Re: [RFC PATCH 00/16] x86/split_lock: Enable #AC exception for split locked accesses

[Thomas Gleixner]

On Thu, 21 Jun 2018, Fenghua Yu wrote:
> The control knobs allow sysadmin to handle #AC for split lock in different
> scenarios and usages.
> 
> The control knob for kernel is to choose re-executing the faulting
> instruction (default) or kernel panic. Kernel panic may be useful in hard
> real time which has less tolerant to bad performance.

That's nonsense, really.

 1) The re-executing mechanism is broken and totally useless

 2) Panicing a real-time system just due to a single #AC is total
    overkill. Real-Time systems care very much about proper safe state
    transitioning. Panic is surely a safe state, but so is power off. But
    neither of them qualifies as proper state transitioning.

Thanks,

	tglx