linux-kernel - Re: [PATCH 4/7] drm/amd: kill the outdated "Only the pthreads threading model is supported" checks

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Message-ID: <8bf372ab-2625-4f87-a8e8-7a1bc9debcc5@amd.com>
Date: Tue, 9 Dec 2025 14:23:53 -0500
From: Felix Kuehling <felix.kuehling@....com>
To: Oleg Nesterov <oleg@...hat.com>, Todd Kjos <tkjos@...roid.com>,
 Martijn Coenen <maco@...roid.com>, Joel Fernandes <joelagnelf@...dia.com>,
 Christian Brauner <brauner@...nel.org>, Carlos Llamas <cmllamas@...gle.com>,
 Suren Baghdasaryan <surenb@...gle.com>,
 Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Boris Brezillon <boris.brezillon@...labora.com>,
 Rob Herring <robh@...nel.org>, Steven Price <steven.price@....com>,
 Adrián Larumbe <adrian.larumbe@...labora.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Liviu Dudau <liviu.dudau@....com>, Jason Gunthorpe <jgg@...pe.ca>,
 Leon Romanovsky <leon@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>
Cc: linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
 dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH 4/7] drm/amd: kill the outdated "Only the pthreads
 threading model is supported" checks

On 2025-12-07 07:39, Oleg Nesterov wrote:
> Nowaday task->group_leader->mm != task->mm is only possible if
> a) task is not a group leader and b) task->group_leader->mm == NULL
> because task->group_leader has already exited using sys_exit().
>
> I don't think that drm/amd tries to detect/nack this case.
>
> Signed-off-by: Oleg Nesterov <oleg@...hat.com>

Acked-by: Felix Kuehling <felix.kuehling@....com>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c   |  3 ---
>   drivers/gpu/drm/amd/amdkfd/kfd_process.c | 10 ----------
>   2 files changed, 13 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> index a0f8ba382b9e..e44f158a11f0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
> @@ -2551,9 +2551,6 @@ void amdgpu_vm_set_task_info(struct amdgpu_vm *vm)
>   	vm->task_info->task.pid = current->pid;
>   	get_task_comm(vm->task_info->task.comm, current);
>   
> -	if (current->group_leader->mm != current->mm)
> -		return;
> -
>   	vm->task_info->tgid = current->tgid;
>   	get_task_comm(vm->task_info->process_name, current->group_leader);
>   }
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> index a085faac9fe1..f8ef18a3aa71 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
> @@ -833,12 +833,6 @@ struct kfd_process *kfd_create_process(struct task_struct *thread)
>   	if (!(thread->mm && mmget_not_zero(thread->mm)))
>   		return ERR_PTR(-EINVAL);
>   
> -	/* Only the pthreads threading model is supported. */
> -	if (thread->group_leader->mm != thread->mm) {
> -		mmput(thread->mm);
> -		return ERR_PTR(-EINVAL);
> -	}
> -
>   	/* If the process just called exec(3), it is possible that the
>   	 * cleanup of the kfd_process (following the release of the mm
>   	 * of the old process image) is still in the cleanup work queue.
> @@ -918,10 +912,6 @@ struct kfd_process *kfd_get_process(const struct task_struct *thread)
>   	if (!thread->mm)
>   		return ERR_PTR(-EINVAL);
>   
> -	/* Only the pthreads threading model is supported. */
> -	if (thread->group_leader->mm != thread->mm)
> -		return ERR_PTR(-EINVAL);
> -
>   	process = find_process(thread, false);
>   	if (!process)
>   		return ERR_PTR(-EINVAL);