Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable

From	Michal Hocko <mhocko@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
Date	2016-04-20 23:00 +0200
Message-ID	<rq7o6-5F5-5@gated-at.bofh.it> (permalink)
References	(5 earlier) <rnqdA-8e7-25@gated-at.bofh.it> <rnsyK-1lV-15@gated-at.bofh.it> <rq0FY-fr-19@gated-at.bofh.it> <rq4JC-3Ai-49@gated-at.bofh.it> <rq7eq-5Ab-9@gated-at.bofh.it>
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On Wed 20-04-16 22:45:01, Borislav Petkov wrote:
> On Wed, Apr 20, 2016 at 11:04:05AM -0700, H. Peter Anvin wrote:
> > The reason it breaks is because the same register can't be an
> > input-output register and a separate input. However, the input side of
> > the input-output is probably undefined, and so gcc may not notice.
> 
> So Michal and I talked about this a while ago. Why do we need the '"a"
> (sem)' input dependency if '"+a" (ret)' already supplies the same thing?
> 
> There's also that "=d" (tmp) thing which we don't really need as an
> output, right?
> 
> I.e., can we simplify like this?

I am for any simplification, my gcc-asm-foo is just too weak and I
wanted my change to be as minimal as possible. So if you feel you can
clean up this I would more than welcome that. Maybe a follow up patch
would be a better approach so that we can check that the generated code
hasn't changed.

Thanks!
-- 
Michal Hocko
SUSE Labs

Thread

Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Peter Zijlstra <peterz@infradead.org> - 2016-04-20 15:50 +0200
  Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable "H. Peter Anvin" <hpa@zytor.com> - 2016-04-20 20:10 +0200
    Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-20 22:50 +0200
      Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Michal Hocko <mhocko@kernel.org> - 2016-04-20 23:00 +0200
      Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable "H. Peter Anvin" <hpa@zytor.com> - 2016-04-20 23:10 +0200
        Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-20 23:40 +0200
          Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable "H. Peter Anvin" <hpa@zytor.com> - 2016-04-21 00:40 +0200
            Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-21 13:40 +0200
              Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Michal Hocko <mhocko@kernel.org> - 2016-04-21 15:10 +0200
                Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Borislav Petkov <bp@alien8.de> - 2016-04-21 15:30 +0200
            [PATCH] x86/locking/rwsem: Cleanup ____down_write() Borislav Petkov <bp@alien8.de> - 2016-04-27 14:10 +0200
              [tip:locking/rwsem] locking/rwsem, x86: Clean up ____down_write() tip-bot for Borislav Petkov <tipbot@zytor.com> - 2016-04-28 12:30 +0200
  Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable Ingo Molnar <mingo@kernel.org> - 2016-04-22 09:00 +0200

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