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Re: Multithreading

From rbowman <bowman@montana.com>
Newsgroups comp.lang.c
Subject Re: Multithreading
Date 2018-12-16 21:00 -0700
Message-ID <g7ol8vFu0u7U1@mid.individual.net> (permalink)
References <5c16c53f.660858109@news.xmission.com>

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On 12/16/2018 02:48 PM, Scott wrote:
> What I'd like to ask for are recommendations on resources for learning
> about the principles and pitfalls of threaded programming, in a
> general way, not tied to any specific implementation. I'm muddling my
> way through this exercise, but I have this feeling that I'm taking a
> Sunday stroll through a live minefield and just haven't managed to
> walk into anything really interesting yet.

Oh, there are definitely mines...

https://www.thegeekstuff.com/2012/05/c-mutex-examples/?refcom

That's one of the first pages I hit. There may be better examples but it 
does discuss one of the major minefields. Logically threads can simplify 
the code. For example, you can thread off something to read from a 
socket. It can block, no big deal, so you don't have to go to a 
non-blocking socket, select statements, and all that good stuff to keep 
the ball rolling.

Where it gets tricky is when it has read data from a socket and now has 
to pass it to another thread. Lets say you want to insert it into a 
linked list to be consumed by the other thread. The other thread is 
blissfully unaware of the socket reader and is happily processing the 
list and doing something with the data. Somebody has to say 'hey, I'm 
modifying the list' with the other thread waiting for its turn.

You need to watch out for deadlocks or both threads wind up politely 
waiting on each other.

It can bite you at odd moments. I'm old school and like to salt the code 
with fprintf's to a log file while I developing so I can construct a 
narrative of what's supposed to be happening. Even that needs to be set 
up with a mutex so the threads aren't simultaneously trying to write to 
the same log.

It's really not that complicated and you just need to think about where 
each thread will interact with a common object and keep them playing 
nicely together.

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Thread

Multithreading nobody@example.org (Scott) - 2018-12-16 21:48 +0000
  Re: Multithreading Joey Pabalinas <joeypabalinas@gmail.com> - 2018-12-16 17:11 -1000
  Re: Multithreading rbowman <bowman@montana.com> - 2018-12-16 21:00 -0700
  Re: Multithreading Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-12-17 22:19 +0000
    Re: Multithreading Joey Pabalinas <joeypabalinas@gmail.com> - 2018-12-17 12:45 -1000
    Re: Multithreading nobody@example.org (Scott) - 2018-12-19 19:48 +0000
      Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-19 11:58 -0800
      Re: Multithreading Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-12-19 23:17 +0000
        Re: Multithreading "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-19 15:31 -0800
          Re: Multithreading "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-19 15:34 -0800
        Re: Multithreading nobody@example.org (Scott) - 2018-12-22 10:43 +0000
          Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-22 03:41 -0800
            Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-22 03:46 -0800
          Re: Multithreading Thiago Adams <thiago.adams@gmail.com> - 2018-12-22 07:14 -0800
          Re: Multithreading rbowman <bowman@montana.com> - 2018-12-22 11:41 -0700
            Re: Multithreading "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-22 16:09 -0800
          Re: Multithreading scott@slp53.sl.home (Scott Lurndal) - 2018-12-22 19:52 +0000
            Re: Multithreading "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-22 16:10 -0800
            Re: Multithreading nobody@example.org (Scott) - 2018-12-23 23:11 +0000
              Re: Multithreading "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-23 15:24 -0800
                Re: Multithreading "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-23 15:25 -0800
                Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-24 02:05 -0800
              Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-24 02:08 -0800
  Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-18 07:18 -0800
    Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-18 07:51 -0800
      Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-19 09:24 -0800
        Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-19 09:55 -0800
          Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-19 11:02 -0800
            Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-19 11:16 -0800
              Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-19 11:25 -0800
          Re: Multithreading "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-19 15:37 -0800
            Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-19 16:03 -0800
              Re: Multithreading fir <profesor.fir@gmail.com> - 2018-12-20 08:02 -0800

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