Re: [PATCH] x86/entry/64: Context-track syscalls before enabling interrupts

From: Ingo Molnar
Date: Fri Aug 21 2015 - 03:50:43 EST



* Frederic Weisbecker <fweisbec@xxxxxxxxx> wrote:

> > I want to have a real hook to call that says "switch to IRQ context from
> > CONTEXT_USER" or "switch to IRQ context from CONTEXT_KERNEL" (aka noop), but
> > that doesn't currently exist.
>
> You're not answering _why_ you want that.

So we'd have a comprehensive, 100% coverage, self-sufficient set of callbacks that
track the kernel's current context state at the points where the context switches
actually occur - not just something cobbled together heterogenously. The low level
x86 asm code was rather messy in this area, better organization would be welcome,
I don't think we can overdo it.

( I'm assuming here that it can all be done for zero or negative cost, and that
the result will be correct and won't hurt existing users in any fashion. )

Thanks,

Ingo
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