From: Kees Cook <keescook@chromium.org>
To: Jeff Layton <jlayton@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jann Horn <jannh@google.com>,
linux-hardening@vger.kernel.org,
Elena Reshetova <elena.reshetova@intel.com>,
David Windsor <dwindsor@gmail.com>,
Hans Liljestrand <ishkamiel@gmail.com>,
Trond Myklebust <trond.myklebust@hammerspace.com>,
Anna Schumaker <anna@kernel.org>,
Chuck Lever <chuck.lever@oracle.com>, Neil Brown <neilb@suse.de>,
Olga Kornievskaia <kolga@netapp.com>,
Dai Ngo <Dai.Ngo@oracle.com>, Tom Talpey <tom@talpey.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
Alexey Gladkov <legion@kernel.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Yu Zhao <yuzhao@google.com>,
linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org,
netdev@vger.kernel.org
Subject: Re: [PATCH v2] creds: Convert cred.usage to refcount_t
Date: Fri, 18 Aug 2023 13:24:58 -0700 [thread overview]
Message-ID: <202308181317.66E6C9A5@keescook> (raw)
In-Reply-To: <e5234e7bd9fbd2531b32d64bc7c23f4753401cee.camel@kernel.org>
On Fri, Aug 18, 2023 at 04:10:49PM -0400, Jeff Layton wrote:
> [...]
> extra checks (supposedly) compile down to nothing. It should be possible
> to build alternate refcount_t handling functions that are just wrappers
> around atomic_t with no extra checks, for folks who want to really run
> "fast and loose".
No -- there's no benefit for this. We already did all this work years
ago with the fast vs full break-down. All that got tossed out since it
didn't matter. We did all the performance benchmarking and there was no
meaningful difference -- refcount _is_ atomic with an added check that
is branch-predicted away. Peter Zijlstra and Will Deacon spent a lot of
time making it run smoothly. :)
-Kees
--
Kees Cook
next prev parent reply other threads:[~2023-08-18 20:25 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-18 4:17 [PATCH v2] creds: Convert cred.usage to refcount_t Kees Cook
2023-08-18 17:55 ` Andrew Morton
2023-08-18 18:17 ` Jann Horn
2023-08-18 18:48 ` Kees Cook
2023-08-18 19:31 ` Andrew Morton
2023-08-18 20:10 ` Jeff Layton
2023-08-18 20:24 ` Kees Cook [this message]
2023-08-18 21:07 ` Eric W. Biederman
2023-08-21 10:18 ` David Laight
2023-08-18 20:16 ` Kees Cook
2023-08-18 20:54 ` Jann Horn
2023-08-18 18:46 ` Kees Cook
2023-08-18 20:21 ` David Windsor
2023-08-18 20:12 ` Jeff Layton
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