Re: [PATCH 1/9] coresight: change coresight_device lock type to raw_spinlock_t

[Steven Rostedt]

On Thu, 28 Nov 2024 07:39:22 +0000
Yeo Reum Yun <YeoReum.Yun@xxxxxxx> wrote:

> Hi Steven,
> 
> > We should start documenting what is not real-time "safe". That is, if this
> > code is executed, we have a loop here that holds a raw spin lock. This
> > appears to make the time the raw spin lock held to be non deterministic.
> > 
> > If someone is running PREEMPT_RT and expects deterministic behavior, they
> > cannot be using this code. That is fine, but we should probably create a
> > document somewhere that notes this.
> >
> > -- Steve  
> 
> I think it's quite deterministic becase the number of loop currently
> determined by the number of preload_feats.
> 
> Also, I don't think the number of  feats will be loaded as much as
> it can do undeterministic behavior since 
> the number is not many and it is quite predictable.

Still should be documented somewhere. It should describe the maximum number
of feats that will ever be loaded. If there's a max, it makes it back to
O(1). With a 'k' of how long it takes to process the max number of feats.

-- Steve