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Date:   Fri, 16 Aug 2019 21:41:52 -0400 (EDT)
From:   Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
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        "Joel Fernandes, Google" <joel@joelfernandes.org>,
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        linux-kernel <linux-kernel@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        paulmck <paulmck@linux.ibm.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Will Deacon <will.deacon@arm.com>,
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Subject: Re: [PATCH 1/1] Fix: trace sched switch start/stop racy updates
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----- On Aug 16, 2019, at 6:57 PM, Linus Torvalds torvalds@linux-foundation.org wrote:

> So in general, we very much expect the compiler to do sane code
> generation, and not (for example) do store tearing on normal
> word-sized things or add writes that weren't there originally etc.

My understanding of https://lwn.net/Articles/793253/ section "Store tearing"
which points at https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56028 seems
to contradict your expectation at least when writing constants to a
64-bit word without a volatile access.

Thanks,

Mathieu


-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com