From: David Sterba <dsterba@suse.cz>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-kernel@vger.kernel.org, Will Deacon <will.deacon@arm.com>,
Kees Cook <keescook@chromium.org>,
Boqun Feng <boqun.feng@gmail.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>
Subject: Re: [PATCH] refcount: always allow checked forms
Date: Wed, 4 Jul 2018 10:46:41 +0200 [thread overview]
Message-ID: <20180704084641.GL3126@suse.cz> (raw)
In-Reply-To: <20180703100102.16615-1-mark.rutland@arm.com>
On Tue, Jul 03, 2018 at 11:01:02AM +0100, Mark Rutland wrote:
> In many cases, it would be useful to be able to use the full
> sanity-checked refcount helpers regardless of CONFIG_REFCOUNT_FULL, as
> this would help to avoid duplicate warnings where callers try to
> sanity-check refcount manipulation.
>
> This patch refactors things such that the full refcount helpers were
> always built, as refcount_${op}_checked(), such that they can be used
> regardless of CONFIG_REFCOUNT_FULL. This will allow code which *always*
> wants a checked refcount to opt-in, avoiding the need to duplicate the
> logic for warnings.
>
> There should be no functional change as a result of this patch.
>
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: David Sterba <dsterba@suse.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Will Deacon <will.deacon@arm.com>
I dare to give it my
Reviewed-by: David Sterba <dsterba@suse.com>
as my POC implementations were crap and Mark's version is much better.
> ---
> include/linux/refcount.h | 27 +++++++++++++++++-------
> lib/refcount.c | 53 +++++++++++++++++++++++-------------------------
> 2 files changed, 45 insertions(+), 35 deletions(-)
>
> Dave pointed out that it would be useful to be able to opt-in to full checks
> regardless of CONFIG_REFCOUNT_FULL, so that we can simplify callsites where we
> always want checks. I've spotted a few of these in code which is still awaiting
> conversion.
The motivation was code like
WARN_ON(refcount_read(&ref));
if (refcount_dec_and_test(&ref)) { ... }
so the warning is redundant for REFCOUNT_FULL, but I'm going to use the
_checked versions everywhere the performance of refcounts is not
critical.
next prev parent reply other threads:[~2018-07-04 8:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-03 10:01 [PATCH] refcount: always allow checked forms Mark Rutland
2018-07-03 10:33 ` Andrea Parri
2018-07-03 11:39 ` Mark Rutland
2018-07-03 18:30 ` Kees Cook
2018-07-11 5:44 ` Mark Rutland
2018-07-04 8:46 ` David Sterba [this message]
2018-07-11 5:49 ` Mark Rutland
2018-07-11 17:37 ` David Sterba
2018-07-12 12:08 ` Mark Rutland
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