From: Alan Stern <stern@rowland.harvard.edu>
To: Will Deacon <will@kernel.org>
Cc: "Paul E. McKenney" <paulmck@kernel.org>,
parri.andrea@gmail.com, peterz@infradead.org,
boqun.feng@gmail.com, npiggin@gmail.com, dhowells@redhat.com,
j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com,
dlustig@nvidia.com, joel@joelfernandes.org,
viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org,
linux-arch@vger.kernel.org
Subject: Re: Litmus test for question from Al Viro
Date: Mon, 5 Oct 2020 11:16:39 -0400 [thread overview]
Message-ID: <20201005151639.GE376584@rowland.harvard.edu> (raw)
In-Reply-To: <20201005151313.GA23892@willie-the-truck>
On Mon, Oct 05, 2020 at 04:13:13PM +0100, Will Deacon wrote:
> > The failure to recognize the dependency in P0 should be considered a
> > combined limitation of the memory model and herd7. It's not a simple
> > mistake that can be fixed by a small rewrite of herd7; rather it's a
> > deliberate choice we made based on herd7's inherent design. We
> > explicitly said that control dependencies extend only to the code in the
> > branches of an "if" statement; anything beyond the end of the statement
> > is not considered to be dependent.
>
> Interesting. How does this interact with loops that are conditionally broken
> out of, e.g. a relaxed cmpxchg() loop or an smp_cond_load_relaxed() call
> prior to a WRITE_ONCE()?
Heh -- We finesse this issue by not supporting loops at all! :-)
Alan
next prev parent reply other threads:[~2020-10-05 15:16 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-01 4:51 Litmus test for question from Al Viro Paul E. McKenney
2020-10-01 16:15 ` Alan Stern
2020-10-01 16:36 ` Al Viro
2020-10-01 18:39 ` Alan Stern
2020-10-01 19:29 ` Al Viro
2020-10-01 21:30 ` Paul E. McKenney
2020-10-03 2:01 ` Alan Stern
2020-10-03 13:22 ` Alan Stern
2020-10-03 15:16 ` Akira Yokosawa
2020-10-03 17:13 ` Bug in herd7 [Was: Re: Litmus test for question from Al Viro] Alan Stern
2020-10-03 22:50 ` Akira Yokosawa
2020-10-04 1:40 ` [PATCH] tools: memory-model: Document that the LKMM can easily miss control dependencies Alan Stern
2020-10-04 21:07 ` joel
2020-10-04 23:12 ` Paul E. McKenney
2020-10-05 15:15 ` Bug in herd7 [Was: Re: Litmus test for question from Al Viro] Luc Maranget
2020-10-05 15:53 ` Alan Stern
2020-10-05 16:52 ` Paul E. McKenney
2020-10-05 18:19 ` Alan Stern
2020-10-05 19:18 ` Paul E. McKenney
2020-10-05 19:48 ` Alan Stern
2020-10-06 16:39 ` Paul E. McKenney
2020-10-06 17:05 ` Alan Stern
2020-10-07 17:50 ` Paul E. McKenney
2020-10-07 19:40 ` Alan Stern
2020-10-07 22:38 ` Paul E. McKenney
2020-10-08 2:25 ` Alan Stern
2020-10-08 2:50 ` Paul E. McKenney
2020-10-08 14:01 ` Alan Stern
2020-10-08 18:32 ` Paul E. McKenney
2020-10-05 15:54 ` Paul E. McKenney
2020-10-04 23:31 ` Litmus test for question from Al Viro Paul E. McKenney
2020-10-05 2:38 ` Alan Stern
2020-10-05 8:20 ` Will Deacon
2020-10-05 9:12 ` Will Deacon
2020-10-05 14:01 ` Paul E. McKenney
2020-10-05 14:23 ` Alan Stern
2020-10-05 15:13 ` Will Deacon
2020-10-05 15:16 ` Alan Stern [this message]
2020-10-05 15:35 ` Peter Zijlstra
2020-10-05 15:49 ` Paul E. McKenney
2020-10-05 14:16 ` Alan Stern
2020-10-05 14:03 ` Paul E. McKenney
2020-10-05 14:24 ` Alan Stern
2020-10-05 14:44 ` joel
2020-10-05 15:55 ` Paul E. McKenney
2020-10-05 8:36 ` David Laight
2020-10-05 13:59 ` Paul E. McKenney
2020-10-03 16:08 ` joel
2020-10-03 16:11 ` joel
2020-10-04 23:13 ` Paul E. McKenney
2020-10-03 2:35 ` Jon Masters
2020-10-04 23:32 ` 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=20201005151639.GE376584@rowland.harvard.edu \
--to=stern@rowland.harvard.edu \
--cc=akiyks@gmail.com \
--cc=boqun.feng@gmail.com \
--cc=dhowells@redhat.com \
--cc=dlustig@nvidia.com \
--cc=j.alglave@ucl.ac.uk \
--cc=joel@joelfernandes.org \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luc.maranget@inria.fr \
--cc=npiggin@gmail.com \
--cc=parri.andrea@gmail.com \
--cc=paulmck@kernel.org \
--cc=peterz@infradead.org \
--cc=viro@zeniv.linux.org.uk \
--cc=will@kernel.org \
/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).