Re: [RFC][PATCH] prctl: Add PR_SET_TIMERSLACK_PID for setting timer slack of an arbitrary thread.

[Arjan van de Ven <arjan@linux.intel.com>]

On 6/25/2015 4:24 PM, John Stultz wrote:
> From: Ruchi Kandoi <kandoiruchi@google.com>
>
> This patch has been in the Android tree for ahwile, and I've not
> seen it posted for review. Unfortunately the PR_SET_TIMERSLACK_PID
> value has collided many times w/ upstream (first w/
> PR_SET_THP_DISABLE, and again w/ PR_MPX_ENABLE_MANAGEMENT).
>
> So to try to avoid further ABI trouble, I wanted to send this out
> for initial review to see if there were any major objections,
> or ideas for alternative approaches.
>
> Thoughts and feedback would be appreciated.

I am wondering if it would be more natural to make this a cgroup
property.. and have a way for threads to inherit their cgroup
effective value.

it'll fit more natural in many places than just a per pid setting.
(I have nothing against it per se other than that I think the
security check is wrong; I fully expected to be on the level of
ptrace_may_access(PTRACE_MODE_ATTACH) or the like.. not just NICE.
you can seriously change task behavior with this by setting a 4 second
value or so.. much more than just with nice)