linux-kernel - Re: [PATCH] firmware: wake all waiters

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] [day] [month] [year] [list]

Message-ID: <20170712184519.GV21846@wotan.suse.de>
Date:   Wed, 12 Jul 2017 20:45:19 +0200
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        DanielWagnerwagi@...om.org, Boqun Feng <boqun.feng@...il.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Ming Lei <ming.lei@...hat.com>,
        "Li, Yi" <yi1.li@...ux.intel.com>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        Jakub Kicinski <jakub.kicinski@...ronome.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Petr Mladek <pmladek@...e.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        David Howells <dhowells@...hat.com>,
        Alan Cox <alan@...ux.intel.com>, Theodore Ts'o <tytso@....edu>,
        oss-drivers@...ronome.com
Subject: Re: [PATCH] firmware: wake all waiters

On Wed, Jul 05, 2017 at 09:33:38AM -0700, Linus Torvalds wrote:
> On Wed, Jul 5, 2017 at 9:18 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> > In any case, I'm not seeing why you call it idiotic.
> 
> Have you read the problems?
> 
> There were originally three users:
> 
>  - one of them is firmware loading, and it was actively *buggy* due to
> using hat shit interface, and it's going away

To be fair the issue with the firmware loading was due to a regression on the
port from using swait/completion to swait. swake_up() was used instead of
swake_up_all(). Before the port complate_all() was used instead of just
complete().

So I would personally not add the firmware API to the list of reasons why swait
would be crap.

The more *general* semantics issue you pointed out with swake_up() though seem
more reasonable to be attacking the swait API and those are best followed on
the other thread [0].

I should also point out that there are *other* issues with the firmware API on
this whole wait stuff, but that have been present since even before when we
were using the regular wait / completion API -- a wake was never issued upon an
error in some situations on some kernel builds. I have a fix for that now along
with a test case for it which I'll post soon. After all these fixes the code
works as expected with either the swait API or the good 'ol wait/completion
API. But given swait is still out by you as only specialized I did already post
patches to revert the firmware API to switch back to the wait/completion API.

[0] https://lkml.kernel.org/r/CA+55aFykNULx-b6M6FmUYdK2cn-OJKKfjaPwLN5xZGK+bioGaA@mail.gmail.com

  Luis