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

From: Jürgen Groß
Date: Fri Nov 20 2020 - 07:05:22 EST


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 be fine with that. I didn't add something like that because I
couldn't find a suitable CONFIG_ :-)


Juergen

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