linux-kernel - Re: [stable 4.19] [PANIC]: tracing: Centralize preemptirq tracepoints and unify their usage

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Date:   Mon, 5 Oct 2020 15:18:33 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Namhyung Kim <namhyung@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux- stable <stable@...r.kernel.org>,
        Sasha Levin <sashal@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        LTP List <ltp@...ts.linux.it>, lkft-triage@...ts.linaro.org
Subject: Re: [stable 4.19] [PANIC]: tracing: Centralize preemptirq
 tracepoints and unify their usage

On Fri, Sep 25, 2020 at 11:30:49AM -0400, Steven Rostedt wrote:
> On Fri, 25 Sep 2020 17:12:45 +0200
> Greg Kroah-Hartman <gregkh@...uxfoundation.org> wrote:
> 
> > > Specifically, commits:
> > > 
> > > a0d14b8909de55139b8702fe0c7e80b69763dcfb ("x86/mm, tracing: Fix CR2 corruption")
> > > 6879298bd0673840cadd1fb36d7225485504ceb4 ("x86/entry/64: Prevent clobbering of saved CR2 value")
> > > b8f70953c1251d8b16276995816a95639f598e70 ("x86/entry/32: Pass cr2 to do_async_page_fault()")
> > > 
> > > (which are in 5.4 but not 4.19)
> > > 
> > > But again, is this too intrusive. There was a workaround that was
> > > original proposed, but Peter didn't want any more band-aids, and did
> > > the restructuring, but as you can see from the two other patches, it
> > > makes it a bit more high risk.  
> > 
> > If those are known to work, why can't I take them as-is?
> 
> If they apply without tweaks, I say "Go for it" ;-)
> 
> My worry is that they may have other unknown dependencies. And I only
> looked at what was applied between 4.19 and 5.4 mainline. I haven't
> looked at what else may have been backported to fix the above three
> commits.

I tried to backport the above series, and quickly gave up, as yes, you
are right, the dependencies are deep and messy from what I can tell.

WHat's wrong with just moving to 5.4? :)

thanks,

greg k-h