linux-kernel - Re: LKMM: Making RMW barriers explicit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <adc97697-9a71-4ec8-a9fa-1558a7a1d181@rowland.harvard.edu>
Date: Thu, 23 May 2024 12:05:52 -0400
From: Alan Stern <stern@...land.harvard.edu>
To: Hernan Ponce de Leon <hernan.poncedeleon@...weicloud.com>
Cc: Jonas Oberhauser <jonas.oberhauser@...weicloud.com>,
  "Paul E. McKenney" <paulmck@...nel.org>, linux-kernel@...r.kernel.org,
  linux-arch@...r.kernel.org, kernel-team@...a.com, parri.andrea@...il.com,
  boqun.feng@...il.com, j.alglave@....ac.uk, luc.maranget@...ia.fr,
  Joel Fernandes <joel@...lfernandes.org>
Subject: Re: LKMM: Making RMW barriers explicit

On Thu, May 23, 2024 at 04:26:23PM +0200, Hernan Ponce de Leon wrote:
> On 5/23/2024 4:05 PM, Alan Stern wrote:
> > Overall, it seems better to have herd7 assign the right tag, but change
> > the way the .def file works so that it can tell herd7 which tag to use
> > in each of the success and failure cases.
> 
> I am not fully sure how herd7 uses the .def file, but I guess something like
> adding a second memory tag to __cmpxchg could work
> 
> cmpxchg(X,V,W) __cmpxchg{mb, once}(X,V,W)
> cmpxchg_relaxed(X,V,W) __cmpxchg{once, once}(X,V,W)
> cmpxchg_acquire(X,V,W) __cmpxchg{acquire, acquire}(X,V,W)
> cmpxchg_release(X,V,W) __cmpxchg{release, release}(X,V,W)

Right, except that the last two should be:

cmpxchg_acquire(X,V,W) __cmpxchg{acquire, once}(X,V,W)
cmpxchg_release(X,V,W) __cmpxchg{release, once}(X,V,W)

Alan