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Date: Wed, 22 Nov 2017 10:10:29 -0800
From: Andi Kleen <andi@firstfloor.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andy Lutomirski <luto@amacapital.net>,
        Andi Kleen <andi@firstfloor.org>,
        Peter Zijlstra <peterz@infradead.org>,
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        Michael Kerrisk <mtk.manpages@gmail.com>
Subject: Re: [RFC PATCH for 4.15 v12 00/22] Restartable sequences and CPU op
 vector
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> > If anyone ever reports that as a problem, I'll gladly fix it in the
> > kernel.  That's doable without an ABI change.  If rseq-like things
> > started breaking single-stepping, we can't just fix it in the kernel.

AFAIK nobody ever complained about it since we have vsyscalls and vDSOs.

> 
> Very true. And rseq does break both line-level and instruction-level
> single-stepping.

They can just set a break point after it and continue.

In fact it could be even expressed to the debugger to do
that automatically based on some dwarf extension.

I also disagree that opv somehow "solves" debugging: it's a completely
different code path that has nothing to do with the original code path.
That's not debugging, that's at best a workaround. I don't think it's
any better than the break point method.

-Andi