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Subj : Re: YALFAm (Yet Another Lock Free Approach, maybe)
To   : comp.programming.threads
From : Chris Thomasson
Date : Tue May 17 2005 04:12 am

>> it can use the "more" lightweight mfence instruction...
>>
> Instructions.  You need an additional membar for the release semantics if 
> you
> are storing into a non null hazard pointer.

So, for x86 SMR implmentation:


..align 16
..globl ac_i686_lfgc_smr_activate
ac_i686_lfgc_smr_activate:
  movl 4(%esp), %edx
  movl 8(%esp), %ecx


; you would need to add an extra mfence right here

  ; mfence

; before the compare loop?


ac_i686_lfgc_smr_activate_reload:
  movl (%ecx), %eax
  movl %eax, (%edx)
  mfence
  cmpl (%ecx), %eax
  jne ac_i686_lfgc_smr_activate_reload
ret


Humm, this changes things...

.

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