linux-kernel - Re: [RFR] Store tearing

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Message-ID: <20181029051602.GA3358@andrea>
Date:   Mon, 29 Oct 2018 06:16:02 +0100
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     "Paul E. McKenney" <paulmck@...ux.ibm.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Josh Triplett <josh@...htriplett.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFR] Store tearing

On Sun, Oct 28, 2018 at 06:20:42PM -0700, Paul E. McKenney wrote:
> On Mon, Oct 29, 2018 at 12:10:03AM +0100, Andrea Parri wrote:
> > Hopefully, with Paul's proper email address this time,
> > 
> >   Andrea
> > 
> > On Mon, Oct 29, 2018 at 12:06:27AM +0100, Andrea Parri wrote:
> > > Hi,
> > > 
> > > memory-barriers.txt says:
> > > 
> > >   [on "store tearing"]
> > > 
> > >   "In fact, a recent bug (since fixed) caused GCC to incorrectly use
> > >    this optimization in a volatile store.".
> > > 
> > > I was wondering if you could help me retrieve some reference/discussions
> > > about this?
> 
> This was quite some time ago, but it involved a 32-bit volatile store
> of a constant such as 0x10001.  The machine in question had a narrow
> store-immediate instruction, so the compiler emitted  a pair of 16-bit
> store-immediate instructions.  This bug was fixed, though only after
> significant screaming and shouting.

That does sound like an interesting discussion. ;D  Thanks for the info,

  Andrea


> 
> 							Thanx, Paul
>