Messages in this thread Patch in this message |  | | | From | Paolo 'Blaisorblade' Giarrusso <> | | Subject | [PATCH 6/6] x86_64: enable xchg optimization for x86_64 | | Date | Wed, 26 Oct 2005 00:13:52 +0200 |
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From: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
i386 enables the xchg based implementation of r/w semaphores for any processor as good as 486. So it was quite interesting to see x86_64 never using it! And it was even more interesting to see, in rwsem.h:
/* rwsem.h: R/W semaphores implemented using XADD/CMPXCHG for x86_64+ * * Written by David Howells (dhowells@redhat.com). * Ported by Andi Kleen <ak@suse.de> to x86-64. I.e. the implementation was written, is present in the tree, but due to this:
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK #include <linux/rwsem-spinlock.h> /* use a generic implementation */ #else #include <asm/rwsem.h> /* use an arch-specific implementation */ #endif it was probably _NEVER_ compiled!!!
So, handle with care this one-liner, and test it properly.
CC: Andi Kleen <ak@suse.de> Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it> --- arch/x86_64/Kconfig | 5 ++--- 1 files changed, 2 insertions(+), 3 deletions(-) diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig --- a/arch/x86_64/Kconfig +++ b/arch/x86_64/Kconfig @@ -39,11 +39,10 @@ config SBUS bool config RWSEM_GENERIC_SPINLOCK - bool - default y + def_bool n config RWSEM_XCHGADD_ALGORITHM - bool + def_bool y config GENERIC_CALIBRATE_DELAY bool - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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