From: Peter Zijlstra <peterz@infradead.org>
To: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
Cc: mingo@redhat.com, sasha.levin@oracle.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] tools/liblockdep: add userspace version of READ_ONCE
Date: Thu, 11 Feb 2016 16:16:10 +0100 [thread overview]
Message-ID: <20160211151610.GL6357@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1455147212-2389-2-git-send-email-alfredoalvarezernandez@gmail.com>
On Thu, Feb 11, 2016 at 12:33:30AM +0100, Alfredo Alvarez Fernandez wrote:
> From: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
>
> This was added to the kernel code in 1658d35ead5d ("list: Use
> READ_ONCE() when testing for empty lists")
> There's nothing special we need to do about it in userspace.
>
> Signed-off-by: Alfredo Alvarez Fernandez <alfredoalvarezfernandez@gmail.com>
> ---
> tools/lib/lockdep/uinclude/linux/compiler.h | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/tools/lib/lockdep/uinclude/linux/compiler.h b/tools/lib/lockdep/uinclude/linux/compiler.h
> index 6386dc3..fd3e56a 100644
> --- a/tools/lib/lockdep/uinclude/linux/compiler.h
> +++ b/tools/lib/lockdep/uinclude/linux/compiler.h
> @@ -3,6 +3,7 @@
>
> #define __used __attribute__((__unused__))
> #define unlikely
> +#define READ_ONCE(x) (x)
> #define WRITE_ONCE(x, val) x=(val)
I would argue we'd still very much want the volatile cast for both READ
and WRITE_ONCE().
Why do these things have different semantics between user and kernel
space?
next prev parent reply other threads:[~2016-02-11 15:16 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-10 23:33 [PATCH 0/3] lockdep: liblockdep: Prevent chain_key collisions Alfredo Alvarez Fernandez
2016-02-10 23:33 ` [PATCH 1/3] tools/liblockdep: add userspace version of READ_ONCE Alfredo Alvarez Fernandez
2016-02-11 15:16 ` Peter Zijlstra [this message]
2016-02-16 16:37 ` Sasha Levin
2016-02-10 23:33 ` [PATCH 2/3] tools/liblockdep: add tests Alfredo Alvarez Fernandez
2016-02-10 23:33 ` [PATCH 3/3] lockdep: prevent chain_key collisions Alfredo Alvarez Fernandez
2016-02-17 8:38 ` Ingo Molnar
2016-02-19 6:48 ` [PATCH v2 0/3] lockdep: liblockdep: Prevent " Alfredo Alvarez Fernandez
2016-02-19 6:48 ` [PATCH v2 1/3] tools/liblockdep: add userspace version of READ_ONCE Alfredo Alvarez Fernandez
2016-02-29 11:22 ` [tip:locking/core] tools/lib/lockdep: Add userspace version of READ_ONCE() tip-bot for Alfredo Alvarez Fernandez
2016-02-19 6:48 ` [PATCH v2 2/3] tools/liblockdep: add tests Alfredo Alvarez Fernandez
2016-02-29 11:23 ` [tip:locking/core] tools/lib/lockdep: Add tests for AA and ABBA locking tip-bot for Alfredo Alvarez Fernandez
2016-02-19 6:48 ` [PATCH v2 3/3] lockdep: prevent and detect chain_key collisions Alfredo Alvarez Fernandez
2016-02-29 11:24 ` [tip:locking/core] locking/lockdep: Detect " tip-bot for Ingo Molnar
2016-02-29 11:24 ` [tip:locking/core] locking/lockdep: Prevent " tip-bot for Alfredo Alvarez Fernandez
2016-02-16 16:38 ` [PATCH 0/3] lockdep: liblockdep: " Sasha Levin
2016-02-16 17:22 ` Peter Zijlstra
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