From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>
Subject: Re: [RFC PATCH for 4.15 v12 00/22] Restartable sequences and CPU op
 vector
Date: Wed, 22 Nov 2017 10:10:29 -0800
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To: Mathieu Desnoyers <mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org>
Cc: Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>, Andi Kleen <andi-Vw/NltI1exuRpAAqCnN02g@public.gmane.org>, Peter Zijlstra <peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, "Paul E. McKenney" <paulmck-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Boqun Feng <boqun.feng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Dave Watson <davejwatson-b10kYP2dOMg@public.gmane.org>, linux-kernel <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, linux-api <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Paul Turner <pjt-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Russell King <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>, Andrew Hunter <ahh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, Chris Lameter <cl-vYTEC60ixJUAvxtiuMwx3w@public.gmane.org>, Ben Maurer <bmaurer-b10kYP2dOMg@public.gmane.org>, rostedt <rostedt-nx8X9YLhiw1AfugRpC6u6w@public.gmane.org>, Josh Triplett <josh-iaAMLnmF4UmaiuxdJuQwMA@public.gmane.org>, Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Catalin
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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