linux-kernel - Re: [RFC PATCH 07/86] Revert "livepatch,sched: Add livepatch task switching to cond

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Message-ID: <20231109195649.2b2869fc@gandalf.local.home>
Date:   Thu, 9 Nov 2023 19:56:49 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Josh Poimboeuf <jpoimboe@...nel.org>
Cc:     Ankur Arora <ankur.a.arora@...cle.com>,
        linux-kernel@...r.kernel.org, tglx@...utronix.de,
        peterz@...radead.org, torvalds@...ux-foundation.org,
        paulmck@...nel.org, linux-mm@...ck.org, x86@...nel.org,
        akpm@...ux-foundation.org, luto@...nel.org, bp@...en8.de,
        dave.hansen@...ux.intel.com, hpa@...or.com, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        willy@...radead.org, mgorman@...e.de, jon.grimm@....com,
        bharata@....com, raghavendra.kt@....com,
        boris.ostrovsky@...cle.com, konrad.wilk@...cle.com,
        jgross@...e.com, andrew.cooper3@...rix.com, mingo@...nel.org,
        bristot@...nel.org, mathieu.desnoyers@...icios.com,
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        anton.ivanov@...bridgegreys.com, mattst88@...il.com,
        krypton@...ich-teichert.org, David.Laight@...LAB.COM,
        richard@....at, mjguzik@...il.com, Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org
Subject: Re: [RFC PATCH 07/86] Revert "livepatch,sched: Add livepatch task
 switching to cond_resched()"

On Thu, 9 Nov 2023 09:51:18 -0800
Josh Poimboeuf <jpoimboe@...nel.org> wrote:

> > I guess I'm not fully understanding what the cond rescheds are for. But
> > would an IPI to all CPUs setting NEED_RESCHED, fix it?  
> 
> If all livepatch arches had the ORC unwinder, yes.
> 
> The problem is that frame pointer (and similar) unwinders can't reliably
> unwind past an interrupt frame.

Perhaps we can use this to push those archs with bad unwinders to port over
ORC unwinding ;-)

-- Steve