linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
	torvalds@linux-foundation.org, mark.rutland@arm.com,
	dhowells@redhat.com, linux-arch@vger.kernel.org,
	will.deacon@arm.com, Pablo Neira Ayuso <pablo@netfilter.org>,
	Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
	Florian Westphal <fw@strlen.de>,
	"David S. Miller" <davem@davemloft.net>,
	netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
	netdev@vger.kernel.org
Subject: Re: [PATCH RFC tip/core/rcu 14/15] netfilter: Remove now-redundant smp_read_barrier_depends()
Date: Tue, 10 Oct 2017 10:43:34 +0200	[thread overview]
Message-ID: <20171010084334.nbyhryiwyrl6km4u@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1507594969-8347-14-git-send-email-paulmck@linux.vnet.ibm.com>

On Mon, Oct 09, 2017 at 05:22:48PM -0700, Paul E. McKenney wrote:
> READ_ONCE() now implies smp_read_barrier_depends(), which means that
> the instances in arpt_do_table(), ipt_do_table(), and ip6t_do_table()
> are now redundant.  This commit removes them and adjusts the comments.

Similar to the previous patch, the lack of READ_ONCE() in the original
code is a pre-existing bug. It would allow the compiler to tear the load
and observe a composite of two difference pointer values, or reload the
private pointer and result in table_base and jumpstacl being part of
different objects.

It would be good to point out this actually fixes a bug in the code.

  reply	other threads:[~2017-10-10  8:44 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-10  0:19 [PATCH RFC tip/core/rcu 0/15] Remove to-be-unneeded smp_read_barrier_depends() Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 01/15] doc: READ_ONCE() now implies smp_barrier_depends() Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 02/15] mn10300: READ_ONCE() now implies smp_read_barrier_depends() Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 03/15] drivers/net/ethernet/qlogic/qed: Fix __qed_spq_block() ordering Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 04/15] fs/dcache: Use release-acquire for name/length update Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 05/15] percpu: READ_ONCE() now implies smp_read_barrier_depends() Paul E. McKenney
2017-10-10 14:08   ` Tejun Heo
2017-10-10 15:30     ` Paul E. McKenney
2017-10-10 15:49       ` Tejun Heo
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 06/15] rcu: Adjust read-side accessor comments for READ_ONCE() Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 07/15] rtnetlink: Update now-misleading smp_read_barrier_depends() comment Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 08/15] seqlock: Remove now-redundant smp_read_barrier_depends() Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 09/15] uprobes: " Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 10/15] locking: Remove smp_read_barrier_depends() from queued_spin_lock_slowpath() Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 11/15] tracepoint: Remove smp_read_barrier_depends() from comment Paul E. McKenney
2017-10-10  0:31   ` Steven Rostedt
2017-10-10  1:12     ` Mathieu Desnoyers
2017-10-10 15:32       ` Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 12/15] lib/assoc_array: Remove smp_read_barrier_depends() Paul E. McKenney
2017-10-10  8:39   ` Peter Zijlstra
2017-10-10  9:36   ` David Howells
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 13/15] mm/ksm: Remove now-redundant smp_read_barrier_depends() Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 14/15] netfilter: " Paul E. McKenney
2017-10-10  8:43   ` Peter Zijlstra [this message]
2017-10-10 15:56     ` Paul E. McKenney
2017-10-10  0:22 ` [PATCH RFC tip/core/rcu 15/15] keyring: " Paul E. McKenney
2017-10-10  9:35 ` [PATCH RFC tip/core/rcu 12/15] lib/assoc_array: Remove smp_read_barrier_depends() David Howells
2017-10-10 15:50   ` Paul E. McKenney
2017-10-10 15:54     ` Peter Zijlstra
2017-10-10 16:05       ` Paul E. McKenney
2017-10-11 12:19   ` David Howells
2017-10-11 12:22     ` Will Deacon
2017-10-11 12:54       ` Paul E. McKenney
2017-10-11 14:18         ` Will Deacon
2017-10-11 14:50           ` Paul E. McKenney
2017-10-11 12:58     ` Paul E. McKenney
2017-10-11 15:17     ` David Howells
2017-10-11 15:59       ` Paul E. McKenney
2017-10-11 16:12         ` Peter Zijlstra
2017-10-11 16:24           ` Peter Zijlstra
2017-10-11 16:47             ` Paul E. McKenney
2017-10-11 16:54               ` Peter Zijlstra
2017-10-11 17:06                 ` Paul E. McKenney
2017-10-11 17:11                   ` Peter Zijlstra
2017-10-11 17:34                     ` Paul E. McKenney
2017-10-11 18:43                       ` Dmitry Vyukov
2017-10-11 18:56                         ` Linus Torvalds
2017-10-11 19:28                           ` Paul E. McKenney
2017-10-11 19:59                           ` Dmitry Vyukov
2017-10-11 17:14                   ` Paul E. McKenney
2017-10-11 17:19             ` Mark Rutland
2017-10-11 16:50           ` Paul E. McKenney
2017-10-11 16:07       ` David Howells
2017-10-11 16:17         ` Peter Zijlstra
2017-10-11 16:19         ` Paul E. McKenney
2017-10-11 15:28     ` David Howells
2017-10-11 16:02       ` Paul E. McKenney
2017-10-10  9:59 ` David Howells
2017-10-10 15:52   ` Paul E. McKenney
2017-10-11 12:21 ` [PATCH RFC tip/core/rcu 0/15] Remove to-be-unneeded smp_read_barrier_depends() David Howells
2017-10-11 12:56   ` Paul E. McKenney

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20171010084334.nbyhryiwyrl6km4u@hirez.programming.kicks-ass.net \
    --to=peterz@infradead.org \
    --cc=coreteam@netfilter.org \
    --cc=davem@davemloft.net \
    --cc=dhowells@redhat.com \
    --cc=fw@strlen.de \
    --cc=kadlec@blackhole.kfki.hu \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mark.rutland@arm.com \
    --cc=mingo@kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=netfilter-devel@vger.kernel.org \
    --cc=pablo@netfilter.org \
    --cc=paulmck@linux.vnet.ibm.com \
    --cc=torvalds@linux-foundation.org \
    --cc=will.deacon@arm.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).