From: Peter Zijlstra <peterz@infradead.org>
To: "Reshetova, Elena" <elena.reshetova@intel.com>
Cc: Alan Stern <stern@rowland.harvard.edu>,
Dmitry Vyukov <dvyukov@google.com>,
Andrea Parri <andrea.parri@amarulasolutions.com>,
Kees Cook <keescook@chromium.org>,
"Paul E. McKenney" <paulmck@linux.ibm.com>,
Will Deacon <will.deacon@arm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Andrey Ryabinin <aryabinin@virtuozzo.com>,
Anders Roxell <anders.roxell@linaro.org>,
Mark Rutland <mark.rutland@arm.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] kcov: convert kcov.refcount to refcount_t
Date: Mon, 28 Jan 2019 10:28:00 +0100 [thread overview]
Message-ID: <20190128092800.GE28467@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <2236FBA76BA1254E88B949DDB74E612BA4B944B3@IRSMSX102.ger.corp.intel.com>
On Sun, Jan 27, 2019 at 06:41:38PM +0000, Reshetova, Elena wrote:
> > On Mon, Jan 21, 2019 at 11:05:03AM -0500, Alan Stern wrote:
> > > On Mon, 21 Jan 2019, Peter Zijlstra wrote:
> > Yes, that's a very good suggestion.
> >
> > I suppose we can add smp_acquire__after_ctrl_dep() on the true branch.
> > Then it reall does become rel_acq.
> >
> > A wee something like so (I couldn't find an arm64 refcount, even though
> > I have distinct memories of talk about it).
> >
> > This isn't compiled, and obviously needs comment/documentation updates
> > to go along with it.
> >
> > ---
> > arch/x86/include/asm/refcount.h | 9 ++++++++-
> > lib/refcount.c | 7 ++++++-
> > 2 files changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/refcount.h b/arch/x86/include/asm/refcount.h
> > index dbaed55c1c24..6f7a1eb345b4 100644
> > --- a/arch/x86/include/asm/refcount.h
> > +++ b/arch/x86/include/asm/refcount.h
> > @@ -74,9 +74,16 @@ bool refcount_sub_and_test(unsigned int i, refcount_t *r)
> >
> > static __always_inline __must_check bool refcount_dec_and_test(refcount_t *r)
> > {
> > - return GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl",
> > + bool ret = GEN_UNARY_SUFFIXED_RMWcc(LOCK_PREFIX "decl",
> >
> > REFCOUNT_CHECK_LT_ZERO,
> > r-
> > >refs.counter, e, "cx");
> > +
> > + if (ret) {
> > + smp_acquire__after_ctrl_dep();
> > + return true;
> > + }
> > +
> > + return false;
> > }
>
> Actually as I started to do this, any reason why the change here only
> for dec_and_test and not for sub_and _test also? Should not the arch.
> specific logic follow the generic?
Yes, sub_and_test also needs it; I simply overlooked it.
next prev parent reply other threads:[~2019-01-28 9:28 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 10:27 [PATCH] kcov: convert kcov.refcount to refcount_t Elena Reshetova
2019-01-16 12:51 ` Dmitry Vyukov
2019-01-21 9:52 ` Dmitry Vyukov
2019-01-21 11:45 ` Andrea Parri
2019-01-21 12:29 ` Dmitry Vyukov
2019-01-21 14:44 ` Andrea Parri
2019-01-21 13:18 ` Peter Zijlstra
2019-01-21 16:05 ` Alan Stern
2019-01-21 17:00 ` Dmitry Vyukov
2019-01-22 9:04 ` Peter Zijlstra
2019-01-22 23:22 ` Kees Cook
2019-01-25 9:02 ` Reshetova, Elena
2019-01-25 10:31 ` Peter Zijlstra
2019-01-27 18:41 ` Reshetova, Elena
2019-01-28 8:33 ` Dmitry Vyukov
2019-01-28 9:28 ` Peter Zijlstra [this message]
2019-01-21 11:51 ` Andrea Parri
2019-01-21 12:38 ` Mark Rutland
2019-01-21 12:42 ` Dmitry Vyukov
2019-01-21 14:07 ` Reshetova, Elena
2019-01-21 17:07 ` Dmitry Vyukov
2019-01-31 10:03 ` Reshetova, Elena
2019-01-31 10:06 ` Dmitry Vyukov
2019-01-31 10:09 ` Reshetova, Elena
2019-01-31 10:33 ` Dmitry Vyukov
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