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

[Jürgen Groß]

On 20.11.20 12:59, Peter Zijlstra wrote:
> 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?

I'd like to, but using WARN_ON_ONCE() in include/asm/irqflags.h sounds
like a perfect receipt for include dependency hell.

We could use a plain asm("ud2") instead.


Juergen

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