Messages in this thread Patch in this message | | | Date | Wed, 30 Sep 2009 17:57:27 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [GIT PULL] scheduler fixes |
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On Wed, 30 Sep 2009, Linus Torvalds wrote: > > Pulled. I'd also like to see something that actually fails gracefully on > cmpxchg() of an unsupported size, though. The silent failure still annoys > me.
Oh, and we probably should try to avoid the 'alternates()' code when we can statically determine that cmpxchg8b is fine. We already have that CONFIG_x86_CMPXCHG64 (enabled by PAE support), and we could easily also enable it for some of the CPU cases.
[ If I recall correctly, cmpxchg8b support detection was something that was totally messed up in WNT, and I have this memory of TMTA _not_ claiming to support CX8 in the cpuid bits, but happily supporting the instruction itself - because otherwise WNT would blue-screen on boot or something silly like that.
As a result, the patch below only adds CMPXCHG8B for the obvious Intel CPU's, not for others. There was something really messy about cmpxchg8b and clone CPU's, but I'm not 100% sure about the details, so take this patch with a pinch of salt, and some thinking ]
If we avoid that asm-alternative thing when we can assume the instruction exists, we'll generate less support crud, and we'll avoid the whole issue with that extra 'nop' for padding instruction sizes etc.
Linus
--- arch/x86/Kconfig.cpu | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/arch/x86/Kconfig.cpu b/arch/x86/Kconfig.cpu index 527519b..f2824fb 100644 --- a/arch/x86/Kconfig.cpu +++ b/arch/x86/Kconfig.cpu @@ -400,7 +400,7 @@ config X86_TSC config X86_CMPXCHG64 def_bool y - depends on X86_PAE || X86_64 + depends on X86_PAE || X86_64 || MCORE2 || MPENTIUM4 || MPENTIUMM || MPENTIUMIII || MPENTIUMII || M686 || MATOM # this should be set for all -march=.. options where the compiler # generates cmov. @@ -412,6 +412,7 @@ config X86_MINIMUM_CPU_FAMILY int default "64" if X86_64 default "6" if X86_32 && X86_P6_NOP + default "5" if X86_32 && X86_CMPXCHG64 default "4" if X86_32 && (X86_XADD || X86_CMPXCHG || X86_BSWAP || X86_WP_WORKS_OK) default "3"
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