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Christoph Lameter
authored and
Tejun Heo
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Feb 28, 2011
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refs/heads/master: 7c3343392172ba98d9d90a83edcc4c2e80897009 | ||
refs/heads/master: b9ec40af0e18fb7d02106be148036c2ea490fdf9 |
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/* | ||
* 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 <linux/linkage.h> | ||
#include <asm/alternative-asm.h> | ||
#include <asm/frame.h> | ||
#include <asm/dwarf2.h> | ||
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.text | ||
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/* | ||
* Inputs: | ||
* %rsi : memory location to compare | ||
* %rax : low 64 bits of old value | ||
* %rdx : high 64 bits of old value | ||
* %rbx : low 64 bits of new value | ||
* %rcx : high 64 bits of new value | ||
* %al : Operation successful | ||
*/ | ||
ENTRY(this_cpu_cmpxchg16b_emu) | ||
CFI_STARTPROC | ||
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# | ||
# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not | ||
# via the ZF. Caller will access %al to get result. | ||
# | ||
# Note that this is only useful for a cpuops operation. Meaning that we | ||
# do *not* have a fully atomic operation but just an operation that is | ||
# *atomic* on a single cpu (as provided by the this_cpu_xx class of | ||
# macros). | ||
# | ||
this_cpu_cmpxchg16b_emu: | ||
pushf | ||
cli | ||
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cmpq %gs:(%rsi), %rax | ||
jne not_same | ||
cmpq %gs:8(%rsi), %rdx | ||
jne not_same | ||
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movq %rbx, %gs:(%rsi) | ||
movq %rcx, %gs:8(%rsi) | ||
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popf | ||
mov $1, %al | ||
ret | ||
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not_same: | ||
popf | ||
xor %al,%al | ||
ret | ||
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CFI_ENDPROC | ||
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ENDPROC(this_cpu_cmpxchg16b_emu) |