Re: [PATCH 2/8] kernel/fork: Duplicate task_struct before stack allocation.

[Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>]

On 2022-02-11 15:42:38 [-0800], Andy Lutomirski wrote:
> On 1/25/22 07:26, Sebastian Andrzej Siewior wrote:
> > alloc_thread_stack_node() already populates the task_struct::stack
> > member except on IA64. The stack pointer is saved and populated again
> > because IA64 needs it and arch_dup_task_struct() overwrites it.
> 
> I understand the problem, I think.
> 
> > 
> > Allocate thread's stack after task_struct has been duplicated as a
> > preparation.
> > 
> 
> But I don't understand this.  How does this patch relate to the problem?

So I duplicate the task-struct, assign the stack pointer in
alloc_thread_stack_node() with no need to update the stack pointer
later. Otherwise arch_dup_task_struct() would reset the pointer.

> Also, you appear to be missing a change to the free_stack and free_tsk code
> at the end of dup_task_struct().

It looks right. What am I missing?

Sebastian