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Date: Mon, 20 Jan 2020 17:52:23 +0100 From: Peter Zijlstra <peterz@...radead.org> To: "Paul E. McKenney" <paulmck@...nel.org> Cc: Marco Elver <elver@...gle.com>, andreyknvl@...gle.com, glider@...gle.com, dvyukov@...gle.com, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org, mark.rutland@....com, will@...nel.org, boqun.feng@...il.com, arnd@...db.de, viro@...iv.linux.org.uk, christophe.leroy@....fr, dja@...ens.net, mpe@...erman.id.au, rostedt@...dmis.org, mhiramat@...nel.org, mingo@...nel.org, christian.brauner@...ntu.com, daniel@...earbox.net, cyphar@...har.com, keescook@...omium.org, linux-arch@...r.kernel.org Subject: Re: [PATCH 3/5] asm-generic, kcsan: Add KCSAN instrumentation for bitops On Mon, Jan 20, 2020 at 08:27:25AM -0800, Paul E. McKenney wrote: > 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? Sure, but that is due to instrumentation requirements, not anything else. Also note the distinct lack of __test_bit(), to mirror the non-atomic __set_bit() and __clear_bit().
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