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Re: Volatile keyword

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On Monday, December 12, 2011 4:51:41 AM UTC-8, rap...@gmail.com wrote:
> Does this make all read/writes happen in full.
> 
> For example, if one thread had
> 
> volatile long a = 0xFFFFFFFF00000000L;
> 
> <do stuff>
> 
> a = ~a;
> 
> If another thread read a, would it always give 0xFFFFFFFF00000000 or
> 0x00000000FFFFFFFF and not partial writes (say it updates 32 bits and
> then the next 32 bits).
> 
> I understand that if two threads do a++, it might only increment
> twice, if they both read the old value at the same time.
> 
> Effectively, does the CPU lock the entire 64-bits for the long when
> doing the write update, and so other threads either seen the updated
> value or the old value?

http://java.sun.com/docs/books/jls/third_edition/html/memory.html#17.4
http://java.sun.com/docs/books/jls/third_edition/html/memory.html#17.7
http://java.sun.com/docs/books/jls/third_edition/html/classes.html#8.3.1.4

-- 
Lew

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Volatile keyword "raphfrk@gmail.com" <raphfrk@gmail.com> - 2011-12-12 04:51 -0800
  Re: Volatile keyword Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-12-12 14:31 +0000
    Re: Volatile keyword "raphfrk@gmail.com" <raphfrk@gmail.com> - 2011-12-12 06:52 -0800
  Re: Volatile keyword Lew <lewbloch@gmail.com> - 2011-12-12 06:34 -0800
  Re: Volatile keyword markspace <-@.> - 2011-12-12 10:00 -0800
    Re: Volatile keyword Tom Anderson <twic@urchin.earth.li> - 2011-12-12 18:41 +0000
      Re: Volatile keyword Patricia Shanahan <pats@acm.org> - 2011-12-12 11:43 -0800
    Re: Volatile keyword Roedy Green <see_website@mindprod.com.invalid> - 2011-12-12 11:15 -0800
      Re: Volatile keyword Robert Klemme <shortcutter@googlemail.com> - 2011-12-13 08:37 +0100
        Re: Volatile keyword Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-12-12 23:54 -0800
          Re: Volatile keyword Robert Klemme <shortcutter@googlemail.com> - 2011-12-14 19:39 +0100
            Re: Volatile keyword Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2011-12-14 10:59 -0800
            Re: Volatile keyword Patricia Shanahan <pats@acm.org> - 2011-12-14 11:00 -0800
              Re: Volatile keyword Robert Klemme <shortcutter@googlemail.com> - 2011-12-14 22:35 +0100
  Re: Volatile keyword Roedy Green <see_website@mindprod.com.invalid> - 2011-12-12 10:55 -0800

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