Re: Uclamp races due to non-atomic static_branch_likely updates

[Steven Rostedt]

On Wed, 21 Oct 2026 15:34:30 +0200
Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> That simply doesn't work.
> 
> Even *IF* memory stores would propagate instantly (they don't) you can
> still have the boolean swap while in the middle of this state.
> 
> ---
> 
> B = true;
> 
> CPU0			CPU1
> 
>  enqueue
>    if (B)
>      something++;
> 
>      			B = false;
> 
>  dequeue
>    if (B)
>      something--;
> 
> 
> ---
> 
> Will still be left with something unbalanced, even if everything is
> super duper magically atomic.

Fair point.

-- Steve