linux-kernel - Re: [PATCH v3] tools/memory-model: Make ppo a subrelation of po

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: <Y/0HEESX2wDWtPS1@andrea>
Date:   Mon, 27 Feb 2023 20:40:00 +0100
From:   Andrea Parri <parri.andrea@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>,
        Jonas Oberhauser <jonas.oberhauser@...wei.com>,
        will@...nel.org, peterz@...radead.org, boqun.feng@...il.com,
        npiggin@...il.com, dhowells@...hat.com, j.alglave@....ac.uk,
        luc.maranget@...ia.fr, akiyks@...il.com, dlustig@...dia.com,
        joel@...lfernandes.org, urezki@...il.com, quic_neeraju@...cinc.com,
        frederic@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] tools/memory-model: Make ppo a subrelation of po

> The LKMM doesn't believe that a control or data dependency orders a 
> plain write after a marked read.  Hence in this test it thinks that P1's 
> store to u0 can happen before the load of x1.  I don't remember why we 
> did it this way -- probably we just wanted to minimize the restrictions 
> on when plain accesses can execute.  (I do remember the reason for 
> making address dependencies induce order; it was so RCU would work.)
> 
> The patch below will change what the LKMM believes.  It eliminates the 
> positive outcome of the litmus test and the data race.  Should it be 
> adopted into the memory model?

(Unpopular opinion I know,) it should drop dependencies ordering, not
add/promote it.

  Andrea