linux-kernel - Re: [PATCH 4/7] drm/amd: kill the outdated "Only the pthreads threading model is supported" checks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: <aTai1a2sFqTh7wv9@redhat.com>
Date: Mon, 8 Dec 2025 11:05:09 +0100
From: Oleg Nesterov <oleg@...hat.com>
To: Christian König <christian.koenig@....com>
Cc: 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>,
	Felix Kuehling <Felix.Kuehling@....com>,
	Alex Deucher <alexander.deucher@....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>,
	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Subject: Re: [PATCH 4/7] drm/amd: kill the outdated "Only the pthreads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 12/08, Christian König wrote:
>
> On 12/7/25 13:39, 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().
>
> Just for my understanding: That is because CLONE_THREAD can only be
> specified together with CLONE_SIGHAND and CLONE_VM, correct?

Yes, copy copy_process() does

	if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND))
		return ERR_PTR(-EINVAL);

	if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM))
		return ERR_PTR(-EINVAL);

	...

	if (clone_flags & CLONE_THREAD) {
		p->group_leader = current->group_leader;
		p->tgid = current->tgid;
	} else {
		p->group_leader = p;
		p->tgid = p->pid;
	}
> Reviewed-by: Christian König <christian.koenig@....com>

Thanks!

> Should we pick that one up or do you want to merge it upstream somehow?

If you don't object, I would like to route this series via -mm tree.

See 0/7, I am going to send more (simple) tree-wide changes which depend
on this series.

Oleg.

> Regards,
> Christian.
>
> > ---
> >  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);
>