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Date:   Mon, 20 Jan 2020 08:27:25 -0800
From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Marco Elver <elver@google.com>, andreyknvl@google.com,
        glider@google.com, dvyukov@google.com, kasan-dev@googlegroups.com,
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        viro@zeniv.linux.org.uk, christophe.leroy@c-s.fr, dja@axtens.net,
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        daniel@iogearbox.net, cyphar@cyphar.com, keescook@chromium.org,
        linux-arch@vger.kernel.org
Subject: Re: [PATCH 3/5] asm-generic, kcsan: Add KCSAN instrumentation for
 bitops
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On Mon, Jan 20, 2020 at 03:40:48PM +0100, Peter Zijlstra wrote:
> On Mon, Jan 20, 2020 at 03:19:25PM +0100, Marco Elver wrote:
> > Add explicit KCSAN checks for bitops.
> > 
> > Note that test_bit() is an atomic bitop, and we instrument it as such,
> 
> Well, it is 'atomic' in the same way that atomic_read() is. Both are
> very much not atomic ops, but are part of an interface that facilitates
> atomic operations.

True, but they all are either inline assembly or have either an
implicit or explicit cast to volatile, so they could be treated
the same as atomic_read(), correct?  If not, what am I missing?

(There is one exception, but it is in arch/x86/boot/bitops.h,
which I UP-only, correct?)

						Thanx, Paul