Re: [PATCH 3/3] x86/fpu: Remove init_task FPU state dependencies, add debugging warning

[Oleg Nesterov <oleg@redhat.com>]

On 06/05, Ingo Molnar wrote:
>
> But the init task isn't supposed to be using the FPU in any case,

Afaics, the same is true for any PF_KTHREAD/USER_WORKER thread?

> +#ifdef CONFIG_X86_DEBUG_FPU
> +struct fpu *x86_task_fpu(struct task_struct *task)
> +{
> +	WARN_ON_ONCE(task == &init_task);
> +
> +	return (void *)task + sizeof(*task);
> +}

So perhaps WARN_ON_ONCE(task->flags & PF_KTHREAD) makes more sense?

Although in this case fpu_clone() can't use x86_task_fpu(dst) as I tried
to suggest in reply to 2/3.




This is offtopic right now, but I am wondering if it makes any sense to
make arch_task_struct_size depend on PF_KTHREAD... I mean, create another
task_struct_kthread_cachep used by alloc_task_struct_node() if PF_KTHREAD.

Oleg.