump.

If it's possible I'd like to be able to do multiple dumps instead of limiting ourselves to only the first one.

Thanks!
Pierre-Eric



> (4) I didn't implement race condition guard because I believe that this node caters for a cautious super-user and a single client is enough to do all the work. I can add the logic if you think it is necessary.
> 
> Jiange
> 
> -----Original Message-----
> From: Koenig, Christian <Christian.Koenig@xxxxxxx> 
> Sent: Thursday, April 23, 2020 4:53 PM
> To: Zhao, Jiange <Jiange.Zhao@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx
> Cc: Kuehling, Felix <Felix.Kuehling@xxxxxxx>; Pelloux-prayer, Pierre-eric <Pierre-eric.Pelloux-prayer@xxxxxxx>; Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Zhang, Hawking <Hawking.Zhang@xxxxxxx>; Liu, Monk <Monk.Liu@xxxxxxx>; Zhao, Jiange <Jiange.Zhao@xxxxxxx>
> Subject: Re: [PATCH] drm/amdgpu: Add autodump debugfs node for gpu reset
> 
> Am 23.04.20 um 09:19 schrieb jianzh@xxxxxxx:
>> From: Jiange Zhao <Jiange.Zhao@xxxxxxx>
>>
>> When GPU got timeout, it would notify an interested part of an 
>> opportunity to dump info before actual GPU reset.
>>
>> A usermode app would open 'autodump' node under debugfs system and 
>> poll() for readable/writable. When a GPU reset is due, amdgpu would 
>> notify usermode app through wait_queue_head and give it 10 minutes to 
>> dump info.
>>
>> After usermode app has done its work, this 'autodump' node is closed.
>> On node closure, amdgpu gets to know the dump is done through the 
>> completion that is triggered in release().
>>
>> There is no write or read callback because necessary info can be 
>> obtained through dmesg and umr. Messages back and forth between 
>> usermode app and amdgpu are unnecessary.
>>
>> Signed-off-by: Jiange Zhao <Jiange.Zhao@xxxxxxx>
>> ---
>>   drivers/gpu/drm/amd/amdgpu/amdgpu.h         |  9 +++
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c | 85 +++++++++++++++++++++
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h |  1 +
>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c  |  2 +
>>   4 files changed, 97 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> index bc1e0fd71a09..a505b547f242 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>> @@ -724,6 +724,13 @@ struct amd_powerplay {
>>   	const struct amd_pm_funcs *pp_funcs;
>>   };
>>   
>> +struct amdgpu_autodump {
>> +	bool				registered;
>> +	struct completion		completed;
> 
> Registered and completed seems to have the same meaning.
> 
>> +	struct dentry			*dentry;
>> +	struct wait_queue_head		gpu_hang_wait;
>> +};
>> +
>>   #define AMDGPU_RESET_MAGIC_NUM 64
>>   #define AMDGPU_MAX_DF_PERFMONS 4
>>   struct amdgpu_device {
>> @@ -990,6 +997,8 @@ struct amdgpu_device {
>>   	char				product_number[16];
>>   	char				product_name[32];
>>   	char				serial[16];
>> +
>> +	struct amdgpu_autodump		autodump;
>>   };
>>   
>>   static inline struct amdgpu_device *amdgpu_ttm_adev(struct 
>> ttm_bo_device *bdev) diff --git 
>> a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>> index 1a4894fa3693..cdd4bf00adee 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.c
>> @@ -74,8 +74,91 @@ int amdgpu_debugfs_add_files(struct amdgpu_device *adev,
>>   	return 0;
>>   }
>>   
>> +int amdgpu_debugfs_wait_dump(struct amdgpu_device *adev) { #if 
>> +defined(CONFIG_DEBUG_FS)
>> +	int ret;
>> +	unsigned long tmo = 600*HZ;
> 
> In general please declare constant lines first and variable like "i" or "r" last.
> 
>> +
>> +	if (!adev->autodump.registered)
>> +		return 0;
>> +
>> +	wake_up_interruptible(&adev->autodump.gpu_hang_wait);
>> +
>> +	ret = 
>> +wait_for_completion_interruptible_timeout(&adev->autodump.completed, 
>> +tmo);
> 
> This is racy, in other words it can happen that a new client opens up the debugfs file without being signaled but blocks the reset here.
> 
> You could use two completion structures to avoid that.
> 
>> +	if (ret == 0) { /* time out and dump tool still not finish its dump*/
>> +		pr_err("autodump: timeout before dump finished, move on to gpu recovery\n");
>> +		return -ETIMEDOUT;
>> +	}
>> +#endif
>> +	return 0;
>> +}
>> +
>>   #if defined(CONFIG_DEBUG_FS)
>>   
>> +static int amdgpu_debugfs_autodump_open(struct inode *inode, struct 
>> +file *file) {
>> +	int ret;
>> +	struct amdgpu_device *adev;
>> +
>> +	ret = simple_open(inode, file);
>> +	if (ret)
>> +		return ret;
>> +
>> +	adev = file->private_data;
>> +	if (adev->autodump.registered == true)
>> +		return -EINVAL;
> 
> Probably better to return -EBUSY here. And this is racy, and might need a lock e.g. multiple clients could open the file at the same time.
> 
> If we use a struct completion for registered we could use the spinlock of that one for protection here.
> 
>> +
>> +	adev->autodump.registered = true;
> 
> You also need to reset the completion structure here otherwise only the first GPU reset would work with this.
> 
>> +
>> +	return 0;
>> +}
>> +
>> +static int amdgpu_debugfs_autodump_release(struct inode *inode, 
>> +struct file *file) {
>> +	struct amdgpu_device *adev = file->private_data;
>> +
>> +	complete(&adev->autodump.completed);
>> +	adev->autodump.registered = false;
>> +
>> +	return 0;
>> +}
>> +
>> +unsigned int amdgpu_debugfs_autodump_poll(struct file *file, struct 
>> +poll_table_struct *poll_table) {
>> +	struct amdgpu_device *adev = file->private_data;
>> +
>> +	poll_wait(file, &adev->autodump.gpu_hang_wait, poll_table);
>> +
>> +	if (adev->in_gpu_reset)
>> +		return POLLIN | POLLRDNORM | POLLWRNORM;
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct file_operations autodump_debug_fops = {
>> +	.owner = THIS_MODULE,
>> +	.open = amdgpu_debugfs_autodump_open,
>> +	.poll = amdgpu_debugfs_autodump_poll,
>> +	.release = amdgpu_debugfs_autodump_release, };
>> +
>> +static int amdgpu_debugfs_autodump_init(struct amdgpu_device *adev) {
>> +	struct dentry *entry;
>> +
>> +	init_completion(&adev->autodump.completed);
>> +	init_waitqueue_head(&adev->autodump.gpu_hang_wait);
>> +	adev->autodump.registered = false;
>> +
>> +	entry = debugfs_create_file("autodump", 0600,
>> +			adev->ddev->primary->debugfs_root,
>> +			adev, &autodump_debug_fops);
>> +	adev->autodump.dentry = entry;
>> +
>> +	return 0;
>> +}
>> +
>>   /**
>>    * amdgpu_debugfs_process_reg_op - Handle MMIO register reads/writes
>>    *
>> @@ -1434,6 +1517,8 @@ int amdgpu_debugfs_init(struct amdgpu_device 
>> *adev)
>>   
>>   	amdgpu_ras_debugfs_create_all(adev);
>>   
>> +	amdgpu_debugfs_autodump_init(adev);
>> +
>>   	return amdgpu_debugfs_add_files(adev, amdgpu_debugfs_list,
>>   					ARRAY_SIZE(amdgpu_debugfs_list));
>>   }
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h 
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h
>> index de12d1101526..9428940a696d 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_debugfs.h
>> @@ -40,3 +40,4 @@ int amdgpu_debugfs_add_files(struct amdgpu_device *adev,
>>   int amdgpu_debugfs_fence_init(struct amdgpu_device *adev);
>>   int amdgpu_debugfs_firmware_init(struct amdgpu_device *adev);
>>   int amdgpu_debugfs_gem_init(struct amdgpu_device *adev);
>> +int amdgpu_debugfs_wait_dump(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 3d601d5dd5af..44e54ea7af0f 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>> @@ -3915,6 +3915,8 @@ static int amdgpu_device_pre_asic_reset(struct amdgpu_device *adev,
>>   	int i, r = 0;
>>   	bool need_full_reset  = *need_full_reset_arg;
>>   
>> +	amdgpu_debugfs_wait_dump(adev);
>> +
>>   	/* block all schedulers and reset given job's ring */
>>   	for (i = 0; i < AMDGPU_MAX_RINGS; ++i) {
>>   		struct amdgpu_ring *ring = adev->rings[i];
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