Re: [PATCH v2 05/12] x86: rework arch_local_irq_restore() to not use popf

[Peter Zijlstra <peterz@xxxxxxxxxxxxx>]

On Fri, Nov 20, 2020 at 12:46:23PM +0100, Juergen Gross wrote:
> +static __always_inline void arch_local_irq_restore(unsigned long flags)
> +{
> +     if (!arch_irqs_disabled_flags(flags))
> +             arch_local_irq_enable();
> +}

If someone were to write horrible code like:

        local_irq_disable();
        local_irq_save(flags);
        local_irq_enable();
        local_irq_restore(flags);

we'd be up some creek without a paddle... now I don't _think_ we have
genius code like that, but I'd feel saver if we can haz an assertion in
there somewhere...

Maybe something like:

#ifdef CONFIG_DEBUG_ENTRY // for lack of something saner
        WARN_ON_ONCE((arch_local_save_flags() ^ flags) & X86_EFLAGS_IF);
#endif

At the end?