Groups > comp.lang.java.programmer > #22735

Re: synchronized methods "under the hood"

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From	Roedy Green <see_website@mindprod.com.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: synchronized methods "under the hood"
Organization	Canadian Mind Products
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On Tue, 05 Mar 2013 23:44:34 +0100, Sven Köhler
<remove-sven.koehler@gmail.com> wrote, quoted or indirectly quoted
someone who said :

>Such test and set methods are implemented in Java's Atomic* classes
>(e.g. AtomicInteger). However, you need more than that to implement a
>proper mutex. What I would call a proper mutex puts a thread to sleep,
>if it cannot lock the mutex. To do that, you need to tell the kernel
>that the thread is suspended

I thought he was asking about what happens at the hardware level.
Thread context switching I think is still done with software.

Back in the 1990s I wrote a package in C to allow threads that ran on
a single CPU. Threads had to be well behaved and call "have a
conscience" periodically. It was remarkably simple, just save and
restore contexts.  It is quite bit more complicated when you can
interrupt threads in mid instruction or when you have multiple CPUs.
-- 
Roedy Green Canadian Mind Products http://mindprod.com
One thing I love about having a website, is that when I complain about
something, I only have to do it once. It saves me endless hours of 
grumbling.

Thread

synchronized methods "under the hood" bob smith <bob@coolfone.comze.com> - 2013-03-05 09:02 -0800
  Re: synchronized methods "under the hood" Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2013-03-05 09:15 -0800
  Re: synchronized methods "under the hood" Jan Burse <janburse@fastmail.fm> - 2013-03-05 18:59 +0100
    Re: synchronized methods "under the hood" Jan Burse <janburse@fastmail.fm> - 2013-03-05 19:16 +0100
    Re: synchronized methods "under the hood" Jan Burse <janburse@fastmail.fm> - 2013-03-06 15:24 +0100
  Re: synchronized methods "under the hood" Roedy Green <see_website@mindprod.com.invalid> - 2013-03-05 12:19 -0800
    Re: synchronized methods "under the hood" Sven Köhler <remove-sven.koehler@gmail.com> - 2013-03-05 23:44 +0100
      Re: synchronized methods "under the hood" Roedy Green <see_website@mindprod.com.invalid> - 2013-03-06 04:28 -0800
        Re: synchronized methods "under the hood" Jan Burse <janburse@fastmail.fm> - 2013-03-06 15:20 +0100

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