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79e1dd05d1
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 <arjan@linux.intel.com> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> [ fixed asm constraint bug ] Fixed-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: John Stultz <johnstul@us.ibm.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20090930170754.0886ff2e@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
57 lines
972 B
ArmAsm
57 lines
972 B
ArmAsm
/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*
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*/
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#include <linux/linkage.h>
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#include <asm/alternative-asm.h>
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#include <asm/frame.h>
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#include <asm/dwarf2.h>
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.text
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/*
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* Inputs:
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* %esi : memory location to compare
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* %eax : low 32 bits of old value
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* %edx : high 32 bits of old value
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* %ebx : low 32 bits of new value
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* %ecx : high 32 bits of new value
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*/
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ENTRY(cmpxchg8b_emu)
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CFI_STARTPROC
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#
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# Emulate 'cmpxchg8b (%esi)' on UP except we don't
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# set the whole ZF thing (caller will just compare
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# eax:edx with the expected value)
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#
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cmpxchg8b_emu:
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pushfl
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cli
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cmpl (%esi), %eax
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jne not_same
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cmpl 4(%esi), %edx
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jne half_same
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movl %ebx, (%esi)
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movl %ecx, 4(%esi)
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popfl
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ret
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not_same:
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movl (%esi), %eax
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half_same:
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movl 4(%esi), %edx
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popfl
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ret
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CFI_ENDPROC
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ENDPROC(cmpxchg8b_emu)
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