From: ebiederm@xmission.com (Eric W. Biederman)
To: David Howells <dhowells@redhat.com>
Cc: torvalds@osdl.org, akpm@osdl.org, mingo@redhat.com,
alan@redhat.com, linux-arch@vger.kernel.org,
linuxppc64-dev@ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Document Linux's memory barriers [try #4]
Date: Sun, 12 Mar 2006 10:15:20 -0700 [thread overview]
Message-ID: <m1veujy47r.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <16835.1141936162@warthog.cambridge.redhat.com> (David Howells's message of "Thu, 09 Mar 2006 20:29:22 +0000")
A small nit. You are not documenting the most subtle memory barrier:
smp_read_barrier_depends(); Which is a deep requirement of the RCU
code.
As I understand it. On some architectures (alpha) without at least
this a load from a pointer can load from the an old pointer value.
At one point it was suggested this be called:
read_memory_barrier_data_dependent().
Simply calling: rcu_dereference is what all users should call but
the semantics should be documented at least so that people porting
Linux can have a chance of getting it right.
Eric
next prev parent reply other threads:[~2006-03-12 17:17 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20060315200956.4a9e2cb3.akpm@osdl.org>
2006-03-09 20:29 ` [PATCH] Document Linux's memory barriers [try #4] David Howells
2006-03-09 23:34 ` Paul Mackerras
2006-03-09 23:45 ` Michael Buesch
2006-03-09 23:56 ` Linus Torvalds
2006-03-10 0:07 ` Michael Buesch
2006-03-10 0:48 ` Alan Cox
2006-03-10 0:54 ` Paul Mackerras
2006-03-10 15:19 ` David Howells
2006-03-11 0:01 ` Paul Mackerras
2006-03-10 5:28 ` Nick Piggin
2006-03-15 11:10 ` David Howells
2006-03-15 11:51 ` Nick Piggin
2006-03-15 13:47 ` David Howells
2006-03-15 23:21 ` Nick Piggin
2006-03-12 17:15 ` Eric W. Biederman [this message]
2006-03-14 21:26 ` David Howells
2006-03-14 21:48 ` Paul Mackerras
2006-03-14 23:59 ` David Howells
2006-03-15 0:20 ` Linus Torvalds
2006-03-15 1:19 ` David Howells
2006-03-15 1:47 ` Linus Torvalds
2006-03-15 1:25 ` Nick Piggin
2006-03-15 0:54 ` Paul Mackerras
2006-03-15 14:23 ` [PATCH] Document Linux's memory barriers [try #5] David Howells
2006-03-16 23:17 ` Paul E. McKenney
2006-03-16 23:55 ` Linus Torvalds
2006-03-17 1:29 ` Paul E. McKenney
2006-03-17 5:32 ` Linus Torvalds
2006-03-17 6:23 ` Paul E. McKenney
2006-03-23 18:34 ` David Howells
2006-03-23 19:28 ` Linus Torvalds
2006-03-23 22:26 ` Paul E. McKenney
[not found] ` <21253.1142509812@warthog.cambridge.redhat.com>
[not found] ` <Pine.LNX.4.64.0603160914410.3618@g5.osdl.org>
2006-03-17 1:20 ` Nick Piggin
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