linux-kernel - Re: [Problem] Cache line starvation

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Message-ID: <alpine.DEB.2.21.1809282132530.1432@nanos.tec.linutronix.de>
Date:   Fri, 28 Sep 2018 21:34:09 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
cc:     Kurt Kanzenbach <kurt.kanzenbach@...utronix.de>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org,
        Daniel Wagner <daniel.wagner@...mens.com>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [Problem] Cache line starvation

On Fri, 28 Sep 2018, Sebastian Andrzej Siewior wrote:

> On 2018-09-27 16:47:47 [+0200], Thomas Gleixner wrote:
> > I wonder if it's just the store on the stack which makes it work. I've seen
> > that when instrumenting x86. When the careful instrumentation just stayed
> > in registers it failed. Once it was too much and stack got involved it
> > vanished away.
> 
> Added two load/stores into wait_task_inactive() and it still triggers
> (on the core2duo).

So it was some interaction with rdtsc() which got stored on
stack. Heisenbugs are lovely.

Thanks,

	tglx