From 79e1dd05d1a22e95ab6d54d21836f478b3b56976 Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Wed, 30 Sep 2009 17:07:54 +0200 Subject: x86: Provide an alternative() based cmpxchg64() cmpxchg64() today generates, to quote Linus, "barf bag" code. cmpxchg64() is about to get used in the scheduler to fix a bug there, but it's a prerequisite that cmpxchg64() first be made non-sucking. This patch turns cmpxchg64() into an efficient implementation that uses the alternative() mechanism to just use the raw instruction on all modern systems. Note: the fallback is NOT smp safe, just like the current fallback is not SMP safe. (Interested parties with i486 based SMP systems are welcome to submit fix patches for that.) Signed-off-by: Arjan van de Ven Acked-by: Linus Torvalds [ fixed asm constraint bug ] Fixed-by: Eric Dumazet Cc: Martin Schwidefsky Cc: John Stultz Cc: Peter Zijlstra LKML-Reference: <20090930170754.0886ff2e@infradead.org> Signed-off-by: Ingo Molnar --- arch/x86/lib/Makefile | 2 +- arch/x86/lib/cmpxchg8b_emu.S | 57 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+), 1 deletion(-) create mode 100644 arch/x86/lib/cmpxchg8b_emu.S (limited to 'arch/x86/lib') diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index 9e609206fac9..3e549b8ec8c9 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -15,7 +15,7 @@ ifeq ($(CONFIG_X86_32),y) obj-y += atomic64_32.o lib-y += checksum_32.o lib-y += strstr_32.o - lib-y += semaphore_32.o string_32.o + lib-y += semaphore_32.o string_32.o cmpxchg8b_emu.o lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o else diff --git a/arch/x86/lib/cmpxchg8b_emu.S b/arch/x86/lib/cmpxchg8b_emu.S new file mode 100644 index 000000000000..828cb710dec2 --- /dev/null +++ b/arch/x86/lib/cmpxchg8b_emu.S @@ -0,0 +1,57 @@ +/* + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; version 2 + * of the License. + * + */ + +#include +#include +#include +#include + + +.text + +/* + * Inputs: + * %esi : memory location to compare + * %eax : low 32 bits of old value + * %edx : high 32 bits of old value + * %ebx : low 32 bits of new value + * %ecx : high 32 bits of new value + */ +ENTRY(cmpxchg8b_emu) +CFI_STARTPROC + +# +# Emulate 'cmpxchg8b (%esi)' on UP except we don't +# set the whole ZF thing (caller will just compare +# eax:edx with the expected value) +# +cmpxchg8b_emu: + pushfl + cli + + cmpl (%esi), %eax + jne not_same + cmpl 4(%esi), %edx + jne half_same + + movl %ebx, (%esi) + movl %ecx, 4(%esi) + + popfl + ret + + not_same: + movl (%esi), %eax + half_same: + movl 4(%esi), %edx + + popfl + ret + +CFI_ENDPROC +ENDPROC(cmpxchg8b_emu) -- cgit v1.2.2 From 04edbdef02ec4386a2ae38cab7ae7d166e17a756 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 1 Oct 2009 07:30:38 +0200 Subject: x86: Don't generate cmpxchg8b_emu if CONFIG_X86_CMPXCHG64=y Conditionaly compile cmpxchg8b_emu.o and EXPORT_SYMBOL(cmpxchg8b_emu). This reduces the kernel size a bit. Signed-off-by: Eric Dumazet Cc: Arjan van de Ven Cc: Martin Schwidefsky Cc: John Stultz Cc: Peter Zijlstra Cc: Linus Torvalds LKML-Reference: <4AC43E7E.1000600@gmail.com> Signed-off-by: Ingo Molnar --- arch/x86/lib/Makefile | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'arch/x86/lib') diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile index 3e549b8ec8c9..85f5db95c60f 100644 --- a/arch/x86/lib/Makefile +++ b/arch/x86/lib/Makefile @@ -15,8 +15,10 @@ ifeq ($(CONFIG_X86_32),y) obj-y += atomic64_32.o lib-y += checksum_32.o lib-y += strstr_32.o - lib-y += semaphore_32.o string_32.o cmpxchg8b_emu.o - + lib-y += semaphore_32.o string_32.o +ifneq ($(CONFIG_X86_CMPXCHG64),y) + lib-y += cmpxchg8b_emu.o +endif lib-$(CONFIG_X86_USE_3DNOW) += mmx_32.o else obj-y += io_64.o iomap_copy_64.o -- cgit v1.2.2