Groups > comp.programming.threads > #251

Re: Implicit memory barriers on x86

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From	Edek <edek.pienkowski@gmail.com>
Newsgroups	comp.programming.threads
Subject	Re: Implicit memory barriers on x86
Date	Wed, 08 Jun 2011 23:41:53 +0200
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Assuming you need this

Thr 1

lock_by_xchg
read mem1

Thr2
write ->mem1
write -> spinlock

Isn't that already ordered? For thr2, writes are seen in consistent 
order, for Thr 1 there is total ordering anyway.

Otherwise, see 8.2.3.5. Isn't this affecting

> push eax  #1 store
> pop   eax  #2 load

>> >
>>> > > Seems like based on the above rules:
>>> > > 1) #1 and #2 - no reorder per (D)
>
>> D) Reads may be reordered with older writes to different locations but
>> > > not with older writes to the same location.
>>


Here, #2 will happen before #1, though it gets #1's value.

Edek

PS. Sorry for my previous remark, I never do threads targeting a
CPU family. These guarantees are not general threading guarantees,
and 8.2.5 near the end. I guess you're can retarget whatever
you're writing, when a new CPU is available.

Thread

Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-07 13:47 -0700
  Re: Implicit memory barriers on x86 David Schwartz <davids@webmaster.com> - 2011-06-08 10:11 -0700
    Re: Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-08 12:53 -0700
  Re: Implicit memory barriers on x86 Edek <edek.pienkowski@gmail.com> - 2011-06-08 20:29 +0200
    Re: Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-08 12:48 -0700
      Re: Implicit memory barriers on x86 Edek <edek.pienkowski@gmail.com> - 2011-06-08 23:41 +0200
        Re: Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-08 22:19 -0700
        Re: Implicit memory barriers on x86 David Schwartz <davids@webmaster.com> - 2011-06-09 16:25 -0700
  Re: Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-10 14:19 -0700
    Re: Implicit memory barriers on x86 David Schwartz <davids@webmaster.com> - 2011-06-11 02:57 -0700
      Re: Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-11 09:21 -0700
        Re: Implicit memory barriers on x86 Edek <edek.pienkowski@gmail.com> - 2011-06-11 22:26 +0200
    Re: Implicit memory barriers on x86 Alexander Terekhov <terekhov@web.de> - 2011-06-11 12:31 +0200
      Re: Implicit memory barriers on x86 "Chris M. Thomasson" <cristom@charter.net> - 2011-06-13 09:51 -0700
    Re: Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-11 12:30 -0700
      Re: Implicit memory barriers on x86 Edek <edek.pienkowski@gmail.com> - 2011-06-11 22:18 +0200
        Re: Implicit memory barriers on x86 Rani Sharoni <ranisharoni75@gmail.com> - 2011-06-11 13:31 -0700

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