linux-kernel - Re: [PATCH 1/1] Fix: trace sched switch start/stop racy updates

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Message-ID: <20190820205252.GY28441@linux.ibm.com>
Date:   Tue, 20 Aug 2019 13:52:52 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Joel Fernandes <joel@...lfernandes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alan Stern <stern@...land.harvard.edu>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        rostedt <rostedt@...dmis.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Will Deacon <will.deacon@....com>,
        David Howells <dhowells@...hat.com>
Subject: Re: [PATCH 1/1] Fix: trace sched switch start/stop racy updates

On Tue, Aug 20, 2019 at 10:39:39PM +0200, Peter Zijlstra wrote:
> On Tue, Aug 20, 2019 at 01:31:35PM -0700, Paul E. McKenney wrote:
> > On Tue, Aug 20, 2019 at 04:01:16PM +0200, Peter Zijlstra wrote:
> 
> > > We really should get the compiler folks to give us a
> > > -fno-pointer-provenance. Waiting on the standards committee to get their
> > > act together seems unlikely, esp. given that some people actually seem
> > > to _want_ this nonsense :/
> > 
> > The reason that they want it is to enable some significant optimizations
> > in numerical code on the one hand and in heavily templated C++ code on
> > the other.  Neither of which has much bearing on kernel code.
> > 
> > Interested in coming to the next C standards committee meeting in October
> > to help me push for this?  ;-)
> 
> How about we try and get some compiler folks together at plumbers and
> bribe them with beer? Once we have our compiler knob, we happy :-)

C'mon, Peter!  Where is your sense of self-destruction???  ;-)

But yes, if nothing else there is a Toolchains MC [1].  Which happens to
have a topic entitled "Potential impact/benefit/detriment of recently
developed GCC optimizations on the kernel", now that you mention it.
Looking forward to seeing you in Lisbon!

						Thanx, Paul

[1] https://linuxplumbersconf.org/event/4/sessions/45/#20190909