Re: [PATCH 13/18] exec: make exec path waiting for mmap_sem killable

[Oleg Nesterov]

On 02/29, Michal Hocko wrote:
>
> @@ -267,7 +267,10 @@ static int __bprm_mm_init(struct linux_binprm *bprm)
>  	if (!vma)
>  		return -ENOMEM;
>  
> -	down_write(&mm->mmap_sem);
> +	if (down_write_killable(&mm->mmap_sem)) {
> +		err = -EINTR;
> +		goto err_free;
> +	}
>  	vma->vm_mm = mm;

I won't argue, but this looks unnecessary. Nobody else can see this new mm,
down_write() can't block.

In fact I think we can just remove down_write/up_write here. Except perhaps
there is lockdep_assert_held() somewhere in these paths.

Oleg.