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Re: C++ threads versus PThreads for embedded Linux on ARM micro

From David Brown <david.brown@hesbynett.no>
Newsgroups comp.arch.embedded
Subject Re: C++ threads versus PThreads for embedded Linux on ARM micro
Date 2018-07-31 09:21 +0200
Organization A noiseless patient Spider
Message-ID <pjp2l1$4c7$1@dont-email.me> (permalink)
References <ddc2da65-65a3-4307-b93b-5ad1cc62a418@googlegroups.com> <b28cf52f-2a9e-4e6a-9f3f-8b9921c3a0c1@googlegroups.com> <8490b5e0-bf86-413c-866e-8a10a3d87466@googlegroups.com>

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On 27/07/18 23:53, gp.kiwi@gmail.com wrote:
> Thanks.  What is an "event object"?  What is the best way to pass
> data asynchronously using a queue, on Linux?  I've read that
> lock-free data structures are easy to get wrong and best avoided and
> that the C++ thread library doesn't have any lock free data
> structures - mainly because there's too many variations to have a
> generalized data structure.


Lock-free data structures can range from very simple to very difficult,
and there can be huge differences depending on the details of the
structure.  A single-writer, single-reader fixed size queue is /easy/ -
it's just two atomic counters for "head" and "tail" and an array, with a
little care about memory ordering.  For single core embedded processors,
it's usually sufficient to just use "volatile" - for bigger systems,
C++11 or C11 atomics handle the details.

On the other hand, a queue that can have variable size, and more than
one reader or writer, quickly gets really complicated to handle
lock-free, and often it is much simpler, safer and cheaper to use a
lock.  On the third hand, if you have multiple cores you might want
lock-free again for scalability.

There is no simple answer here, and much depends on the details of
exactly what you are wanting.  As long as you ask general questions,
you'll only get general answers.

> 
> Can we use the "libcds" library and be confident that it will work
> correctly?
> 
> https://github.com/khizmax/libcds
> 
> 
> On Saturday, July 28, 2018 at 3:52:02 AM UTC+12, StateMachineCOM
> wrote:
>> Traditional threads, whichever way you package them (as C++
>> threads, p-threads or any other thread library), typically
>> correspond to the "shared-state concurrency and blocking" approach.
>> This approach is known to be problematic, and many experts in
>> concurrent programming recommend to drastically limit both sharing
>> and blocking according to the following three best practices:
> [snip]
>

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C++ threads versus PThreads for embedded Linux on ARM micro "gp.kiwi@gmail.com" <graeme.prentice@gmail.com> - 2018-07-20 04:01 -0700
  Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-07-20 20:19 +0200
    Re: C++ threads versus PThreads for embedded Linux on ARM micro graeme.prentice@gmail.com - 2018-07-20 15:54 -0700
      Re: C++ threads versus PThreads for embedded Linux on ARM micro Paul Rubin <no.email@nospam.invalid> - 2018-07-20 18:27 -0700
        Re: C++ threads versus PThreads for embedded Linux on ARM micro graeme.prentice@gmail.com - 2018-07-20 23:58 -0700
          Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-07-21 14:32 +0200
            Re: C++ threads versus PThreads for embedded Linux on ARM micro mac <acolvin@efunct.com> - 2018-07-26 19:37 +0000
          Re: C++ threads versus PThreads for embedded Linux on ARM micro Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2018-07-21 21:48 +0300
          Re: C++ threads versus PThreads for embedded Linux on ARM micro Rob Gaddi <rgaddi@highlandtechnology.invalid> - 2018-07-23 09:58 -0700
  Re: C++ threads versus PThreads for embedded Linux on ARM micro Les Cargill <lcargill99@comcast.com> - 2018-07-22 13:15 -0500
  Re: C++ threads versus PThreads for embedded Linux on ARM micro StateMachineCOM <statemachineguru@gmail.com> - 2018-07-27 08:51 -0700
    Re: C++ threads versus PThreads for embedded Linux on ARM micro "gp.kiwi@gmail.com" <graeme.prentice@gmail.com> - 2018-07-27 14:53 -0700
      Re: C++ threads versus PThreads for embedded Linux on ARM micro Paul Rubin <no.email@nospam.invalid> - 2018-07-27 15:23 -0700
      Re: C++ threads versus PThreads for embedded Linux on ARM micro StateMachineCOM <statemachineguru@gmail.com> - 2018-07-30 09:08 -0700
      Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-07-31 09:21 +0200
    Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-07-31 09:13 +0200
      Re: C++ threads versus PThreads for embedded Linux on ARM micro StateMachineCOM <statemachineguru@gmail.com> - 2018-07-31 15:16 -0700
        Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-01 07:53 +0200
        Re: C++ threads versus PThreads for embedded Linux on ARM micro pozz <pozzugno@gmail.com> - 2018-08-01 15:49 +0200
        Re: C++ threads versus PThreads for embedded Linux on ARM micro upsidedown@downunder.com - 2018-08-01 21:47 +0300
          Re: C++ threads versus PThreads for embedded Linux on ARM micro StateMachineCOM <statemachineguru@gmail.com> - 2018-08-01 12:11 -0700
            Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-01 20:23 +0100
            Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-02 12:24 +0200
              Re: C++ threads versus PThreads for embedded Linux on ARM micro upsidedown@downunder.com - 2018-08-02 16:14 +0300
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-02 16:43 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro StateMachineCOM <statemachineguru@gmail.com> - 2018-08-02 09:12 -0700
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-02 18:13 +0100
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-02 23:05 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro StateMachineCOM <statemachineguru@gmail.com> - 2018-08-02 14:22 -0700
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Niklas Holsti <niklas.holsti@tidorum.invalid> - 2018-08-03 10:14 +0300
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-03 10:22 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-02 23:48 +0100
                Re: C++ threads versus PThreads for embedded Linux on ARM micro upsidedown@downunder.com - 2018-08-02 19:56 +0300
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-02 18:14 +0100
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-02 23:12 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-02 23:52 +0100
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-03 10:28 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-03 11:21 +0100
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-03 13:51 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro upsidedown@downunder.com - 2018-08-03 09:11 +0300
                Re: C++ threads versus PThreads for embedded Linux on ARM micro George Neuner <gneuner2@comcast.net> - 2018-08-04 03:00 -0400
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Robert Wessel <robertwessel2@yahoo.com> - 2018-08-02 12:23 -0500
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-02 23:13 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro George Neuner <gneuner2@comcast.net> - 2018-08-04 03:08 -0400
              Re: C++ threads versus PThreads for embedded Linux on ARM micro Robert Wessel <robertwessel2@yahoo.com> - 2018-08-02 12:23 -0500
              Re: C++ threads versus PThreads for embedded Linux on ARM micro George Neuner <gneuner2@comcast.net> - 2018-08-02 14:15 -0400
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-02 19:21 +0100
                Re: C++ threads versus PThreads for embedded Linux on ARM micro David Brown <david.brown@hesbynett.no> - 2018-08-02 23:18 +0200
                Re: C++ threads versus PThreads for embedded Linux on ARM micro Tom Gardner <spamjunk@blueyonder.co.uk> - 2018-08-03 00:02 +0100
          Re: C++ threads versus PThreads for embedded Linux on ARM micro StateMachineCOM <statemachineguru@gmail.com> - 2018-08-01 12:28 -0700

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