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percpu: Omit segment prefix in the UP case for cmpxchg_double 

Omit the segment prefix in the UP case. GS is not used then
and we will generate segfaults if cmpxchg16b is used otherwise.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Lameter 2011-03-26 20:57:18 -05:00 committed by Linus Torvalds
parent 76597cd314
commit d7c3f8cee8
2 changed files with 16 additions and 8 deletions
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10
arch/x86/include/asm/percpu.h
View File

@ -45,7 +45,7 @@
#include <linux/stringify.h>
#ifdef CONFIG_SMP
#define __percpu_arg(x) "%%"__stringify(__percpu_seg)":%P" #x
#define __percpu_prefix "%%"__stringify(__percpu_seg)":"
#define __my_cpu_offset percpu_read(this_cpu_off)
/*
@ -62,9 +62,11 @@
(typeof(*(ptr)) __kernel __force *)tcp_ptr__; \
})
#else
#define __percpu_arg(x) "%P" #x
#define __percpu_prefix ""
#endif
#define __percpu_arg(x) __percpu_prefix "%P" #x
/*
* Initialized pointers to per-cpu variables needed for the boot
* processor need to use these macros to get the proper address
@ -516,11 +518,11 @@ do { \
typeof(o2) __n2 = n2; \
typeof(o2) __dummy; \
alternative_io("call this_cpu_cmpxchg16b_emu\n\t" P6_NOP4, \
"cmpxchg16b %%gs:(%%rsi)\n\tsetz %0\n\t", \
"cmpxchg16b " __percpu_prefix "(%%rsi)\n\tsetz %0\n\t", \
X86_FEATURE_CX16, \
ASM_OUTPUT2("=a"(__ret), "=d"(__dummy)), \
"S" (&pcp1), "b"(__n1), "c"(__n2), \
"a"(__o1), "d"(__o2)); \
"a"(__o1), "d"(__o2) : "memory"); \
__ret; \
})

14
arch/x86/lib/cmpxchg16b_emu.S
View File

@ -10,6 +10,12 @@
#include <asm/frame.h>
#include <asm/dwarf2.h>
#ifdef CONFIG_SMP
#define SEG_PREFIX %gs:
#else
#define SEG_PREFIX
#endif
.text
/*
@ -37,13 +43,13 @@ this_cpu_cmpxchg16b_emu:
pushf
cli
cmpq %gs:(%rsi), %rax
cmpq SEG_PREFIX(%rsi), %rax
jne not_same
cmpq %gs:8(%rsi), %rdx
cmpq SEG_PREFIX 8(%rsi), %rdx
jne not_same
movq %rbx, %gs:(%rsi)
movq %rcx, %gs:8(%rsi)
movq %rbx, SEG_PREFIX(%rsi)
movq %rcx, SEG_PREFIX 8(%rsi)
popf
mov $1, %al