Re: [tip:x86/urgent] x86: Add memory modify constraints to xchg() and cmpxchg()

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From: Linus Torvalds
Date: Wednesday, July 28, 2010 - 8:45 am

On Tue, Jul 27, 2010 at 10:33 PM, tip-bot for H. Peter Anvin
<hpa@zytor.com> wrote:

Ack. I assume this doesn't really change the code generated? At least
not with a gcc that honors the whole memory clobber thing properly?

I also suspect that we can/should get rid of the __xg() thing - it was
there just to make sure gcc didn't see the memory read as a single
word and tried to optimize it. With the "+m" it probably doesn't
matter any more (don't know if it ever did)

               Linus
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Messages in current thread:
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Tue Jul 13, 11:21 am)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Tue Jul 13, 4:49 pm)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 10:19 am)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 10:34 am)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 10:57 am)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 11:15 am)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 1:40 pm)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 1:58 pm)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 2:11 pm)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 2:11 pm)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Wed Jul 14, 2:11 pm)
Re: [patch 134/149] x86, paravirt: Add a global synchroniz ..., Jeremy Fitzhardinge, (Tue Jul 27, 10:46 am)
xchg() and cmpxchg(), H. Peter Anvin, (Tue Jul 27, 4:57 pm)
[tip:x86/urgent] x86: Add memory modify constraints to xch ..., tip-bot for H. Peter ..., (Tue Jul 27, 10:33 pm)
Re: [tip:x86/urgent] x86: Add memory modify constraints to ..., Linus Torvalds, (Wed Jul 28, 8:45 am)
[tip:x86/asm] x86, asm: Clean up and simplify &lt;asm/cmpxchg.h&gt;, tip-bot for H. Peter ..., (Wed Jul 28, 4:28 pm)
[tip:x86/asm] x86, asm: Move cmpxchg emulation code to arc ..., tip-bot for H. Peter ..., (Thu Jul 29, 1:12 pm)
[tip:x86/asm] x86, asm: Merge cmpxchg_486_u64() and cmpxch ..., tip-bot for H. Peter ..., (Thu Jul 29, 1:13 pm)
Re: [tip:x86/urgent] x86: Add memory modify constraints to ..., Jeremy Fitzhardinge, (Mon Aug 2, 4:51 pm)
Re: [stable] [tip:x86/urgent] x86: Add memory modify const ..., Tomáš Janoušek, (Thu Sep 9, 12:53 pm)
Re: [stable] [tip:x86/urgent] x86: Add memory modify const ..., Tomáš Janoušek, (Thu Sep 9, 2:09 pm)
Re: [stable] [tip:x86/urgent] x86: Add memory modify const ..., Tomáš Janoušek, (Fri Sep 10, 6:10 am)
Re: [stable] [tip:x86/urgent] x86: Add memory modify const ..., Tomáš Janoušek, (Fri Sep 24, 12:17 am)