Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
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- To: Borislav Petkov <bp@xxxxxxxxx>
- Subject: Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- From: "H. Peter Anvin" <hpa@xxxxxxxxx>
- Date: Wed, 20 Apr 2016 15:29:30 -0700
- Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, Tony Luck <tony.luck@xxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Chris Zankel <chris@xxxxxxxxxx>, Max Filippov <jcmvbkbc@xxxxxxxxx>, x86@xxxxxxxxxx, linux-alpha@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, linux-xtensa@xxxxxxxxxxxxxxxx, linux-arch@xxxxxxxxxxxxxxx, Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
- In-reply-to: <20160420213637.GA4978@pd.tnic>
- List-id: <linux-ia64.vger.kernel.org>
- References: <1460041951-22347-11-git-send-email-mhocko@kernel.org> <20160413090829.GB29579@gmail.com> <20160413091625.GF14351@dhcp22.suse.cz> <20160413091943.GA17858@gmail.com> <20160413102731.GA29896@gmail.com> <20160413124943.GH14351@dhcp22.suse.cz> <20160420134019.GX3448@twins.programming.kicks-ass.net> <91A11395-ACAA-4043-B770-2DF6CBAED54C@zytor.com> <20160420204501.GA6815@pd.tnic> <5717EF59.1030709@zytor.com> <20160420213637.GA4978@pd.tnic>
- User-agent: K-9 Mail for Android
On April 20, 2016 2:36:37 PM PDT, Borislav Petkov <bp@xxxxxxxxx> wrote:
>On Wed, Apr 20, 2016 at 02:06:33PM -0700, H. Peter Anvin wrote:
>> Setting ret to sem doesn't make any sense. Just use "=a" and "a".
>
>Yeah, that's what Michal's patch ontop does.
>
>And to answer my own question: we need the "a" (sem) input for the fast
>path.
>
>I guess we can still move "1" (RWSEM_ACTIVE_WRITE_BIAS) before the
>asm():
>
> long tmp = RWSEM_ACTIVE_WRITE_BIAS;
>
>One thing I'm still not clear on is why we need the output tmp operand:
>"=d" (tmp) ?
Since it is a fixed register we could just mark edx clobbered, but with more flexible register constraints it can permit gcc to allocate a temp resister for us.
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- References:
- [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
- Re: [PATCH 10/11] x86, rwsem: provide __down_write_killable
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