From: "Paul E. McKenney" <paulmck@kernel.org>
To: Will Deacon <will@kernel.org>
Cc: linux-kernel@vger.kernel.org, Eric Dumazet <edumazet@google.com>,
Jann Horn <jannh@google.com>, Kees Cook <keescook@chromium.org>,
Maddie Stone <maddiestone@google.com>,
Marco Elver <elver@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
kernel-team@android.com, kernel-hardening@lists.openwall.com
Subject: Re: [RFC PATCH 08/21] Revert "list: Use WRITE_ONCE() when initializing list_head structures"
Date: Tue, 31 Mar 2020 06:47:25 -0700 [thread overview]
Message-ID: <20200331134725.GL19865@paulmck-ThinkPad-P72> (raw)
In-Reply-To: <20200331131153.GB30975@willie-the-truck>
On Tue, Mar 31, 2020 at 02:11:54PM +0100, Will Deacon wrote:
> On Mon, Mar 30, 2020 at 04:25:05PM -0700, Paul E. McKenney wrote:
> > On Tue, Mar 24, 2020 at 03:36:30PM +0000, Will Deacon wrote:
> > > This reverts commit 2f073848c3cc8aff2655ab7c46d8c0de90cf4e50.
> > >
> > > There is no need to use WRITE_ONCE() to initialise a non-RCU 'list_head'.
> > >
> > > Cc: Paul E. McKenney <paulmck@kernel.org>
> > > Cc: Peter Zijlstra <peterz@infradead.org>
> > > Signed-off-by: Will Deacon <will@kernel.org>
> >
> > And attention to lockless uses of list_empty() here, correct?
> >
> > Depending on the outcome of discussions on 3/21, I should have added in
> > all three cases.
>
> Yes, patch 3 is where this will get sorted. It looks like we'll have to
> disable KCSAN around the READ_ONCE() over there, but I also need to finish
> wrapping my head around list_empty_careful() because I'm deeply suspicious!
At the very least, it does have the disadvantage of touching an additional
cache line, and up to two additional cache lines in the non-empty case. :-(
Thanx, Paul
next prev parent reply other threads:[~2020-03-31 13:47 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-24 15:36 [RFC PATCH 00/21] Improve list integrity checking Will Deacon
2020-03-24 15:36 ` [RFC PATCH 01/21] list: Remove hlist_unhashed_lockless() Will Deacon
2020-03-24 16:27 ` Greg KH
2020-03-30 23:05 ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 02/21] list: Remove hlist_nulls_unhashed_lockless() Will Deacon
2020-03-24 16:27 ` Greg KH
2020-03-30 23:07 ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 03/21] list: Annotate lockless list primitives with data_race() Will Deacon
2020-03-24 16:20 ` Jann Horn
2020-03-24 16:26 ` Greg KH
2020-03-24 16:38 ` Jann Horn
2020-03-24 16:59 ` Greg KH
2020-03-24 18:22 ` Jann Horn
2020-03-24 16:23 ` Marco Elver
2020-03-24 21:33 ` Will Deacon
2020-03-31 13:10 ` Will Deacon
2020-04-01 6:34 ` Marco Elver
2020-04-01 8:40 ` Will Deacon
2020-03-24 16:51 ` Peter Zijlstra
2020-03-24 16:56 ` Jann Horn
2020-03-24 21:32 ` Will Deacon
2020-03-30 23:13 ` Paul E. McKenney
2020-04-24 17:39 ` Will Deacon
2020-04-27 19:24 ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 04/21] timers: Use hlist_unhashed() instead of open-coding in timer_pending() Will Deacon
2020-03-24 16:30 ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 05/21] list: Comment missing WRITE_ONCE() in __list_del() Will Deacon
2020-03-30 23:14 ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 06/21] list: Remove superfluous WRITE_ONCE() from hlist_nulls implementation Will Deacon
2020-03-30 23:21 ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 07/21] Revert "list: Use WRITE_ONCE() when adding to lists and hlists" Will Deacon
2020-03-30 23:19 ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 08/21] Revert "list: Use WRITE_ONCE() when initializing list_head structures" Will Deacon
2020-03-30 23:25 ` Paul E. McKenney
2020-03-31 13:11 ` Will Deacon
2020-03-31 13:47 ` Paul E. McKenney [this message]
2020-03-24 15:36 ` [RFC PATCH 09/21] list: Remove unnecessary WRITE_ONCE() from hlist_bl_add_before() Will Deacon
2020-03-30 23:30 ` Paul E. McKenney
2020-03-31 12:37 ` Will Deacon
2020-03-24 15:36 ` [RFC PATCH 10/21] kernel-hacking: Make DEBUG_{LIST,PLIST,SG,NOTIFIERS} non-debug options Will Deacon
2020-03-24 16:42 ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 11/21] list: Add integrity checking to hlist implementation Will Deacon
2020-03-24 15:36 ` [RFC PATCH 12/21] list: Poison ->next pointer for non-RCU deletion of 'hlist_nulls_node' Will Deacon
2020-03-30 23:32 ` Paul E. McKenney
2020-03-24 15:36 ` [RFC PATCH 13/21] list: Add integrity checking to hlist_nulls implementation Will Deacon
2020-03-24 15:36 ` [RFC PATCH 14/21] plist: Use CHECK_DATA_CORRUPTION instead of explicit {BUG,WARN}_ON() Will Deacon
2020-03-24 16:42 ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 15/21] list_bl: Use CHECK_DATA_CORRUPTION instead of custom BUG_ON() wrapper Will Deacon
2020-03-24 15:36 ` [RFC PATCH 16/21] list_bl: Extend integrity checking in deletion routines Will Deacon
2020-03-24 15:36 ` [RFC PATCH 17/21] linux/bit_spinlock.h: Include linux/processor.h Will Deacon
2020-03-24 16:28 ` Greg KH
2020-03-24 21:08 ` Will Deacon
2020-03-24 15:36 ` [RFC PATCH 18/21] list_bl: Move integrity checking out of line Will Deacon
2020-03-24 15:36 ` [RFC PATCH 19/21] list_bl: Extend integrity checking to cover the same cases as 'hlist' Will Deacon
2020-03-24 15:36 ` [RFC PATCH 20/21] list: Format CHECK_DATA_CORRUPTION error messages consistently Will Deacon
2020-03-24 16:40 ` Greg KH
2020-03-24 15:36 ` [RFC PATCH 21/21] lkdtm: Extend list corruption checks Will Deacon
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