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Message-ID: <CAG48ez2WJo5+wqWi1nxstR=WWyseVfZPMnpdDBsZKW5G+Tt3KQ@mail.gmail.com>
Date: Tue, 24 Mar 2020 17:56:15 +0100
From: Jann Horn <jannh@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will@...nel.org>, kernel list <linux-kernel@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>, Kees Cook <keescook@...omium.org>,
Maddie Stone <maddiestone@...gle.com>, Marco Elver <elver@...gle.com>,
"Paul E . McKenney" <paulmck@...nel.org>, Thomas Gleixner <tglx@...utronix.de>,
kernel-team <kernel-team@...roid.com>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>, Oleg Nesterov <oleg@...hat.com>
Subject: Re: [RFC PATCH 03/21] list: Annotate lockless list primitives with data_race()
On Tue, Mar 24, 2020 at 5:51 PM Peter Zijlstra <peterz@...radead.org> wrote:
> On Tue, Mar 24, 2020 at 03:36:25PM +0000, Will Deacon wrote:
> > diff --git a/include/linux/list.h b/include/linux/list.h
> > index 4fed5a0f9b77..4d9f5f9ed1a8 100644
> > --- a/include/linux/list.h
> > +++ b/include/linux/list.h
> > @@ -279,7 +279,7 @@ static inline int list_is_last(const struct list_head *list,
> > */
> > static inline int list_empty(const struct list_head *head)
> > {
> > - return READ_ONCE(head->next) == head;
> > + return data_race(READ_ONCE(head->next) == head);
> > }
>
> list_empty() isn't lockless safe, that's what we have
> list_empty_careful() for.
That thing looks like it could also use some READ_ONCE() sprinkled in...
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