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Date:   Mon, 9 Sep 2019 16:21:11 +1000
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     torvalds@linux-foundation.org, mathieu.desnoyers@efficios.com,
        tglx@linutronix.de, joel@joelfernandes.org,
        stern@rowland.harvard.edu, rostedt@goodmis.org,
        valentin.schneider@arm.com, linux-kernel@vger.kernel.org,
        paulmck@linux.ibm.com, boqun.feng@gmail.com, will.deacon@arm.com,
        dhowells@redhat.com
Subject: Re: [PATCH 1/1] Fix: trace sched switch start/stop racy updates
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Peter Zijlstra <peterz@infradead.org> wrote:
>
> Paulmck actually has an example of that somewhere; ISTR that particular
> case actually got fixed by GCC, but I'd really _love_ for some compiler
> people (both GCC and LLVM) to state that their respective compilers will
> not do load/store tearing for machine word sized load/stores.
> 
> Without this written guarantee (which supposedly was in older GCC
> manuals but has since gone missing), I'm loathe to rely on it.

IIRC in that case gcc actually broke atomic writes even with a
volatile keyword.  So even WRITE_ONCE wouldn't have saved us.

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
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