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* x86, asm: Clean up and simplify <asm/cmpxchg.h>H. Peter Anvin2010-07-281-19/+42
| | | | | | | | | | | | Remove the __xg() hack to create a memory barrier near xchg and cmpxchg; it has been there since 1.3.11 but should not be necessary with "asm volatile" and a "memory" clobber, neither of which were there in the original implementation. However, we *should* make this a volatile reference. Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> LKML-Reference: <AANLkTikAmaDPji-TVDarmG1yD=fwbffcsmEU=YEuP+8r@mail.gmail.com>
* x86, asm: Clean up and simplify set_64bit()H. Peter Anvin2010-07-271-3/+1
| | | | | | | | | | | | | | | | | Clean up and simplify set_64bit(). This code is quite old (1.3.11) and contains a fair bit of auxilliary machinery that current versions of gcc handle just fine automatically. Worse, the auxilliary machinery can actually cause an unnecessary spill to memory. Furthermore, the loading of the old value inside the loop in the 32-bit case is unnecessary: if the value doesn't match, the CMPXCHG8B instruction will already have loaded the "new previous" value for us. Clean up the comment, too, and remove page references to obsolete versions of the Intel SDM. Signed-off-by: H. Peter Anvin <hpa@zytor.com> LKML-Reference: <tip-*@vger.kernel.org>
* x86: Add memory modify constraints to xchg() and cmpxchg()H. Peter Anvin2010-07-271-20/+20
| | | | | | | | | | | | | | | | | | xchg() and cmpxchg() modify their memory operands, not merely read them. For some versions of gcc the "memory" clobber has apparently dealt with the situation, but not for all. Originally-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: H. Peter Anvin <hpa@zytor.com> Cc: Glauber Costa <glommer@redhat.com> Cc: Avi Kivity <avi@redhat.com> Cc: Peter Palfrader <peter@palfrader.org> Cc: Greg KH <gregkh@suse.de> Cc: Alan Cox <alan@lxorguk.ukuu.org.uk> Cc: Zachary Amsden <zamsden@redhat.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Cc: <stable@kernel.org> LKML-Reference: <4C4F7277.8050306@zytor.com>
* x86: Generate cmpxchg build failuresPeter Zijlstra2009-10-091-143/+91
| | | | | | | | | | Rework the x86 cmpxchg() implementation to generate build failures when used on improper types. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> LKML-Reference: <1254771187.21044.22.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
* x86: Fix ASM_X86__ header guardsH. Peter Anvin2008-10-221-3/+3
| | | | | | | | | Change header guards named "ASM_X86__*" to "_ASM_X86_*" since: a. the double underscore is ugly and pointless. b. no leading underscore violates namespace constraints. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
* x86, um: ... and asm-x86 moveAl Viro2008-10-221-0/+185
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: H. Peter Anvin <hpa@zytor.com>
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