Re: [PATCH] drm/amdgpu: Add trace events for pid register/deregister

On 28-07-2026 06:45 pm, Francis, David wrote:
>> This function is called from many places and will not match when a
>> process start and similarly for stop. Better find a unique function,
>> also this will be called for KGD and KFD processes too.
> This function is called when the last ref to an task_info is put.
> Many places in the code temporarily acquire references to a task_info
> but only amdgpu_vm holds the long-term reference, acquired in
> amdgpu_vm_create_task_info and relased in amdgpu_vm_fini.
>
> Tying the trace to the lifetime of task_info also guarantees that
> there will be exactly one such trace for each task_info, matching
> the register trace semantics

For begining, amdgpu_vm_init sounds like a better choice
for ending, amdgpu_vm_destroy_task_info is correct.

Regards
Sunil Khatri

>
> David Francis
>
>
> ________________________________________
> From: Khatri, Sunil <[email protected]>
> Sent: Tuesday, July 28, 2026 8:26 AM
> To: Francis, David; [email protected]
> Cc: Liu, Shuzhou (Bill); Khatri, Sunil
> Subject: Re: [PATCH] drm/amdgpu: Add trace events for pid register/deregister
>
>
> On 24-07-2026 06:51 pm, David Francis wrote:
>> Some debugging applications need to track when a process starts
>> or stops using the amdgpu driver. For those processes, add ftrace
>> events that track when a amdgpu_vm task info is changed or destroyed.
>>
>> Signed-off-by: David Francis <[email protected]>
>> ---
>>    drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h | 17 +++++++++++++++++
>>    drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c    |  7 +++++++
>>    2 files changed, 24 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h
>> index 5324030a13f5..c79604b9dda1 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_trace.h
>> @@ -732,6 +732,23 @@ TRACE_EVENT(amdgpu_userq_state_changed,
>>                      __entry->client_id, __entry->queue_type, __entry->doorbell_index, __entry->to)
>>    );
>>
>> +TRACE_EVENT(amdgpu_register_pid,
>> +     TP_PROTO(uint32_t pid),
>> +     TP_ARGS(pid),
>> +     TP_STRUCT__entry(__field(uint32_t, pid)),
>> +     TP_fast_assign(__entry->pid = pid;),
>> +     TP_printk("amdgpu register pid %d",
>> +               __entry->pid)
>> +);
>> +TRACE_EVENT(amdgpu_deregister_pid,
>> +     TP_PROTO(uint32_t pid),
>> +     TP_ARGS(pid),
>> +     TP_STRUCT__entry(__field(uint32_t, pid)),
>> +     TP_fast_assign(__entry->pid = pid;),
>> +     TP_printk("amdgpu deregister pid %d",
>> +               __entry->pid)
>> +);
>> +
>>    #undef AMDGPU_JOB_GET_TIMELINE_NAME
>>    #endif
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> index aac8ace9d7a6..8d31a61e8c26 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
>> @@ -2457,6 +2457,9 @@ static void amdgpu_vm_destroy_task_info(struct kref *kref)
>>    {
>>        struct amdgpu_task_info *ti = container_of(kref, struct amdgpu_task_info, refcount);
>>
>> +     if (ti->task.pid)
>> +             trace_amdgpu_deregister_pid(ti->task.pid);
>> +
>>        kfree(ti);
>>    }
>>
>> @@ -2543,6 +2546,10 @@ void amdgpu_vm_set_task_info(struct amdgpu_vm *vm)
> This function is called from many places and will not match when a
> process start and similarly for stop. Better find a unique function,
> also this will be called for KGD and KFD processes too.
> Chose a better function to add the trace although trace in itself is fine.
>
> Regards
> Sunil Khatri
>>        if (vm->task_info->task.pid == current->pid)
>>                return;
>>
>> +     if (vm->task_info->task.pid)
>> +             trace_amdgpu_deregister_pid(vm->task_info->task.pid);
>> +     trace_amdgpu_register_pid(current->pid);
>> +
>>        vm->task_info->task.pid = current->pid;
>>        get_task_comm(vm->task_info->task.comm, current);
>>