Re: [v2 PATCH] mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct

[Tetsuo Handa]

On 2018/03/27 4:21, Cyrill Gorcunov wrote:
> That said I think using read-lock here would be a bug.

If I understand correctly, the caller can't set both fields atomically, for
prctl() does not receive both fields at one call.

  prctl(PR_SET_MM, PR_SET_MM_ARG_START xor PR_SET_MM_ARG_END xor PR_SET_MM_ENV_START xor PR_SET_MM_ENV_END, new value, 0, 0);

Then, I wonder whether reading arg_start|end and env_start|end atomically makes
sense. Just retry reading if arg_start > env_end or env_start > env_end is fine?