Re: [RFC PATCH 00/12] FUTEX_PING: A stealable futex using Proxy Execution.

[Peter Zijlstra]

On Thu, Sep 17, 2026 at 04:33:24AM +0000, Suleiman Souhlal wrote:
> Hello,
> 
> This patch series adds a new type of PI futexes, PI Next Generation,
> or PING (name coined by Steven Rostedt) (but other name suggestions
> are welcome!), that differs from classic PI futexes in that they can
> be stolen from the top waiter, and use Proxy Execution instead of
> rtmutexes internally. 
> 
> The reason to allow the futexes to be stolen is that with classic PI
> futex's strict handoff to the top waiter, new contending lockers are
> now forced to wait in queue, which means that any locking operation
> now becomes a scheduling event. With stealing, a contending locker has
> the chance of taking the lock without blocking. The longer wait time
> of blocked tasks can be mitigated by forcing the lock to be handed
> off to them in a way that can't be stolen, when they've been stolen
> from too much, to ensure they don't get starved.
> 
> The use of Proxy Execution lets us also get Priority Inheritance for
> for fair tasks, which PI futexes don't really allow.

https://patch.msgid.link/1490204338-1856-1-git-send-email-longman%40redhat.com

Also, the goal is to eventually delete rt_mutex and have it be the
normal mutex, in which case the existing FUTEX_*_PI things will
automagically work.

So I'm thinking all of this is way premature.